Behavioral Neuroscience via MedWorm.com

An NMDA antagonist in the MPOA impairs copulation and stimulus sensitization in male rats.

Behavioral Neuroscience — Mon, 30 Jan 2012 05:00:00 +0100

We report here that the NMDA antagonist MK-801, microinjected into the MPOA, impaired copulatory behavior in sexually naïve as well as experienced males. In rats tested both as naïve and after sexual experience, drug treatment produced more profound impairment in naïve males. In addition, MK-801, microinjected into the MPOA before each of 7 noncopulatory exposures to receptive female rats, resulted in copulatory impairments on a drug-free test on Day 8, relative to aCSF-treated rats; their behavior was similar to that of males that had not been preexposed to females. Therefore, NMDA receptors in the MPOA contribute to the control of copulation and stimulus sensitization. Glutamate, acting via NMDA receptors, regulates many neural functions, including neuronal plasticity. This is the fir...

The relationship between cortisol, salivary alpha-amylase, and cognitive bias in young women.

Behavioral Neuroscience — Mon, 30 Jan 2012 05:00:00 +0100

Both animal and human studies suggest that cognitive bias toward negative information, such as that observed in major depression, may arise through the interaction of cortisol (CORT) and norepinephrine (NE) within the amygdala. To date, there is no published account of the relationship between endogenous NE and CORT levels and cognitive bias. The present study examined salivary CORT and salivary alpha-amylase (sAA), an indirect measure of NE, in relation to masked affective priming of words in young female participants. Women with higher salivary CORT showed increased priming to negative word pairs only when sAA was also high; when sAA was low, no effect of CORT on priming was observed. These results are in line with previous research indicating that increased CORT is linked to enhanced pr...

Early androgen effects on spatial and mechanical abilities: Evidence from congenital adrenal hyperplasia.

Behavioral Neuroscience — Mon, 30 Jan 2012 05:00:00 +0100

There is considerable controversy about the origins of sex differences in cognitive abilities, particularly the male superiority in spatial abilities. We studied effects of early androgens on spatial and mechanical abilities in adolescents and young adults with congenital adrenal hyperplasia (CAH). On tests of three-dimensional mental rotations, geography, and mechanical knowledge, females with CAH scored higher than their unaffected sisters, and males with CAH scored lower than their unaffected brothers. Exploratory regression analyses suggest that androgens affect spatial ability in females directly and through male-typed activity interests. Findings indicate that early androgens influence spatial and mechanical abilities, and that androgen effects on abilities may occur in part through ...

Building a better hormone therapy? How understanding the rapid effects of sex steroid hormones could lead to new therapeutics for age-related memory decline.

Behavioral Neuroscience — Mon, 30 Jan 2012 05:00:00 +0100

A wealth of data collected in recent decades has demonstrated that ovarian sex-steroid hormones, particularly 17β-estradiol (E2), are important trophic factors that regulate the function of cognitive regions of the brain such as the hippocampus. The loss of hormone cycling at menopause is associated with cognitive decline and dementia in women, and the onset of memory decline in animal models. However, hormone therapy is not currently recommended to prevent or treat cognitive decline, in part because of its detrimental side effects. In this article, it is proposed that investigations of the rapid effects of E2 on hippocampal function be used to further the design of new drugs that mimic the beneficial effects of E2 on memory without the side effects of current therapies. A conceptual mode...

Estrogen effects on the brain: Actions beyond the hypothalamus via novel mechanisms.

Behavioral Neuroscience — Mon, 30 Jan 2012 05:00:00 +0100

From its origins in how the brain controls the endocrine system via the hypothalamus and pituitary gland, neuroendocrinology has evolved into a science that now includes hormone action on many aspects of brain function. These actions involve the whole central nervous system and not just the hypothalamus. Advances in our understanding of cellular and molecular actions of steroid hormones have gone beyond the important cell nuclear actions of steroid hormone receptors to include signaling pathways that intersect with other mediators such as neurotransmitters and neuromodulators. This has, in turn, broadened the search for and identification of steroid receptors to include nonnuclear sites in synapses, dendrites, mitochondria, and glial cells, as well as cell nuclei. The study of estrogen rec...

Introduction to the special section on “Hormones and cognition: Perspectives, controversies, and challenges for future research”.

Behavioral Neuroscience — Mon, 30 Jan 2012 05:00:00 +0100

The research of the past two decades has firmly established that hormones modulate numerous aspects of cognitive function, including memory, attention, decision-making, and sensory processing. That such a wide variety of hormones influence cognition mediated by multiple nonhypothalamic brain regions illustrates the critical importance of hormones to neural and cognitive function. The diversity of hormonal effects on cognition is evident in the collection of reviews and original research articles assembled for this special section. Together, these articles provide an overview of recent research on varied topics in hormones and cognition, address controversial issues in the field, and discuss challenges that must be overcome in future research to gain a better understanding of the mechanisms...

Effects of prior light exposure on early evening performance, subjective sleepiness, and hormonal secretion.

Behavioral Neuroscience — Mon, 26 Dec 2011 05:00:00 +0100

In sighted humans, light intensity, timing, exposure duration, and spectral composition of light are important to entrain the endogenous circadian pacemaker to the 24-h day-night cycle. We tested the impact of two realistic office lighting conditions during the afternoon on subjective sleepiness, hormonal secretion, and cognitive performance in the early evening hours. Twenty-nine young subjects came twice and spent 8 h (12:00–20:00) in our laboratory, where they were exposed for 6 h to either artificial light (AL) or to mainly daylight (DL). In the early evening, we assessed their salivary cortisol and melatonin secretion, subjective sleepiness, and cognitive performance (n-back test) under dim light conditions. Subjects felt significantly more alert at the beginning of the evening afte...

Correction to Taylor et al. (2011).

Behavioral Neuroscience — Mon, 26 Dec 2011 05:00:00 +0100

This article contains several production-related errors. The title of the article was incorrectly set as “Differential Brain-Derived Neurotrophic Factor Expression in Limbic Brain Regions Following Social Defeat of Territorial Aggression.” In addition, the publication year for Fiore et al. (2003) on p. 912 was listed as 2004. Also on p. 916, the publication year for Xu et al. (2000) was listed as 2004 and on p. 918 Razzoli et al. (2011b), the b was omitted. (The following abstract of the original article appeared in record 2011-27519-008 .) Syrian hamsters readily form dominant-subordinate relationships under laboratory conditions. Winning or losing in agonistic encounters can have striking, long-term effects on social behavior, but the mechanisms underlying this experience-induced be...

To modulate and be modulated: Estrogenic influences on auditory processing of communication signals within a socio-neuro-endocrine framework.

Behavioral Neuroscience — Mon, 26 Dec 2011 05:00:00 +0100

Gonadal hormones modulate behavioral responses to sexual stimuli, and communication signals can also modulate circulating hormone levels. In several species, these combined effects appear to underlie a two-way interaction between circulating gonadal hormones and behavioral responses to socially salient stimuli. Recent work in songbirds has shown that manipulating local estradiol levels in the auditory forebrain produces physiological changes that affect discrimination of conspecific vocalizations and can affect behavior. These studies provide new evidence that estrogens can directly alter auditory processing and indirectly alter the behavioral response to a stimulus. These studies show that: 1) Local estradiol action within an auditory area is necessary for socially relevant sounds to indu...

Once a mother, always a mother: Maternal experience protects females from the negative effects of stress on learning.

Behavioral Neuroscience — Mon, 19 Dec 2011 05:00:00 +0100

Women experience profound hormonal fluctuations throughout their reproductive lives. They are especially susceptible to disturbances in mood and cognition during the transition from pregnancy into postpartum and motherhood (Brummelte & Galea, 2010). Their behavioral and hormonal responses to stressful stimuli are also altered during this time. These changes are not limited to humans but occur in many mammalian species. Virgin female rats express a severe learning deficit in associative eyeblink conditioning after a stressful life event (Wood, Beylin, & Shors, 2001; Wood & Shors, 1998), but lactating females or those that are caring for young learn well even after the stressor (Leuner & Shors, 2006). However, we do not know whether maternal experience persistently alters learning after a st...

Effects of the val(158)met catechol-o-methyltransferase gene polymorphism on olfactory processing in schizophrenia.

Behavioral Neuroscience — Mon, 12 Dec 2011 05:00:00 +0100

The catechol-O-methyltransferase (COMT) val158met polymorphism has received attention in schizophrenia due to its role in prefrontal dopamine catabolism. Given the rich dopaminergic innervations of the olfactory bulb and the influence of dopamine on the transmission of olfactory signals, the authors examined the influence of COMT genotype status on the olfactory processing impairment observed in schizophrenia. The University of Pennsylvania Smell Identification Test was administered unirhinally to individuals with schizophrenia (n = 42) and a demographically matched sample of healthy controls (n = 30). Individuals were genotyped for the COMT val158met polymorphism. A statistically significant interaction of diagnosis and COMT genotype was observed, such that schizophrenia heterozygotes and...

Event-specific enhancement of memory via brief electrical stimulation to the basolateral complex of the amygdala in rats.

Behavioral Neuroscience — Mon, 05 Dec 2011 05:00:00 +0100

The basolateral complex of the amygdala (BLA) modulates memory for emotional events, and direct activation of the BLA following a learning session can enhance subsequent memory. Yet optimal enhancement of episodic memory during emotional events would likely require that BLA activation occur close in time to the event and to be brief enough to target specific memories if some events are to be remembered better than others. In the present study, rats were given a novel object recognition memory task in which initial encounters with some of the objects were immediately followed by brief electrical stimulation of the BLA, and these objects were remembered better one day later as compared to objects for which the initial encounter was not followed by stimulation. The results indicated that BLA ...

Stress-induced cortisol facilitates threat-related decision making among police officers.

Behavioral Neuroscience — Mon, 05 Dec 2011 05:00:00 +0100

Previous research suggests that cortisol can affect cognitive functions such as memory, decision making, and attentiveness to threat-related cues. Here, we examine whether increases in cortisol, brought on by an acute social stressor, influence threat-related decision making. Eighty-one police officers completed a standardized laboratory stressor and then immediately completed a computer simulated decision-making task designed to examine decisions to accurately shoot or not shoot armed and unarmed Black and White targets. Results indicated that police officers who had larger cortisol increases to the social-stress task subsequently made fewer errors when deciding to shoot armed Black targets relative to armed White targets, suggesting that hypothalamic pituitary adrenal (HPA) activation ma...

Long-term replacement of estrogen in combination with medroxyprogesterone acetate improves acquisition of an alternation task in middle-aged female rats.

Behavioral Neuroscience — Mon, 05 Dec 2011 05:00:00 +0100

This study, in combination with previous research, indicates that hormone effects cannot be generalized across tasks, age, or duration, and long-term estrogen in combination with MPA can be beneficial for some tasks. (PsycINFO Database Record (c) 2012 APA, all rights reserved) (Source: Behavioral Neuroscience)

Interplay of oxytocin, vasopressin, and sex hormones in the regulation of social recognition.

