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Wavelet Analysis as a Tool for Investigating Movement-Related Cortical Oscillations in EEG-fMRI Coregistration.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study we used EEG-fMRI to determine the possible correlation between topographical movement-related EEG changes in brain oscillatory activity recorded from EEG electrodes over the scalp and fMRI cortical responses in motor areas during finger movement. Thirty-two channels of EEG were recorded in 12 subjects during eyes-closed condition inside a three T magnetic resonance (MR) scanner using an MR-compatible EEG recording system. Off-line MRI artifact subtraction software was applied to obtain continuous EEG data during fMRI acquisition. For EEG data analysis we used a time-frequency approach to measure time by varyi...
Source: Brain Topography - November 18, 2009 Category: Neuroscience Authors: Storti SF, Formaggio E, Beltramello A, Fiaschi A, Manganotti P Tags: Brain Topogr Source Type: journals

Prospects for Clinical Applications of Transcranial Magnetic Stimulation and Real-Time EEG in Epilepsy.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Recent advances in methods for transcranial magnetic stimulation (TMS) enable its coupling to real-time EEG (TMS-EEG). Although TMS-EEG is applied largely in neurophysiology research, there are prospects for its use in clinical TMS practice, particularly in epilepsy where EEG is already in wide use, and where TMS is emerging as a diagnostic and therapeutic tool. In diagnostic applications, TMS-EEG may provide a useful measure of cortical excitability at baseline or after antiepileptic treatment. For therapeutic purposes, TMS-EEG may be of use in selection of appropriate TMS strength outside of the motor cortex where th...
Source: Brain Topography - November 17, 2009 Category: Neuroscience Authors: Rotenberg A Tags: Brain Topogr Source Type: journals

Using EEG to Explore How rTMS Produces Its Effects on Behavior.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A commonly held view is that, when delivered during the performance of a task, repetitive TMS (rTMS) influences behavior by producing transient "virtual lesions" in targeted tissue. However, findings of rTMS-related improvements in performance are difficult to reconcile with this assumption. With regard to the mechanism whereby rTMS influences concurrent task performance, a combined rTMS/EEG study conducted in our lab has revealed a complex set of relations between rTMS, EEG activity, and behavioral performance, with the effects of rTMS on power in the alpha band and on alpha:gamma phase synchrony each predicting its e...
Source: Brain Topography - November 14, 2009 Category: Neuroscience Authors: Johnson JS, Hamidi M, Postle BR Tags: Brain Topogr Source Type: journals

Thinning of the motor-cingulate-insular cortices in siblings concordant for tourette syndrome.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We report high relatedness/similarity estimates for fraternal siblings concordant for TS (r = 0.86-0.60) in the middle frontal-motor/cingulate/insular cortices. Regression analysis revealed significant negative correlations in the right insula with the YGTSS (r = -0.41, F = 6.09, P < 0.02) and the left cingulated cortex with the (CY-BOCS) (r = -0.35, F = 4.30, P < 0.05). Since previous findings have concluded that normal fraternal siblings are less alike in frontal cortices, the present findings may be attributed to TS. We speculate that the high ICC between siblings and the negative correlation between TS symptoms s...
Source: Brain Topography - September 27, 2009 Category: Neuroscience Authors: Fahim C, Yoon U, Sandor P, Frey K, Evans AC Tags: Brain Topogr Source Type: journals

Characteristic Changes in Brain Electrical Activity Due to Chronic Hypoxia in Patients with Obstructive Sleep Apnea Syndrome (OSAS): A Combined EEG Study Using LORETA and Omega Complexity.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
EEG background activity of patients with obstructive sleep apnea syndrome (OSAS, N = 25) was compared to that of normal controls (N = 14) to reflect alterations of brain electrical activity caused by chronic intermittent hypoxia in OSAS. Global and regional (left vs. right, anterior vs. posterior) measures of spatial complexity (Omega) were used to characterize the degree of spatial synchrony of EEG. Low resolution electromagnetic tomography (LORETA) was used to localize generators of EEG activity in separate frequency bands. Comparing patients to controls, lower Omega complexity was found globally and in the right hem...
Source: Brain Topography - August 26, 2009 Category: Neuroscience Authors: Toth M, Faludi B, Wackermann J, Czopf J, Kondakor I Tags: Brain Topogr Source Type: journals

Brain Cortical Mapping by Simultaneous Recording of Functional Near Infrared Spectroscopy and Electroencephalograms from the Whole Brain During Right Median Nerve Stimulation.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
To investigate relationships between hemodynamic responses and neural activities in the somatosensory cortices, hemodynamic responses by near infrared spectroscopy (NIRS) and electroencephalograms (EEGs) were recorded simultaneously while subjects received electrical stimulation in the right median nerve. The statistical significance of the hemodynamic responses was evaluated by a general linear model (GLM) with the boxcar design matrix convoluted with Gaussian function. The resulting NIRS and EEGs data were stereotaxically superimposed on the reconstructed brain of each subject. The NIRS data indicated that changes in...
Source: Brain Topography - August 24, 2009 Category: Neuroscience Authors: Takeuchi M, Hori E, Takamoto K, Tran AH, Satoru K, Ishikawa A, Ono T, Endo S, Nishijo H Tags: Brain Topogr Source Type: journals