Behavioral Neuroscience — Mon, 05 Dec 2011 05:00:00 +0100

Social Recognition is a fundamental skill that forms the basis of behaviors essential to the proper functioning of pair or group living in most social species. We review here various neurobiological and genetic studies that point to an interplay of oxytocin (OT), arginine-vasopressin (AVP), and the gonadal hormones, estrogens and testosterone, in the mediation of social recognition. Results of a number of studies have shown that OT and its actions at the medial amygdala seem to be essential for social recognition in both sexes. Estrogens facilitate social recognition, possibly by regulating OT production in the hypothalamus and the OT receptors at the medial amygdala. Estrogens also affect social recognition on a rapid time scale, likely through nongenomic actions. The mechanisms of these ...

Differential brain-derived neurotrophic factor expression in limbic brain regions following social defeat or territorial aggression.

Behavioral Neuroscience — Mon, 28 Nov 2011 05:00:00 +0100

[Correction Notice: An erratum for this article was reported online in Behavioral Neuroscience on Dec 26 2011 (see record 2011-29775-001 ). The title of the article was incorrectly set as “Differential Brain-Derived Neurotrophic Factor Expression in Limbic Brain Regions Following Social Defeat of Territorial Aggression.” In addition, the publication year for Fiore et al. (2003) on p. 912 was listed as 2004. Also on p. 916, the publication year for Xu et al. (2000) was listed as 2004 and on p. 918 Razzoli et al. (2011b), the b was omitted.] Syrian hamsters readily form dominant-subordinate relationships under laboratory conditions. Winning or losing in agonistic encounters can have striking, long-term effects on social behavior, but the mechanisms underlying this experience-induced b...

Rodent estrous cycle response to incomplete spinal cord injury, surgical interventions, and locomotor training.

Behavioral Neuroscience — Mon, 28 Nov 2011 05:00:00 +0100

Estrous cycle disruption after spinal cord injury (SCI) in female rats is a common phenomenon. It remains unknown, however, if the aberrant estrous cycle is a result of an injury to the spinal cord itself or due to the general stress associated with surgical interventions. We addressed this issue by determining estrous cyclicality in female rats after a spinal cord hemisection (HX), implantation of EMG wires into selected hind limb muscles, and/or injections of tracer dyes into the spinal cord. Because it is known that aerobic exercise can enhance the recovery of locomotor function in rodents with an incomplete SCI, we also determined if locomotor training positively impacts the disrupted estrous cycle after an HX. Estrous cycle assessments were made during a 5–8 week period in 27 female...

Differential brain-derived neurotrophic factor expression in limbic brain regions following social defeat of territorial aggression.

Behavioral Neuroscience — Mon, 28 Nov 2011 05:00:00 +0100

Syrian hamsters readily form dominant-subordinate relationships under laboratory conditions. Winning or losing in agonistic encounters can have striking, long-term effects on social behavior, but the mechanisms underlying this experience-induced behavioral plasticity are unclear. The present study tested the hypothesis that changes in brain-derived neurotrophic factor (BDNF) may at least in part mediate this plasticity. Male hamsters were paired for 15-min using a resident-intruder model, and individuals were identified as winners or losers on the basis of their behavior. BDNF was examined with in situ hybridization 2 hr after treatment during the consolidation period of emotional learning. Losing animals had significantly more BDNF mRNA in the basolateral (BLA) and medial (MeA) nuclei of ...

Social facial touch in rats.

Behavioral Neuroscience — Mon, 28 Nov 2011 05:00:00 +0100

We know much about how rats use their whiskers to discriminate simple tactile properties, but little about how they are used in natural settings. Here we studied whisker motion during social interactions between rats in order to gain a better understanding of natural whisker use in this model system for sensorimotor integration. In the first set of experiments, an intruder was placed in a second rat's home cage. Anogenital sniffing immediately ensued; later in the trial, facial interactions occurred at least as frequently. Whereas much previous work has focused on the importance of anogenital sniffing during social interactions, these facial interactions were accompanied by some of the most intense whisker behaviors described to date. Whisker trimming increased biting but reduced boxing. I...

Nonlinear temporal integration of brain stimulation reward.

Behavioral Neuroscience — Mon, 28 Nov 2011 05:00:00 +0100

A good deal is known about psychological factors that contribute to reward value, but very little is known about how reward is computed in the brain. Integration in the circuit for brain stimulation reward may provide a simple model system. Parametric studies have favored the idea that the integration is linear, although a few have suggested that it involves adaptation. However, these studies have generally not focused on relevance to psychological factors such as temporal discounting of reward. To begin to address these issues, I gave rats a choice between a simple train of 2 seconds of stimulation at a uniform frequency and a compound train of 1 second of stimulation at either 50, 150, or 250 Hz immediately followed by 1 second of stimulation at 50, 150, or 250 Hz, for a total of nine co...

Effects of chronic intermittent ethanol exposure on orbitofrontal and medial prefrontal cortex-dependent behaviors in mice.

Behavioral Neuroscience — Mon, 28 Nov 2011 05:00:00 +0100

In humans, stroke or trauma-induced damage to the orbitofrontal cortex (OFC) or medial prefrontal cortex (mPFC) results in impaired cognitive flexibility. Alcoholics also exhibit similar deficits in cognitive flexibility, suggesting that the OFC and mPFC are susceptible to alcohol-induced dysfunction. The present experiments investigated this issue using an attention set-shifting assay in ethanol dependent adult male C57BL/6J mice. Ethanol dependence was induced by exposing mice to repeated cycles of chronic intermittent ethanol (CIE) vapor inhalation. Behavioral testing was conducted 72 hours or 10 days following CIE exposure to determine whether ethanol-induced changes in OFC-dependent (reversal learning) and mPFC-dependent (set-shifting) behaviors are long lasting. During early ethanol ...

Reevaluating hippocampus-dependent learning in FVB/N mice.

Behavioral Neuroscience — Mon, 28 Nov 2011 05:00:00 +0100

In this study, we compared FVB mice to the well-characterized C57BL/6 (B6) strain in a battery of hippocampus-dependent tasks that had several nonvisual cues. The tasks included: trace eyeblink conditioning, spontaneous alternation in the Y maze, social recognition, trace and contextual fear conditioning, and odor habituation–dishabituation. FVB mice were able to learn all the tasks, often to similar levels as B6 mice. In contrast to previous reports, our data suggest FVB mice are not cognitively deficient with temporal memory tasks, when the tasks do not rely heavily upon vision. Thus, the FVB strain may be used as the genetic background for behavioral phenotyping when nonvisual hippocampal-dependent tasks are utilized. (PsycINFO Database Record (c) 2011 APA, all rights reserved) (Sourc...

Age-associated deficits in pattern separation functions of the perirhinal cortex: A cross-species consensus.

Behavioral Neuroscience — Mon, 28 Nov 2011 05:00:00 +0100

Normal aging causes a decline in object recognition. Importantly, lesions of the perirhinal cortex produce similar deficits and also lead to object discrimination impairments when the test objects share common features, suggesting that the perirhinal cortex participates in perceptual discrimination. The current experiments investigated the ability of young and aged animals to distinguish between objects that shared features with tasks with limited mnemonic demands. In the first experiment, young and old rats performed a variant of the spontaneous object recognition task in which there was a minimal delay between the sample and the test phase. When the test objects did not share any features (“Easy” perceptual discrimination) both young and aged rats correctly identified the novel objec...

Deficits in attentional control: Cholinergic mechanisms and circuitry-based treatment approaches.

Behavioral Neuroscience — Mon, 28 Nov 2011 05:00:00 +0100

The cognitive control of attention involves maintaining task rules in working memory (or “online”), monitoring reward and error rates, filtering distractors, and suppressing prepotent, and competitive responses. Weak attentional control increases distractibility and causes attentional lapses, impulsivity, and attentional fatigue. Levels of tonic cholinergic activity (changes over tens of seconds or minutes) modulate cortical circuitry as a function of the demands on cognitive control. Increased cholinergic modulation enhances the representation of cues, by augmenting cue-evoked activity in thalamic glutamatergic afferents, thereby increasing the rate of detection. Such cholinergic modulation is mediated primarily via α4β2* nicotinic acetylcholine receptors. Animal experiments and cli...

Memory modulation.

Behavioral Neuroscience — Mon, 28 Nov 2011 05:00:00 +0100

Our memories are not all created equally strong: Some experiences are well remembered while others are remembered poorly, if at all. Research on memory modulation investigates the neurobiological processes and systems that contribute to such differences in the strength of our memories. Extensive evidence from both animal and human research indicates that emotionally significant experiences activate hormonal and brain systems that regulate the consolidation of newly acquired memories. These effects are integrated through noradrenergic activation of the basolateral amygdala that regulates memory consolidation via interactions with many other brain regions involved in consolidating memories of recent experiences. Modulatory systems not only influence neurobiological processes underlying the c...

Correction to Eilam-Stock et al. (2011).

Behavioral Neuroscience — Mon, 21 Nov 2011 05:00:00 +0100

We examined the effects of acute BPA administration (40 μg/kg) on memory and synaptic plasticity in adult male rats. BPA significantly impaired both visual and spatial memory and decreased dendritic spine density on pyramidal cells in CA1 and the medial prefrontal cortex (mPFC). Additionally, BPA significantly decreased PSD-95, a synaptic marker, in the hippocampus and increased cytosolic pCREB, a transcription factor, in mPFC. Together, these findings show that a single dose of BPA, below the USEPA reference safe daily limit of 50 μg/kg/day, may block the formation of new memories by interfering with neural plasticity processes in the adult brain. (PsycINFO Database Record (c) 2012 APA, all rights reserved) (Source: Behavioral Neuroscience)

Impairment of recovery from incentive downshift after lesions of the anterior cingulate cortex: Emotional or cognitive deficits?

Behavioral Neuroscience — Mon, 24 Oct 2011 04:00:00 +0100

The anterior cinculate cortex (ACC) is known to be implicated in pain-fear and reward expectations. Animals were given electrolytic lesions of the ACC and then trained in the consummatory successive negative contrast (cSNC) situation. In cSNC, animals exposed to an incentive downshift from 32% to 4% sucrose exhibit less consummatory behavior than animals always exposed to 4% sucrose. The ACC lesion had no measurable effects on the consummatory performance of animals before the downshift (i.e., the lesion did not affect consumption of 32% vs. 4% sucrose); on the performance of unshifted, 4% sucrose animals; and on the first downshift trial. However, ACC animals exhibited a significant retardation of recovery from cSNC relative to downshifted shams. Within-trial analysis of consummatory beha...

Higher reported saturated fat and refined sugar intake is associated with reduced hippocampal-dependent memory and sensitivity to interoceptive signals.

Behavioral Neuroscience — Mon, 24 Oct 2011 04:00:00 +0100

Regulation of energy intake depends in part on both memory for prior food intake and internal signals of hunger and satiety. These functions are both mediated by the hippocampus, a brain structure that animal studies have shown to be impaired after maintenance on high fat and refined sugar (HFS) diets. Study 1, using a cross-sectional design, revealed that self-reported HFS diet was associated with poorer performance on hippocampal sensitive memory tasks but not other neuropsychological control measures. Study 2 replicated this finding in two groups selected to differ in HFS intake, additionally showing that this effect is specific to hippocampal functioning and does not extend to measures of prefrontal cortex function. Furthermore, in a laboratory-based test of food intake, the HFS rich d...

Bisphenol-A impairs memory and reduces dendritic spine density in adult male rats.

Behavioral Neuroscience — Mon, 17 Oct 2011 04:00:00 +0100

Chronic stress and a cyclic regimen of estradiol administration separately facilitate spatial memory: Relationship with hippocampal CA1 spine density and dendritic complexity.

Behavioral Neuroscience — Mon, 17 Oct 2011 04:00:00 +0100

This study investigated the effects of chronic restraint stress and repeated cyclic estradiol pulses on hippocampal CA3 and CA1 dendritic and/or spine morphology and spatial memory in female rats. Sprague-Dawley adult female rats were ovariectomized and then injected over 2 days with 17β-estradiol (10 μg, s.c.), which was repeated every 4–5 days. While all rats received similar estradiol injection histories, half of the rats were chronically restrained and/or given a final cyclic pulse of estradiol prior to testing on a hippocampal-dependent object placement (OP) task to assess spatial memory. OP testing was performed 2 days after the last restraint session, as well as when the last 2 estradiol pulses best captured the maximal effect on hippocampal CA1 spine density. The data revealed ...

Estrogen and cognitive functioning in women: Lessons we have learned.

Behavioral Neuroscience — Mon, 17 Oct 2011 04:00:00 +0100

Extant research findings allow several conclusions regarding the relationship between estrogen and cognitive functioning across the female life span. First, performance on tests of verbal memory fluctuates in concert with physiological changes in ovarian hormone production during the menstrual cycle and during pregnancy and the postpartum period. Estrogen therapy (ET) prevents the decrease in verbal memory when administered immediately following the surgical removal of both ovaries in premenopausal women. Some, but relatively little evidence is available to support the idea that ET, initiated at the time of a natural or a surgical menopause for a few years, may protect against cognitive decline 30 years later and more research in this area is urgently needed. Finally, the evidence to date ...

Conditioned inhibition in a rodent model of attention-deficit/hyperactivity disorder.

Behavioral Neuroscience — Mon, 17 Oct 2011 04:00:00 +0100

A deficit in inhibition may underlie some of the symptoms of attention-deficit/hyperactivity disorder (ADHD), particularly impulsivity. However, the data on inhibitory deficits in children with ADHD are mixed. Moreover, there has been little characterization of inhibitory processes in animal models of ADHD. Pavlov's conditioned inhibition procedure allows a direct assessment of the inhibitory status of a stimulus via summation and retardation tests. Therefore, in the current study, we examined conditioned inhibition in spontaneously hypertensive rats (SHRs), the most well-validated animal model of ADHD. SHRs and Wistar rats were trained in a simultaneous feature-negative discrimination in eyeblink conditioning. Each session consisted of a mixture of 2 trial types: a tone paired with a peri...

Risky business: Executive function, personality, and reckless behavior during adolescence and emerging adulthood.

Behavioral Neuroscience — Mon, 17 Oct 2011 04:00:00 +0100

Adolescence is a risky business. Despite outstanding physical health, the risk of injury or death during adolescence is 2–3 times that of childhood. The primary cause of this increase in morbidity and mortality is heightened risky behavior including drinking, driving, drug-taking, smoking, and unprotected sex. Why is it that some adolescents take big risks, while others do not? One potential source of individual differences in risk-taking behavior may lie in individual differences in executive function including judgment, impulse control, self-monitoring, and planning. Researchers have hypothesized that limited brain system integration and efficiency, particularly in the prefrontal cortex and related structures, may be involved in the range and degree of risky behavior commonly exhibited...

Comprehensive motor testing in Fmr1-KO mice exposes temporal defects in oromotor coordination.

Behavioral Neuroscience — Mon, 17 Oct 2011 04:00:00 +0100

Fragile X syndrome (FXS; MIM #300624), a well-recognized form of inherited human mental retardation is caused, in most cases, by a CGG trinucleotide repeat expansion in the 5′-untranslated region of FMR1, resulting in reduced expression of the fragile X mental retardation protein (FMRP). Clinical features include macroorchidism, anxiety, mental retardation, motor coordination, and speech articulation deficits. The Fmr1 knockout (Fmr1-KO) mouse, a mouse model for FXS, has been shown to replicate the macroorchidism, cognitive deficits, and neuroanatomical abnormalities found in human FXS. Here we asked whether Fmr1-KO mice also display appendicular and oromotor deficits comparable to the ataxia and dysarthric speech seen in FXS patients. We employed standard motor tests for balance and app...

A history of bingeing on fat enhances cocaine seeking and taking.

Behavioral Neuroscience — Mon, 10 Oct 2011 04:00:00 +0100

Binge eating and substance dependence are disorders characterized by a loss of control over consummatory behaviors. Given the common characteristics of these two types of disorders, it is not surprising that the comorbidity between eating disorders and substance abuse disorders is high (20–40%; Conason et al., 2006). It is unknown, however, whether loss of control in one disorder predisposes an individual to loss of control in the other. The present study, therefore, used a rodent model to test whether a history of binge eating would augment subsequent responding for cocaine. Using the limited access protocol described by Corwin et al. (1998), 45 adult male Sprague–Dawley rats were maintained on one of four dietary protocols for a period of six weeks: chow only (Chow; n = 9), continuou...

Neonatal amygdala lesions result in globally blunted affect in adult rhesus macaques.

Behavioral Neuroscience — Mon, 10 Oct 2011 04:00:00 +0100

The amygdala has been implicated in affective and social processing for more than a century. Animals with damage to the amygdala have altered affective and social behavior patterns, though the precise nature of these behavioral changes depends on a number of factors including lesion technique, age of the subject at the time of lesion, rearing, and housing environments. Interpretations of amygdala lesion studies are further complicated by the potentially confounded nature of affective and social stimuli (e.g., social interactions with a conspecific partner that is consistently aggressive). In the present study, we evaluated affective responding to affectively and socially evocative video stimuli in a group of rhesus macaques that received bilateral amygdala lesions as neonates. The stimuli ...

Endocrine substrates of cognitive and affective changes during pregnancy and postpartum.

Behavioral Neuroscience — Mon, 03 Oct 2011 04:00:00 +0100

Pregnancy and motherhood constitute periods of tremendous hormonal variation that orchestrate parturition, lactation, maternal care, maternal aggression, and recognition of offspring, among other functions. Cognitive processing also varies during pregnancy and motherhood and may serve an adaptive function in preparation for parturition and rearing. Additionally, maternal experience may have enduring consequences for the brain, behavior, and cognition long after offspring are mature. However, the early postpartum period also renders women psychologically vulnerable as approximately 15% of women experience postpartum depression, with estimates of 50–80% reporting a milder form of depression termed “maternal blues.” This review will present literature on pregnancy- and parity-related ch...

Capacity of visual classical conditioning in Drosophila larvae.

Behavioral Neuroscience — Mon, 03 Oct 2011 04:00:00 +0100

In this study, Drosophila larvae were used as a simple model to study visual classical conditioning. We show that larvae are able to associate positive or negative cues with either light or darkness, thus changing their native light-preference. This effect can be robustly provoked through gustatory stimuli and electric shock. We further show that light can not only be used as a conditioned stimulus but also as an unconditioned stimulus, as punishment in the olfactory classical conditioning procedure, possibly forming two different kinds of memories. Our findings show that even though larvae show a strong naïve response when exposed to light, the animals display a comparably large repertoire of visual memories that can be formed. Therefore, our study provides an impacting entry point into ...

Estradiol-dependent modulation of serotonergic markers in auditory areas of a seasonally breeding songbird.

Behavioral Neuroscience — Mon, 26 Sep 2011 04:00:00 +0100

In this study, we looked for evidence that E2-dependent modulation of auditory responses is mediated by serotonergic systems. In female nonbreeding white-throated sparrows treated with E2, the density of fibers immunoreactive for serotonin transporter innervating the auditory midbrain and rostral auditory forebrain increased compared with controls. E2 treatment also increased the concentration of the serotonin metabolite 5-HIAA in the caudomedial mesopallium of the auditory forebrain. In a second experiment, females exposed to 30 min of conspecific male song had higher levels of 5-HIAA in the caudomedial nidopallium of the auditory forebrain than birds not exposed to song. Overall, we show that in this seasonal breeder, (a) serotonergic fibers innervate auditory areas; (b) the density of t...

Similarities and differences in spatial learning and object recognition between young male C57Bl/6J mice and Sprague-Dawley rats.

Behavioral Neuroscience — Mon, 26 Sep 2011 04:00:00 +0100

Mice and rats are often used interchangeably in neuroscience research. However, species differences in brain structure and connectivity exist within the medial temporal lobe circuits that contribute to learning and memory. The hippocampus in particular contributes to both spatial learning and recognition memory, but the extent to which rats and mice are comparable in these two cognitive domains remains unclear. To evaluate potential species differences in spatial memory and object recognition, young adult male Sprague–Dawley rats and male C57Bl/6J mice were tested in the water maze and novel object recognition tasks. Following six days of training, with four trials per day, there was no difference in the ability of rats and mice to learn the location of a hidden platform. However, rats p...

The modulation of fragile X behaviors by the muscarinic M4 antagonist, tropicamide.

Behavioral Neuroscience — Mon, 26 Sep 2011 04:00:00 +0100

Muscarinic acetylcholine receptors (mAChR) are G protein–coupled receptors (M1–M5), grouped together into two functional classes, based on their G protein interaction. Although ubiquitously expressed in the CNS, the M4 protein shows highest expression in the neostriatum, cortex, and hippocampus. Electrophysiological and biochemical studies have provided evidence for overactive mAChR signaling in the fragile X knock-out (Fmr1KO) mouse model, and this has been hypothesized to contribute to the phenotypes seen in Fmr1KO mice. To address this hypothesis we used an M4 antagonist, tropicamide, to reduce the activity through the M4 mAChR and investigated the behavioral response in the Fmr1KO animals. Data from the marble-burying assay have shown that tropicamide treatment resulted in a decrea...

Comparative effects of different test day challenges on performance in the 5-choice serial reaction time task.

Behavioral Neuroscience — Mon, 26 Sep 2011 04:00:00 +0100

The 5-choice serial reaction time task (5-CSRTT) is a valuable cognitive test that permits the simultaneous assessment of several different cognitive modalities, including attention, impulse control, processing speed, and cognitive flexibility. Increasing task difficulty on test days through various challenges can further enhance the versatility of this test by selectively enhancing the cognitive load on different aspects of the task. Systematic comparisons of the effects of different test day challenges on 5-CSRTT performance are essential to verify how these challenges affect different task measures and which manipulations are best suited for future studies of different aspects of cognition. We trained Wistar rats in the 5-CSRTT under standard conditions, then challenged them on the test...

Administration of dehydroepiandrosterone (DHEA) enhances visual-spatial performance in postmenopausal women.

Behavioral Neuroscience — Mon, 26 Sep 2011 04:00:00 +0100

The current article examines the effect of administering dehydroepiandrosterone (DHEA) on visual-spatial performance in postmenopausal women (N = 24, ages 55–80). The concurrent reduction of serum DHEA levels and visual-spatial performance in this population, coupled with the documented effects of DHEA's androgenic metabolites on visual-spatial performance, suggests that DHEA administration may enhance visual-spatial performance. The current experiment used a double-blind, placebo-controlled crossover design in which 50 mg of oral DHEA was administered daily in the drug condition to explore this hypothesis. Performance on the Mental Rotation, Subject-Ordered Pointing, Fragmented Picture Identification, Perceptual Identification, Same-Different Judgment, and Visual Search tasks and serum ...

Dose-dependent effects of hydrocortisone infusion on autobiographical memory recall.

Behavioral Neuroscience — Mon, 26 Sep 2011 04:00:00 +0100

The glucocorticoid hormone cortisol has been shown to impair episodic memory performance. The present study examined the effect of two doses of hydrocortisone (synthetic cortisol) administration on autobiographical memory retrieval. Healthy volunteers (n = 66) were studied on two separate visits, during which they received placebo and either moderate-dose (0.15 mg/kg IV; n = 33) or high-dose (0.45 mg/kg IV; n = 33) hydrocortisone infusion. From 75 to 150 min post-infusion subjects performed an Autobiographical Memory Test and the California Verbal Learning Test (CVLT). The high-dose hydrocortisone administration reduced the percent of specific memories recalled (p = .04), increased the percent of categorical (nonspecific) memories recalled (p < .001), and slowed response times for categori...

Theta-burst stimulation of the right neocerebellar vermis selectively disrupts the practice-induced acceleration of lexical decisions.

Behavioral Neuroscience — Mon, 26 Sep 2011 04:00:00 +0100

The present study reports an experiment of cerebellar transcranial magnetic stimulation in a lexical decision task. In contrast to the study by Argyropoulos (2011), no effect of cerebellar stimulation was observed on priming sizes. However, when subjects confronted the same stimuli in the second session of participation, lexical decision latencies did not become any shorter after stimulation of the right neocerebellar vermis, in contrast to all other conditions. This finding is discussed in the light of current research in cerebellar cognitive and linguistic functions, and provides some first evidence for the recently entertained hypothesis that neocerebellar loci are significant in acquiring, storing, and retrieving associative memory traces of repeatedly co-occurring neural events in the...

Effects of cortical and striatal dopamine D1 receptor blockade on cued versus noncued behavioral responses.

Behavioral Neuroscience — Mon, 26 Sep 2011 04:00:00 +0100

We examined here whether D1 receptor blockade within striatal or frontal cortical DA target regions would differentially affect head entry responses elicited by an auditory cue compared with those occurring during noncued intertrial intervals. Rats received 2 drug-free 28-trial daily sessions in which an auditory cue was immediately followed by food delivery. On the following day, separate groups of rats received bilateral infusions of D1 antagonist SCH23390 to the dorsomedial striatum (DMS), nucleus accumbens (NAcc) core, or the medial prefrontal cortex (mPFC). SCH23390 infused into the DMS and NAcc core suppressed noncued head entries but had no effect on head entries in response to the auditory cue. SCH23390 infused to the mPFC did not reduce either cued or noncued approach responses. S...

Exploration of cerebellar-dependent associative learning in schizophrenia: Effects of varying and shifting interstimulus interval on eyeblink conditioning.

Behavioral Neuroscience — Mon, 26 Sep 2011 04:00:00 +0100

Eyeblink conditioning abnormalities have been reported in schizophrenia, but the extent to which these anomalies are evident across a range of delay intervals (i.e., interstimulus intervals; ISIs) is unknown. In addition, the effects of ISI shifts on learning are unknown, though such manipulations can be informative about the plasticity of cerebellar timing functions. Therefore, the primary purpose of the present study was to investigate the interactions between ISI manipulations and learning in schizophrenia. A standard delay eyeblink conditioning procedure with four different interstimulus intervals (ISIs; 250, 350, 550, 850 ms) was employed. Each eyeblink conditioning experiment was immediately followed by another with a different ISI, thus permitting the characterization of conditioned...

Hormones and cognitive functioning during late pregnancy and postpartum: A longitudinal study.

Behavioral Neuroscience — Mon, 19 Sep 2011 04:00:00 +0100

This longitudinal study investigated the possible influence of estradiol (E₂), progesterone (P), testosterone (T), cortisol (CORT), and prolactin (PRL) levels on cognitive functioning during late pregnancy and the early postpartum period. The performance of 55 pregnant women on a battery of neuropsychological tests, tested once during the third trimester of pregnancy and once during the early postpartum period, was compared with that of 21 nonpregnant controls matched for age and education. Women in the pregnancy group had significantly lower scores than the controls during both the pre- and postpartum visits on tasks of verbal recall and processing speed. CORT levels were significantly associated, in an inverted-U function, with verbal recall scores at both the pregnancy and at postpart...

Ingestion analgesia occurs when a bad taste turns good.

Behavioral Neuroscience — Mon, 19 Sep 2011 04:00:00 +0100

During ingestion of water, chocolate, sucrose, and saccharin, pain-related behaviors are suppressed. This ingestion analgesic effect is reversed when the hedonic valence of a food is switched from “good” to “bad” as occurs during conditioned taste aversion. Here, we tested the converse hedonic shift to determine if ingestion analgesia occurs when 0.3 M NaCl is made palatable by inducing a sodium appetite. In Experiment 1, sham- and sodium-depleted rats were tested for paw withdrawal and lick latencies to brief noxious heat during quiet wake and intraoral NaCl ingestion. Only sodium-depleted rats showed a suppression of heat-evoked reactions during NaCl ingestion. In Experiment 2, we tested whether this analgesic effect is mediated by the brainstem nucleus raphe magnus (NRM). Inacti...

Neonatal hippocampal lesions in rhesus macaques alter the monitoring, but not maintenance, of information in working memory.

Behavioral Neuroscience — Mon, 19 Sep 2011 04:00:00 +0100

Neonatal hippocampal damage in rodents impairs medial prefrontal working memory functions. To examine whether similar impairment will follow the same damage in primates, adult monkeys with neonatal hippocampal lesions and sham-operated controls were trained on two working memory tasks. The session-unique delayed nonmatch-to-sample (SU-DNMS) task measures maintenance of information in working memory mediated by the ventral lateral prefrontal cortex. The object self-ordered (Obj-SO) task measures monitoring of information in working memory mediated by the dorsolateral prefrontal cortex. Adult monkeys with neonatal hippocampal lesions performed as well as sham-operated controls on the SU-DNMS task at either the 5- or 30-s delays but were severely impaired on the Obj-SO task. These results ext...

Reactivation, interference, and reconsolidation: Are recent and remote memories likewise susceptible?

Behavioral Neuroscience — Mon, 29 Aug 2011 04:00:00 +0100

The retrieval of a consolidated, apparently stable memory can return it to a labile state, necessitating another period of stabilization, termed reconsolidation. During reconsolidation, memories are susceptible to modifications, thus providing the opportunity to change unwanted memories. In a test of whether the possibility to alter retrieved memories depends on the age of the memories, participants learned a set of emotional and neutral pictures and recalled it 1, 7, or 28 days later. Immediately after retrieval, participants learned a second set of pictures. Memory retrieval per se enhanced 28-day-old memories but had no effect on 1-day- or 7-day-old memories. Learning new pictures interfered with 1-day-old and 28-day-old memories but not with 7-day-old memories. Evidence for reconsolida...

Pseudoneglect and embryonic light stimulation in the avian brain.

Behavioral Neuroscience — Mon, 22 Aug 2011 04:00:00 +0100

A bias to allocate attention to the left hemispace, similar to the well-known pseudoneglect phenomenon shown by humans, has been recently reported in domestic chicks and other species of birds. Asymmetrical light exposure of the embryo of the domestic chick in a critical period before hatching is known to be responsible for a structural asymmetry in the visual ascending projections of the thalamofugal pathway and for lateralization of some visual behaviors. Thus the animal model provided by the chick makes possible investigation of the prenatal factors that may influence asymmetry in spatial attention. Here chicks coming from eggs exposed to light (light incubated, Li-chicks) and chicks incubated in darkness (dark incubated, Di-chicks) were tested in a task in which they were required to e...

Glutamate and the aggression neural circuit in adolescent anabolic steroid-treated Syrian hamsters (Mesocricetus auratus).

Behavioral Neuroscience — Mon, 22 Aug 2011 04:00:00 +0100

Adolescent exposure to anabolic androgenic steroids (AAS) alters the development and activity of the glutamate neural system in the latero-anterior hypothalamus (LAH) in hamsters (Mesocricetus auratus); that is, an important neural component of the adolescent AAS-induced aggressive response. In this article, we used retrograde tracing to investigate glutamate-specific alterations in the connections between the LAH and several other nuclei implicated in adolescent AAS-induced aggression. Briefly, hamsters were treated with AAS or sesame-oil control during adolescence and then microinjected with retrograde tracer into the medial amygdala (MeA), lateral septum (LS), or bed nucleus of the stria terminalis (BNST). Brains were then processed for vesicular glutamate transporter 2 (VGLUT2) and exa...

Blockade of NMDA receptors 2A subunit in the dorsal striatum impairs the learning of a complex motor skill.

Behavioral Neuroscience — Mon, 22 Aug 2011 04:00:00 +0100

Accumulating evidence proposes that the striatum, known to control voluntary movement, may also play a role in learning and memory. Striatum learning is thought to require long-lasting reorganization of striatal circuits and changes in the strength of synaptic connections during the memorization of a complex motor task. Whether the ionotropic glutamate receptor N-methyl-D-aspartate (NMDAR) contributes to the molecular mechanisms of these memory processes is still unclear. The aim of the present study was to investigate the role of striatal NMDAR and its subunit composition during the learning of the accelerating rotarod task in mice. To this end, we injected directly into the dorsal striatum of mice, via chronically implanted cannula, the NMDAR channel blocker MK-801 as well as the NR2A an...

Impulsivity as a mediating mechanism between early-life adversity and addiction: Theoretical comment on Lovic et al. (2011).

Behavioral Neuroscience — Sun, 24 Jul 2011 23:00:00 +0100

Early-life adversity, impulsivity, and dopaminergic function have all been implicated in adult drug addiction. The article by Lovic, Keen, Fletcher, and Fleming in this issue further elucidates this relationship by demonstrating that early-life adversity can increase impulsivity and decrease behavioral flexibility in adulthood. Recent literature suggests that these results are likely due to structural and functional changes in regions such as the orbitofrontal cortex (OFC) and nucleus accumbens (NAc), as well as altered dopamine activity. Impulsivity and behavioral inflexibility can increase susceptibility to addiction, and in turn, chronic substance abuse can impair the neurocircuitry underlying behavioral inhibition. Thus, early-life adversity may act as an entry point into a feed-forwar...

Rat behavior in go/no-go and two-alternative choice odor discrimination: Differences and similarities.

Behavioral Neuroscience — Sun, 24 Jul 2011 23:00:00 +0100

To elucidate the cognitive structures of animals, neuroscientists use several behavioral tasks. Therefore, it is imperative to have a firm understanding of each task's behavioral parameters in order to parse out possible task effects. We compare two operant discrimination tasks (Go/No-Go: GNG; Two-Alternative Choice: TAC) that are commonly used in olfactory research. Past research has suggested that solving the two tasks requires divergent cognitive strategies. One hypothesis is that the two tasks differ in how an animal optimizes reward rate by means of a speed–accuracy trade-off (SAT). If this is true, then changing tasks could give researchers an additional tool to understand animal cognition. However, no study has systematically analyzed the two tasks in parallel using odor stimuli. ...

Social regulation of serotonin in the auditory midbrain.

Behavioral Neuroscience — Sun, 24 Jul 2011 23:00:00 +0100

The neuromodulator serotonin regulates auditory processing and can increase within minutes in response to stimuli like broadband noise as well as nonauditory stressors. Little is known about the serotonergic response in the auditory system to more natural stimuli such as social interactions. Using carbon-fiber voltammetry, we measured extracellular serotonin in the auditory midbrain of resident male mice during encounters with a male intruder. Serotonin increased in the inferior colliculus (IC) over the course of a 15 minute interaction, but not when mice were separated with a perforated barrier. Several behaviors, including the amount of immobility and anogenital investigation performed by the resident, were correlated with the serotonergic response. Multiple intrinsic factors associated ...

Music-induced context preference following cocaine conditioning in rats.

Behavioral Neuroscience — Sun, 19 Jun 2011 23:00:00 +0100

Traditional models of drug-seeking behavior have shown that exposure to associated environmental cues can trigger relapse. These learned associations take place during repeated drug administration, resulting in conditioned reinforcement. Although considerable investigation has occurred regarding simple conditioned stimuli, less is known about complex environmental cues, particularly those that may be salient in human addiction. Recent studies indicate that music can serve as a contextual conditioned stimulus in rats and influence drug-seeking behavior during abstinence. The purpose of the present study was to further assess the effectiveness of music as a conditioned stimulus in rats, to determine rats' preferences for two contrasting pieces of music, and to determine rats' preferences for...

Genitosensory nerve modulation of paced mating behavior: Evidence for pelvic, but not hypogastric, nerve influence.

Behavioral Neuroscience — Sun, 19 Jun 2011 23:00:00 +0100

The pelvic nerve is known to play a role in the behavioral and neurochemical responses exhibited during paced mating behavior. The present study extended the analysis of the contribution of the genitosensory nerves to the display of paced mating behavior to include bilateral hypogastric nerve transection, bilateral pelvic nerve transection, or transection of both the hypogastric and pelvic nerves. Rats with pelvic nerve transection were less likely to exit the male compartment, took longer to exit the male compartment following intromissions, and returned to the male more quickly following intromissions compared to rats with an intact pelvic nerve. In contrast, hypogastric nerve transection alone did not affect paced mating and had no modulating effect on the paced mating behavior of rats ...

Videos of conspecifics elicit interactive looking patterns and facial expressions in monkeys.

Behavioral Neuroscience — Sun, 19 Jun 2011 23:00:00 +0100

A broader understanding of the neural basis of social behavior in primates requires the use of species-specific stimuli that elicit spontaneous, but reproducible and tractable behaviors. In this context of natural behaviors, individual variation can further inform about the factors that influence social interactions. To approximate natural social interactions similar to those documented by field studies, we used unedited video footage to induce in viewer monkeys spontaneous facial expressions and looking patterns in the laboratory setting. Three adult male monkeys (Macaca mulatta), previously behaviorally and genetically (5-HTTLPR) characterized, were monitored while they watched 10 s video segments depicting unfamiliar monkeys (movie monkeys) displaying affiliative, neutral, and aggressiv...

Systemic mifepristone blocks reconsolidation of cue-conditioned fear; Propranolol prevents this effect.

Behavioral Neuroscience — Sun, 19 Jun 2011 23:00:00 +0100

Reducing reconsolidation of reactivated traumatic memories may offer a novel pharmacological treatment for posttraumatic stress disorder (PTSD). Preclinical research is needed to identify candidate drugs. We evaluated the ability of postreactivation mifepristone (RU38486, a glucocorticoid antagonist), alone and in combination with propranolol (a beta-adrenergic blocker), both given systemically, to reduce cue-conditioned fear in rats. On Day 1, a 30-s tone conditioned stimulus (CS) was paired with an electric shock unconditioned stimulus (US). On Day 2, the CS was presented without the US (reactivation), and the freezing conditioned response (CR) was measured. This was immediately followed by subcutaneous injection of vehicle, mifepristone 30 mg/kg, propranolol 10 mg/kg, or both. On Day 3,...

Conditioned diminution of the unconditioned skin conductance response.

Behavioral Neuroscience — Sun, 19 Jun 2011 23:00:00 +0100

During Pavlovian conditioning the expression of a conditioned response typically serves as evidence that an association between a conditioned stimulus (CS) and an unconditioned stimulus (UCS) has been learned. However, learning-related changes in the unconditioned response (UCR) produced by a predictable UCS can also develop. In the present study, we investigated learning-related reductions in the magnitude of the unconditioned skin conductance response (SCR). Healthy volunteers participated in a differential conditioning study in which one tone (CS+) was paired with a loud white-noise UCS and a second tone (CS−) was presented alone. In addition, probe trials that consisted of UCS presentations paired with the CS+ (CS + UCS) and CS− (CS − UCS), as well as presentations of the UCS alo...

Classical conditioning and conditioning-specific reflex modification of rabbit heart rate as a function of unconditioned stimulus location.

Behavioral Neuroscience — Sun, 19 Jun 2011 23:00:00 +0100

Heart rate conditioning is used as an index of conditioned fear and is important for understanding disorders of anxiety and stress, including post traumatic stress disorder (PTSD). One important feature of PTSD is that patients generalize conditioned fear from danger signals to safety signals especially when the two signals have overlapping features. What has not been determined is whether generalization occurs between unconditioned stimuli with overlapping features. In the current experiment, heart rate conditioning and conditioning-specific reflex modification of rabbit heart rate were examined as a function of two different unconditioned stimulus locations. Heart rate conditioning occurred at identical terminal levels whether electrical stimulation was presented near the eye or on the b...

Involvement of retrosplenial cortex in forming associations between multiple sensory stimuli.

Behavioral Neuroscience — Sun, 19 Jun 2011 23:00:00 +0100

The retrosplenial cortex (RSP) is highly interconnected with medial temporal lobe structures, yet relatively little is known about its specific contributions to learning and memory. One possibility is that RSP is involved in forming associations between multiple sensory stimuli. Indeed, damage to RSP disrupts learning about spatial or contextual cues and also impairs learning about co-occurring conditioned stimuli (CSs). Two experiments were conducted to test this notion more rigorously. In Experiment 1, rats were trained in a serial feature negative discrimination task consisting of reinforced presentations of a tone alone and nonreinforced serial presentations of a light followed by the tone. Thus, in contrast to prior studies, this paradigm involved serial presentation of conditioned st...

Tap withdrawal circuit interneurons require CREB for long-term habituation in Caenorhabditis elegans.

Behavioral Neuroscience — Sun, 19 Jun 2011 23:00:00 +0100

We investigated the role of the Caenorhabditis elegans CREB (cAMP response element binding protein) homologue, crh-1, in response to tap (nonlocalized mechanosensory stimulation) and tap habituation. Worms with a loss-of-function mutation in crh-1 performed smaller reversals in response to tap than did wild-type worms and did not show long-term memory for spaced training 24-hr posttraining; however, they did show short-term habituation to tap stimuli when stimuli were presented at both 10-s and 60-s interstimulus intervals, and showed 12-hr intermediate memory for spaced habituation training (intermediate-term memory). Expressing CRH-1 broadly throughout the nervous system and in a subset of interneurons of the tap withdrawal circuit, but not in the mechanosensory neurons, rescued the long...

Effects of D-cycloserine on the extinction of appetitive operant learning.

Behavioral Neuroscience — Sun, 19 Jun 2011 23:00:00 +0100

Four experiments with rat subjects examined whether D-cycloserine (DCS), a partial NMDA agonist, facilitates the extinction of operant lever-pressing reinforced by food. Previous research has demonstrated that DCS facilitates extinction learning with methods that involve Pavlovian extinction. In the current experiments, operant conditioning occurred in Context A, extinction in Context B, and then testing occurred in both the extinction and conditioning contexts. Experiments 1A and 1B tested the effects of three doses of DCS (5, 15, and 30 mg/kg) on the extinction of lever pressing trained as a free operant. Experiment 2 examined their effects when extinction of the free operant was conducted in the presence of nonresponse-contingent deliveries of the reinforcer (that theoretically reduced ...

Inactivation of the median raphe nucleus increases intake of sucrose solutions: A microstructural analysis.

Behavioral Neuroscience — Sun, 19 Jun 2011 23:00:00 +0100

Previous studies have shown that microinjections of the GABA-A agonist muscimol into the median raphe nucleus (MR) result in large increases in the intake of solid foods. In the current study, we used microstructural techniques to characterize the effects of intra-MR muscimol injections on the consumption of either a 0.05 M or a 0.29 M sucrose solution. After injections of either saline or muscimol, animals consumed more of the 0.29 M than the 0.05 M solution, an effect which resulted primarily from increases in the initial rate of consumption with no change in the rate at which licking decayed across the test session. In contrast, intra-MR muscimol injections had little effect on the initial licking rate, but greatly increased meal duration, indicating that this treatment affected ingesti...

Fat substitutes promote weight gain in rats consuming high-fat diets.

Behavioral Neuroscience — Sun, 19 Jun 2011 23:00:00 +0100

The use of food products designed to mimic the sensory properties of sweet and fat while providing fewer calories has been promoted as a method for reducing food intake and body weight. However, such products may interfere with a learned relationship between the sensory properties of food and the caloric consequences of consuming those foods. In the present experiment, we examined whether use of the fat substitute, olestra, affect energy balance by comparing the effects of consuming high-fat, high-calorie potato chips to the effects of consuming potato chips that sometimes signaled high calories (using high-fat potato chips) and that sometimes signaled lower calories (using nonfat potato chips manufactured with the fat substitute olestra). Food intake, body weight gain and adiposity were g...

Early-life maternal separation and social isolation produce an increase in impulsive action but not impulsive choice.

Behavioral Neuroscience — Sun, 19 Jun 2011 23:00:00 +0100

Early life environment, events, and context, such as mother–offspring relationship, can have profound effects on future behavior and physiology. We investigated the effects of long-term maternal and social separation, through artificial rearing, on adult impulsivity. Rats were maternally reared (MR) or artificially reared (AR) and half of the AR rats were provided with replacement somatosensory stimulation intended to simulate maternal licking. There are at least 2 forms of impulsivity and we compared rats on 1 test of impulsive action (differential reinforcement of low rates of responding—DRL-20s) and 2 tests of impulsive choice (delay discounting and fixed consecutive number schedule—FCN). We found that AR rats are more action impulsive; however, this effect can be reduced by mater...

The role of context in re-acquisition of extinguished alcoholic beer-seeking.

Behavioral Neuroscience — Sun, 29 May 2011 23:00:00 +0100

We studied the role of context in reacquisition of extinguished reward-seeking. Rats were trained to respond for alcoholic beer, then extinguished and retrained. Reacquisition was faster than acquisition regardless of whether retraining occurred in the original training context, the extinction context, a novel context, or a context with a mixed history of reinforcement. Reacquisition was also rapid after extended extinction training. Nonetheless, context did significantly influence reacquisition via affecting latency to first response: rats took significantly longer to initiate responding when tested in the extinction context. These results suggest that reacquisition of drug and reward seeking is determined by an inhibitory influence caused by the extinction context and a facilitatory infl...

Orbitofrontal cortex and basolateral amygdala lesions result in suboptimal and dissociable reward choices on cue-guided effort in rats.

Behavioral Neuroscience — Sun, 29 May 2011 23:00:00 +0100

The orbitofrontal cortex (OFC) and basolateral nucleus of the amygdala (BLA) are important neural regions in responding adaptively to changes in the incentive value of reward. Recent evidence suggests these structures may be differentially engaged in effort and cue-guided choice behavior. In 2 T-maze experiments, we examined the effects of bilateral lesions of either BLA or OFC on (1) effortful choices in which rats could climb a barrier for a high reward or select a low reward with no effort and (2) effortful choices when a visual cue signaled changes in reward magnitude. In both experiments, BLA rats displayed transient work aversion, choosing the effortless low reward option. OFC rats were work averse only in the no cue conditions, displaying a pattern of attenuated recovery from the cu...

Animal models of prefrontal-executive function.

Behavioral Neuroscience — Sun, 29 May 2011 23:00:00 +0100

Executive function allows us to interact with the world in a purposive, goal-directed manner. It relies on several cognitive control operations that are mediated by different regions of the prefrontal cortex. While much of our knowledge about the functional subdivisions of the prefrontal cortex comes from the systematic assessment of patients with brain damage, animal models have served as the predominant tool for investigating specific structure–function relationships within the prefrontal cortex, especially as they relate to complex executive behaviors. These studies generally involve the targeted disruption of neural circuits combined with behavioral testing using carefully designed cognitive paradigms. In this review, I will describe a broad range of such experiments conducted in rat...

Introduction to the special section on “translational models of prefrontal cortical function”.

Behavioral Neuroscience — Sun, 29 May 2011 23:00:00 +0100

Impaired functioning of the prefrontal cortex is particularly prominent in many forms of psychopathology and in degenerative brain diseases. Because it is challenging to draw causal links between specific brain abnormalities and impaired cognition in these conditions, research using nonhuman animals has a key role to play in elucidating the neurobiological mechanisms of prefrontal cortex function and aiding the search for treatments. This role is clearly illustrated in the review articles and original research reports in this special section. Taken together, these papers demonstrate the insights that have already been gained from research with nonhuman animals as well as the work that still needs to be done to attain the goal of understanding human prefrontal cortical function in both heal...

Glossopharyngeal nerve transection impairs unconditioned avoidance of diverse bitter stimuli in rats.

Behavioral Neuroscience — Sun, 22 May 2011 23:00:00 +0100

There is growing evidence of heterogeneity among responses to bitter stimuli at the peripheral, central and behavioral levels. For instance, the glossopharyngeal (GL) nerve and neurons receiving its projections are more responsive to bitter stimuli than the chorda tympani (CT) nerve, and this is particularly true for some bitter stimuli like PROP & cycloheximide that stimulate the GL to a far greater extent. Given this information, we hypothesized that cutting the GL would have a greater effect on behavioral avoidance of cycloheximide and PROP than quinine and denatonium, which also stimulate the CT, albeit to a lesser degree than salts and acids. Forty male SD rats were divided into four surgery groups: bilateral GL transection (GLX), chorda tympani transection (CTX), SHAM surgery, and co...

The risky business of dopamine agonists in Parkinson disease and impulse control disorders.

Behavioral Neuroscience — Sun, 22 May 2011 23:00:00 +0100

Risk-taking behavior is characterized by pursuit of reward in spite of potential negative consequences. Dopamine neurotransmission along the mesocorticolimbic pathway is a potential modulator of risk behavior. In patients with Parkinson's disease (PD), impulse control disorder (ICD) can result from dopaminergic medication use, particularly dopamine agonists (DAA). Behaviors associated with ICD include hypersexuality as well as compulsive gambling, shopping, and eating, and these behaviors are potentially linked to alterations to risk processing. Using the Balloon Analogue Risk Task, we assessed the role of agonist therapy on risk-taking behavior in PD patients with (n = 22) and without (n = 19) active ICD symptoms. Patients performed the task both “on” and “off” DAA. DAA increased ...

Pattern memory involves both elemental and configural processes: Evidence from the effects of hippocampal lesions.

Behavioral Neuroscience — Sun, 15 May 2011 23:00:00 +0100

The formation of an integrated memory for a pattern of stimulation could be based on the elements of that pattern becoming directly linked to one another, or by each of the elements becoming linked to a shared separate configural representation. These 2 accounts have proven difficult to discriminate between. Here, rats received exposure to four patterns of stimulation, each consisting of an auditory stimulus, a visual context, and a time of day; and we examined whether pre-training lesions to the hippocampus influenced memory for the patterns. These lesions abolished pattern memory that required configural processes (Experiments 1A and 1B) but had no effect on pattern memory that could be supported by elemental processes (Experiment 2). This dissociation provides support for the views that...

Amphetamine-induced incentive sensitization of sign-tracking behavior in adolescent and adult female rats.

Behavioral Neuroscience — Sun, 01 May 2011 23:00:00 +0100

Age-specific behavioral and neural characteristics may predispose adolescents to initiate and escalate use of alcohol and drugs. Adolescents may avidly seek novel experiences, including drugs of abuse, because of enhanced incentive motivation for drugs and natural rewards, perhaps especially when that incentive motivation is sensitized by prior drug exposure. Using a Pavlovian conditioned approach (PCA) procedure, sign-tracking (ST) and goal-tracking (GT) behavior was examined in amphetamine-sensitized and control adolescent and adult female Sprague–Dawley rats, with expression of elevated ST behavior used to index enhanced incentive motivation for reward-associated cues. Rats were first exposed to a sensitizing regimen of amphetamine injections (3.0 mg/kg/ml d-amphetamine per day) or gi...

Right-handedness predominance in 162 baboons (Papio anubis) for gestural communication: Consistency across time and groups.

Behavioral Neuroscience — Sun, 01 May 2011 23:00:00 +0100

Whether nonhuman primates exhibit population level right manual bias remains a controversial topic. In captive baboons, population-level right-handedness has been reported for both coordinated bimanual actions and communicative gestures. However, some authors remain skeptical of these findings on both methodological and theoretical grounds. Here, we demonstrated the robustness and the consistency across time of the pattern of right-handedness for a species-specific communicative gesture in olive baboons (Papio anubis). First, we showed significant correlations in the 26 retested baboons for the measures of hand preferences between the first and the second session conducted 4 years later (2005–2009) by an observer blind to the previous handedness data. Second, the replication of the study...

Decision making and reward in frontal cortex: Complementary evidence from neurophysiological and neuropsychological studies.

Behavioral Neuroscience — Sun, 01 May 2011 23:00:00 +0100

Patients with damage to the prefrontal cortex (PFC)—especially the ventral and medial parts of PFC—often show a marked inability to make choices that meet their needs and goals. These decision-making impairments often reflect both a deficit in learning concerning the consequences of a choice, as well as deficits in the ability to adapt future choices based on experienced value of the current choice. Thus, areas of PFC must support some value computations that are necessary for optimal choice. However, recent frameworks of decision making have highlighted that optimal and adaptive decision making does not simply rest on a single computation, but a number of different value computations may be necessary. Using this framework as a guide, we summarize evidence from both lesion studies and ...

Spontaneous recovery but not reinstatement of the extinguished conditioned eyeblink response in the rat.

Behavioral Neuroscience — Sun, 24 Apr 2011 23:00:00 +0100

Reinstatement—the return of an extinguished conditioned response (CR) after reexposure to the unconditioned stimulus (US)—and spontaneous recovery—the return of an extinguished CR with the passage of time—are 2 of 4 well-established phenomena that demonstrate that extinction does not erase the conditioned stimulus (CS)–US association. However, reinstatement of extinguished eyeblink CRs has never been demonstrated, and spontaneous recovery of extinguished eyeblink CRs has not been systematically demonstrated in rodent eyeblink conditioning. In Experiment 1, US reexposure was administered 24 hr prior to a reinstatement test. In Experiment 2, US reexposure was administered 5 min prior to a reinstatement test. In Experiment 3, a long, discrete cue (a houselight), present in all phase...

Discrimination learning and attentional set formation in a mouse model of Fragile X.

Behavioral Neuroscience — Sun, 24 Apr 2011 23:00:00 +0100

Fragile X Syndrome is the most prevalent genetic cause of mental retardation. Selective deficits in executive function, including inhibitory control and attention, are core features of the disorder. In humans, Fragile X results from a trinucleotide repeat in the Fmr1 gene that renders it functionally silent and has been modeled in mice by targeted deletion of the Fmr1 gene. Fmr1 knockout (KO) mice recapitulate many features of Fragile X syndrome, but evidence for deficits in executive function is inconsistent. To address this issue, we trained wild-type and Fmr1 KO mice on an experimental paradigm that assesses attentional set-shifting. Mice learned to discriminate between stimuli differing in two of three perceptual dimensions. Successful discrimination required attending only to the rele...

ROCK inhibition prevents tau hyperphosphorylation and p25/CDK5 increase after global cerebral ischemia.

Behavioral Neuroscience — Sun, 24 Apr 2011 23:00:00 +0100

Rho-kinase (ROCK) is a downstream effector of RhoA, which has been associated with growth cone collapse and retraction in neurons. ROCK inhibition has been shown to protect against ischemic damage, thereby improving short-term collateral flow, inhibiting platelet aggregation, leukocyte adhesion, and preventing neuronal death. However, little is known about the long-term effects of ROCK inhibition on behavior and neuroprotection. The consequence of ROCK inhibition on ischemic rats' learning and spatial memory after 30 days of intracerebroventricular treatment was evaluated. It was found that Y27632 (ROCK inhibitor) reduced neurodegenerative markers, such as Fluoro-Jade, PHF (paired helicoidal filaments) immunoreactivity, and p25 protein levels, in the hippocampus of ischemic animals and imp...

Coexpression of sexual behavior and maternal aggression: The ambivalence of sexually active mother rats toward male intruders.

Behavioral Neuroscience — Sun, 24 Apr 2011 23:00:00 +0100

This study shows that postpartum estrous females exhibit a merge of sexual and maternal aggressive responses toward male intruders in the home cage. The concurrent expression of these behaviors did not affect their intensities, although the stimulation of maternal behavior increased maternal aggression without modifying sexual solicitation. These results indicate that the postpartum estrous rat can optimally express two opposite and independently regulated motivations, and that the male can be perceived as an ambivalent stimulus. (PsycINFO Database Record (c) 2011 APA, all rights reserved) (Source: Behavioral Neuroscience)

Impaired eyeblink conditioning in 78kDa-glucose regulated protein (GRP78)/immunoglobulin binding protein (BiP) conditional knockout mice.

Behavioral Neuroscience — Sun, 24 Apr 2011 23:00:00 +0100

Evidence grows that the cerebellum and its associated circuitry are the essential neural substrates for standard delay classical eyeblink conditioning. To further investigate the relative roles of the cerebellar cortex and nuclei in eyeblink conditioning, a novel mouse model with Purkinje cell atrophy was studied. The 78kDa-glucose regulated protein, a chaperone molecule, was knocked out leading to postnatal Purkinje cell degeneration (Wang et al., 2010), and standard delay eyeblink conditioning was performed in the conditional knockout mice. Learning was impaired, yet not completely prevented. Histological studies showed a reduction in the cell number and the size of the anterior interpositus nucleus. When the anterior interpositus nucleus was lesioned bilaterally, eyeblink conditioning w...

Dissociations between medial prefrontal cortical subregions in the modulation of learning and action.

Behavioral Neuroscience — Sun, 24 Apr 2011 23:00:00 +0100

The medial prefrontal cortex (mPFC) has been implicated in various attentional functions. This experiment examined the involvement of mPFC subregions in the allocation of attention in learning and action as a function of the predictive accuracy of cues. Rats with dorsal (encompassing anterior cingulate, prelimbic, and infralimbic cortices) or ventral (encompassing mainly infralimbic and dorsopeduncular cortices and tenia tecta) mPFC lesions were trained in a multiple-choice discrimination task in which operant nosepoke responses to some visual cues were consistently (100%) reinforced (CRF) with food, whereas responses to other visual cues were partially (50%) reinforced (PRF). In challenge tests designed to assess attention in the control of action, responding was directed more to CRF cues...

Exploring prefrontal cortical memory mechanisms with eyeblink conditioning.

Behavioral Neuroscience — Sun, 24 Apr 2011 23:00:00 +0100

Several studies in nonhuman primates have shown that neurons in the dorsolateral prefrontal cortex have activity that persists throughout the delay period in delayed matching to sample tasks, and age-related changes in the microcolumnar organization of the prefrontal cortex are significantly correlated with age-related declines in cognition. Activity that persists beyond the presentation of a stimulus could mediate working memory processes, and disruption of those processes could account for memory deficits that often accompany the aging process. These potential memory and aging mechanisms are being systematically examined with eyeblink conditioning paradigms in nonprimate mammalian animal models including the rabbit. The trace version of the conditioning paradigm is a particularly good sy...

Developmental and withdrawal effects of adolescent AAS exposure on the glutamatergic system in hamsters.

Behavioral Neuroscience — Sun, 17 Apr 2011 23:00:00 +0100

In the Syrian hamster (Mesocricetus auratus) glutamate activity has been implicated in the modulation of adolescent anabolic-androgenic steroid (AAS)-induced aggression. The current study investigated the time course of adolescent AAS-induced neurodevelopmental and withdrawal effects on the glutamatergic system and examined whether these changes paralleled those of adolescent AAS-induced aggression. Glutamate activity in brain areas comprising the aggression circuit in hamsters and aggression levels were examined following 1, 2, 3, and 4 weeks of AAS treatment or 1, 2, 3, and 4 weeks following the cessation of AAS exposure. In these studies glutamate activity was examined using vesicular glutamate transporter 2 (VGLUT2). The onset of aggression was observed following 2 weeks exposure to AA...

Proinflammatory activity and the sensitization of depressive-like behavior during maternal separation.

Behavioral Neuroscience — Sun, 17 Apr 2011 23:00:00 +0100

When guinea pig pups are isolated for a few hours in a novel environment, they exhibit a distinctive passive behavioral response that appears to be mediated by proinflammatory activity. Recently, we observed that pups separated on two consecutive days show an enhanced (sensitized) passive response on the second day. In Experiment 1, pups receiving intracerebroventricular infusion of 50 ng of the anti-inflammatory cytokine interleukin-10 prior to a first separation failed to show a sensitized behavioral response to separation the next day. In Experiment 2, pups separated on Days 1 and 2, or just 2, showed an increase in passive responding during separation on Day 5. Pups injected with the bacterial antigen lipopolysacchride (LPS; 75 μg/kg body weight, intraperitoneal) prior to separation o...

Set shifting in a rodent model of attention-deficit/hyperactivity disorder.

Behavioral Neuroscience — Sun, 17 Apr 2011 23:00:00 +0100

Two experiments compared spontaneously hypertensive rats (SHRs; a rodent model of attention-deficit/hyperactivity disorder) and Wistar rats (a normoactive control strain), on the acquisition of a set-shifting strategy. In Experiment 1, SHRs and Wistar rats were equivalent in trials to criterion to learn a brightness or a texture discrimination but SHRs were faster than Wistar rats in shifting to the opposite discrimination when there was 1 or 2 days between the initial discrimination and the shift. In Experiment 2, SHRs and Wistar rats were equivalent in shifting when the shift between discriminations occurred immediately after a criterion had been met in the first discrimination. The results are discussed in terms of a failure of SHRs to store or retrieve an initial discrimination and/or ...

Rat prefrontal dopamine and cognitive control: Impaired and enhanced conflict performance.

Behavioral Neuroscience — Sun, 17 Apr 2011 23:00:00 +0100

It has been proposed that the cognitive dysfunction observed in patients with schizophrenia reflects a failure in cognitive control, in particular an inability to use task-relevant information to guide behavior. Using a prefrontal-dependent task designed to reflect aspects of cue and response conflict seen in human cognitive paradigms, we examined the influence of prefrontal dopamine receptor manipulation on the contextual control of response conflict. Rats were trained on two biconditional discrimination tasks, one auditory and one visual, in two discriminably different contexts. At test, audiovisual compounds of these training stimuli were presented, in extinction, in each of the training contexts. These compounds were formed in such a way that the individual elements previously dictated...

Maternal defense is modulated by beta adrenergic receptors in lateral septum in mice.

Behavioral Neuroscience — Sun, 10 Apr 2011 23:00:00 +0100

In this study using a strain of mice selected for maternal defense, we examined whether possible changes in NE signaling in the lateral septum (LS) could facilitate expression of maternal aggression. In separate studies that utilized a repeated measures design, mice were tested for maternal defense following intra-LS injections of either the β-adrenergic receptor agonist isoproterenol (10 μg or 30 μg) or vehicle (Experiment 1), the β-adrenergic receptor antagonist propranolol (2 μg) or vehicle (Experiment 2), or the β1-receptor antagonist, atenolol (Experiment 3). Mice were also evaluated for light–dark performance and pup retrieval. Thirty micrograms of the agonist isoproterenol significantly decreased number of attacks and time aggressive relative to vehicle without affecting pup...

Outcome-specific satiety reveals a deficit in context-outcome, but not stimulus- or action-outcome, associations in aged Tg2576 mice.

Behavioral Neuroscience — Sun, 10 Apr 2011 23:00:00 +0100

The onset of Alzheimer's disease (AD) is often accompanied by changes in emotion, motivation, and goal-directed behavior. The production of beta-amyloid is thought to be a major and early contributor to the pathogenesis of AD. The present study tested the hypothesis that amyloid pathology present in the amygdala, frontal cortex, and hippocampus of Tg2576 mice would disrupt the development of instrumental- and/or Pavlovian-outcome associations. The results showed that both instrumental- and Pavlovian-conditioned behaviors were sensitive to outcome devaluation (Experiments 1 & 2) and that Pavlovian cues influenced goal-directed actions associated with the same outcome (Experiment 2) in Tg2576 mice. In contrast, context mediated Pavlovian-conditioned behaviors in aged (Experiment 3a) but not ...

The effect of catecholaminergic depletion within the prelimbic and infralimbic medial prefrontal cortex on recognition memory for recency, location, and objects.

Behavioral Neuroscience — Sun, 10 Apr 2011 23:00:00 +0100

There is good evidence that the medial prefrontal cortex (mPFC) is involved in different aspects of recognition memory. However, the mPFC is a heterogeneous structure, and the contribution of the prelimbic (PL) and infralimbic (IL) cortices to recognition memory has not been investigated. Similarly, the role of different neuromodulators within the mPFC in these processes is poorly understood. To this end, we tested animals with 6-hydroxydopamine (6-OHDA) lesions of the PL and IL mPFC on three tests of object recognition memory that required judgments about recency, object location, and object identity. In the recency task, lesions to both PL and IL severely impaired animals' ability to differentiate between old (earlier presented) and recently presented familiar objects. Relative to sham a...

Attentional effects of lesions to the anterior cingulate cortex: How prior reinforcement influences distractibility.

Behavioral Neuroscience — Sun, 10 Apr 2011 23:00:00 +0100

Morphological changes in the anterior cingulate cortex are found in subjects with schizophrenia, attention deficit hyperactivity disorder, and obsessive–compulsive disorder. These changes are hypothesized to underlie the impairments these individuals show on tasks that require cognitive control. The anterior cingulate cortex has previously been shown to be active in situations involving high conflict, presentation of salient, distracting stimuli, and error processing, that is, situations that occur when a shift in attention or responding is required. However, there is some uncertainty as to what specific role the anterior cingulate cortex plays in these situations. The current study used converging evidence from two behavioral paradigms to determine the effects of excitotoxic lesions in ...

Molecular modulation of prefrontal cortex: Rational development of treatments for psychiatric disorders.

Behavioral Neuroscience — Sun, 10 Apr 2011 23:00:00 +0100

Dysfunction of the prefrontal cortex (PFC) is a central feature of many psychiatric disorders, such as attention deficit hyperactivity disorder (ADHD), posttraumatic stress disorder (PTSD), schizophrenia, and bipolar disorder. Thus, understanding molecular influences on PFC function through basic research in animals is essential to rational drug development. In this review, we discuss the molecular signaling events initiated by norepinephrine and dopamine that strengthen working memory function mediated by the dorsolateral PFC under optimal conditions, and weaken working memory function during uncontrollable stress. We also discuss how these intracellular mechanisms can be compromised in psychiatric disorders, and how novel treatments based on these findings may restore a molecular environ...

The mu-opioid receptor and the evolution of mother-infant attachment: Theoretical comment on Higham et al. (2011).

Behavioral Neuroscience — Sun, 03 Apr 2011 23:00:00 +0100

Genetic variation at a single nucleotide polymorphism (SNP) in the mu-opioid receptor gene (OPRM1) of both humans and rhesus macaques Macaca mulatta has been associated with differential affinity to the endogenous ligand beta-endorphin as well as alterations in pain sensitivity, drug and alcohol dependence, and social behaviors. The new study by Higham et al. (2011) presented in the current issue of this journal shows for the first time that some of the natural variation in maternal behavior observed in rhesus macaque populations can also be explained by genetic differences at this SNP. This work, in conjunction with other recent studies showing that genetic variability at this same locus are related to changes in infant attachment, provides unique insights into how opioids have been reuti...

Clozapine and PD149163 elevate prepulse inhibition in Brown Norway rats.

Behavioral Neuroscience — Sun, 03 Apr 2011 23:00:00 +0100

Unmedicated schizophrenia patients exhibit deficits in prepulse inhibition (PPI) of the acoustic startle response. Similar deficits can be induced in rodents via a variety of manipulations and these deficits can be reversed by antipsychotics. Brown Norway (BN) rats exhibit natural PPI deficits under certain parametric conditions. We treated BN rats with haloperidol or clozapine to determine if the BN rat is a useful animal model with predictive validity for the effects of antipsychotics. In addition, we also tested PD149163, a neurotensin-1 receptor agonist, which has been shown to exhibit antipsychotic-like effects in several other animal models. BN rats received subcutaneous injections of either saline or one of two doses of haloperidol (0.5 mg/kg, 1.0 mg/kg), clozapine (7.5 mg/kg, 10 mg...

Baclofen facilitates the extinction of methamphetamine-induced conditioned place preference in rats.

Behavioral Neuroscience — Sun, 03 Apr 2011 23:00:00 +0100

The powerful, long-lasting association between the rewarding effects of a drug and contextual cues associated with drug administration can be studied using conditioned place preference (CPP). The GABAB receptor agonist baclofen facilitates the extinction of morphine-induced CPP in mice. The current study extended this work by determining if baclofen could enhance the extinction of methamphetamine (Meth) CPP. CPP was established using a six-day conditioning protocol wherein Meth-pairings were alternated with saline-pairings. Rats were subsequently administered baclofen (2 mg/kg i.p. or vehicle) immediately after each daily forced extinction session, which consisted of a saline injection immediately prior to being placed into the previously Meth- or saline-paired chamber. One extinction trai...

Effects of sleep inertia after daytime naps vary with executive load and time of day.

Behavioral Neuroscience — Sun, 03 Apr 2011 23:00:00 +0100

The effects of executive load on working memory performance during sleep inertia after morning or afternoon naps were assessed using a mixed design with nap/wake as a between-subjects factor and morning/afternoon condition as a within-subject factor. Thirty-two healthy adults (mean 22.5 ± 3.0 years) attended two laboratory sessions after a night of restricted sleep (6 hrs), and at first visit, were randomly assigned to the Nap or Wake group. Working memory (n-back) and subjective workload were assessed approximately 5 and 25 minutes after 90-minute morning and afternoon nap opportunities and at the corresponding times in the Wake condition. Actigraphically assessed nocturnal sleep duration, subjective sleepiness, and psychomotor vigilance performance before daytime assessments did not var...

Nucleus accumbens dopamine modulates response rate but not response timing in an interval timing task.

Behavioral Neuroscience — Sun, 03 Apr 2011 23:00:00 +0100

While previous work has demonstrated that systemic dopamine manipulations can modulate temporal perception by altering the speed of internal clock processes, the neural site of this modulation remains unclear. Based on recent research suggesting that changes in incentive salience can alter the perception of time, as well as work showing that nucleus accumbens (NAc) shell dopamine (DA) levels modulate the incentive salience of discriminative stimuli that predict instrumental outcomes, we assessed whether microinjections of DA agents into the NAc shell would impact temporal perception. Rats were trained on either a 10-s or 30-s temporal production procedure and received intra-NAc shell microinfusions of sulpiride, amphetamine, and saline. Results showed that NAc DA modulations had no effect ...

Delay discounting in C57BL/6J and DBA/2J mice: Adolescent-limited and life-persistent patterns of impulsivity.

Behavioral Neuroscience — Sun, 03 Apr 2011 23:00:00 +0100

Impulsivity is a defining characteristic of adolescence. Compared to adults, for example, adolescents engage in higher rates of drug and alcohol experimentation, risky sexual practices, and criminal activity. Such behavior may reflect reduced sensitivity to long-term consequences of behavior during adolescence. Recently, our lab has attempted to refine mouse procedures to study developmental trends in decision making in the laboratory. In the present experiment, we examined sensitivity to delayed rewards in C57BL/6J (B6) and DBA/2J (D2) mice during adolescence and adulthood using an adaptation of a 2-week delay discounting procedure developed by Adriani and Laviola (2003). During training, mice could choose between a 20- or 100-μl drop of milk delivered after a 1-s delay. During testing, ...

Pharmacobehavioural evidence for nitric oxide and noradrenaline interactions with ryanodine receptors during memory formation in the young chick.

Behavioral Neuroscience — Sun, 03 Apr 2011 23:00:00 +0100

Tactile stimulation during development attenuates amphetamine sensitization and structurally reorganizes prefrontal cortex and striatum in a sex-dependent manner.

Behavioral Neuroscience — Sun, 03 Apr 2011 23:00:00 +0100

This study investigated the effect of postnatal tactile stimulation (TS) on juvenile behavior, adult amphetamine (AMPH) sensitization, and the interaction of TS and AMPH on prefrontal cortical (PFC) thickness and striatum size. Pups received TS by stroking daily with a feather duster from birth till weaning and were tested, as juveniles, in behavioral tasks including open field locomotion, elevated maze, novel object recognition, and play fighting behavior. Development and persistence of drug-induced behavioral sensitization was tested by chronic AMPH administration and challenge, respectively. PFC thickness and striatum size were assessed from serial brain sections. The findings showed that TS rats spent less time with novel objects on first exposure but open field locomotion and elevated...

Early adversity and serotonin transporter genotype interact with hippocampal glucocorticoid receptor mRNA expression, corticosterone, and behavior in adult male rats.

Behavioral Neuroscience — Sun, 03 Apr 2011 23:00:00 +0100

We examined the interaction between serotonin transporter (5-HTT) genotype, prenatal and postnatal stress on glucocorticoid receptor (GR) mRNA expression, corticosteroid stress responses, and behavior in adult male rats. Prenatal stress involved a daily restraint of pregnant dams from gestational Day 10–21. Postnatal stress involved raising pups after parturition either by their mothers (MR) or in the artificial rearing (AR) paradigm, with or without additional “licking-like” stroking stimulation. 5-HTT genotype, hippocampal GR mRNA level, corticosteroid stress response, and behaviors including startle response, prepulse inhibition (PPI), and locomotor activity were measured in adult male rat offspring. We found significant genotype by prenatal stress interactions for hippocampal GR ...

Mu-opioid receptor (OPRM1) variation, oxytocin levels and maternal attachment in free-ranging rhesus macaques Macaca mulatta.

Behavioral Neuroscience — Sun, 03 Apr 2011 23:00:00 +0100

Understanding the genetic and neuroendocrine basis of the mother-infant bond is critical to understanding mammalian affiliation and attachment. Functionally similar nonsynonymous mu-opioid receptor (OPRM1) SNPs have arisen and been maintained in humans (A118G) and rhesus macaques Macaca mulatta (C77G). In rhesus macaques, variation in OPRM1 predicts individual differences in infant affiliation for mothers. Specifically, infants carrying the G allele show increased distress on separation from their mothers, and spend more time with them upon reunion, than individuals homozygous for the C allele. In humans, individuals possessing the G allele report higher perceptions of emotional pain on receiving rejection by social partners. We studied maternal behavior over the course of a year among fre...

Fos expression in the prefrontal cortex and nucleus accumbens following exposure to retrospective timing tasks.

Behavioral Neuroscience — Mon, 21 Feb 2011 00:00:00 +0100

We examined whether performance of temporal discrimination tasks is associated with increased neuronal activation in these areas, as revealed by Fos expression, a marker for neuronal activation. In Experiment 1, rats were trained on a discrete-trials temporal discrimination task in which a light (22 cd/m²) was presented for a variable time, t (2.5–47.5 s), after which levers A and B were presented. A response on lever A was reinforced if t t > 25 s. A second group was trained on a light-intensity discrimination procedure, in which a light of variable intensity, i (3.6–128.5 cd/m²) was presented for 25 s. A response on lever A was reinforced if i i > 22 cd/m². In Experiment 2, bisection procedures were used to assess temporal (200–800 ms, 22 cd/m²) and light-intensity (3.6–128.5...

Effects of selective neonatal hippocampal lesions on tests of object and spatial recognition memory in monkeys.

Behavioral Neuroscience — Mon, 21 Feb 2011 00:00:00 +0100

Earlier studies in monkeys have reported mild impairment in recognition memory after nonselective neonatal hippocampal lesions. To assess whether the memory impairment could have resulted from damage to cortical areas adjacent to the hippocampus, we tested adult monkeys with neonatal focal hippocampal lesions and sham-operated controls in three recognition tasks: delayed nonmatching-to-sample, object memory span, and spatial memory span. Further, to rule out that normal performance on these tasks may relate to functional sparing following neonatal hippocampal lesions, we tested adult monkeys that had received the same focal hippocampal lesions in adulthood and their controls in the same three memory tasks. Both early and late onset focal hippocampal damage did not alter performance on any ...

Synthetic versus natural cat odorant effects on rodent behavior and medial amygdala plasticity.