Intracranial Recording and Source Localization of Auditory Brain Responses Elicited at the 50 ms Latency in Three Children Aged from 3 to 16 Years.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study provides results to support the notion that deviations in cognitive function(s) attributed to the auditory P50 in adults might involve abnormalities in neuronal activity of the frontal lobe or in the interaction between the frontal and temporal lobes. Validation and localisation of progenitors of the adults' P50 in young children is a much-needed step in the understanding of the biological significance of different subcomponents that comprise the auditory P50 in the adult brain. In combination with other approaches investigating neuronal mechanisms of auditory P50, the present results contribute to the greater u...
Source: Brain Topography - August 21, 2009 Category: Neuroscience Authors: Korzyukov O, Asano E, Gumenyuk V, Juhász C, Wagner M, Rothermel RD, Chugani HT Tags: Brain Topogr Source Type: journals

Meditators and Non-Meditators: EEG Source Imaging During Resting.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Many meditation exercises aim at increased awareness of ongoing experiences through sustained attention and at detachment, i.e., non-engaging observation of these ongoing experiences by the intent not to analyze, judge or expect anything. Long-term meditation practice is believed to generalize the ability of increased awareness and greater detachment into everyday life. We hypothesized that neuroplasticity effects of meditation (correlates of increased awareness and detachment) would be detectable in a no-task resting state. EEG recorded during resting was compared between Qigong meditators and controls. Using LORETA (...
Source: Brain Topography - August 3, 2009 Category: Neuroscience Authors: Tei S, Faber PL, Lehmann D, Tsujiuchi T, Kumano H, Pascual-Marqui RD, Gianotti LR, Kochi K Tags: Brain Topogr Source Type: journals

Steady State Visually Evoked Potential Correlates of Static and Dynamic Emotional Face Processing.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study examined the brain electrical activity changes in 26 participants (14 males M = 21.64, SD = 3.99; 12 females M = 24.42, SD = 4.36), during a passive face viewing task, a scrambled face task and separate emotion and gender face discrimination tasks. The steady state visual evoked potential (SSVEP) was recorded from 64-electrode sites. Consistent with previous research, face related activity was evidenced at scalp regions over the parieto-temporal region approximately 170 ms after stimulus presentation. Results also identified different SSVEP spatio-temporal changes associated with the processing of static and dyn...
Source: Brain Topography - August 3, 2009 Category: Neuroscience Authors: Mayes AK, Pipingas A, Silberstein RB, Johnston P Tags: Brain Topogr Source Type: journals

Similarities Between Simulated Spatial Spectra of Scalp EEG, MEG and Structural MRI.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Electrical dipoles oriented perpendicular to the cortical surface are the primary source of the scalp EEGs and MEGs. Thus, in particular, gyri and sulci structures on the cortical surface have a definite possibility to influence the EEGs and MEGs. This was examined by comparing the spatial power spectral density (PSD) of the upper portion of the human cortex in MRI slices to that of simulated scalp EEGs and MEGs. The electrical activity was modeled with 2,650 dipolar sources oriented normal to the local cortical surface. The resulting scalp potentials were calculated with a finite element model of the head constructed ...
Source: Brain Topography - June 25, 2009 Category: Neuroscience Authors: Ramon C, Freeman WJ, Holmes M, Ishimaru A, Haueisen J, Schimpf PH, Rezvanian E Tags: Brain Topogr Source Type: journals

Cortical Connections Between Dorsal and Ventral Visual Streams in Humans: Evidence by TMS/EEG Co-Registration.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study, co-registration of Transcranial Magnetic Stimulation (TMS) and Electroencephalographic activity (EEG) has been used to investigate the spreading of cortical connections from the parietal cortex in healthy volunteers. TMS on the left parietal cortex activated a network of prefrontal regions in the contra-lateral hemisphere in a time range of 102-167 ms after the stimulus. Moreover, activation in the ipsi-lateral middle temporal and fusiform gyri was observed at 171-177 ms after delivery of TMS. Findings suggest the existence of late driven connections between parietal and prefrontal regions that could partial...
Source: Brain Topography - June 4, 2009 Category: Neuroscience Authors: Zanon M, Busan P, Monti F, Pizzolato G, Battaglini PP Tags: Brain Topogr Source Type: journals

The Possibility of Left Dominant Activation of the Sensorimotor Cortex During Lip Protrusion in Men.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study revealed the possibility that the left sensorimotor cortex was more closely involved in non-verbal mouth movement in men, suggesting sex-related differences in sensorimotor cortex activation. PMID: 19455411 [PubMed - as supplied by publisher] (Source: Brain Topography)
Source: Brain Topography - May 19, 2009 Category: Neuroscience Authors: Fukunaga A, Ohira T, Kamba M, Ogawa S, Akiyama T, Kawase T Tags: Brain Topogr Source Type: journals

Ten Years at the Multisensory Forum: Musings on the Evolution of a Field.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
PMID: 19452270 [PubMed - as supplied by publisher] (Source: Brain Topography)
Source: Brain Topography - May 18, 2009 Category: Neuroscience Authors: Foxe JJ, Molholm S Tags: Brain Topogr Source Type: journals

Age-Related Increase in Cross-Sensory Noise in Resting and Steady-State Cerebral Perfusion.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Behavioral research indicates that healthy aging is accompanied by maintenance of voluntary attentional function in many situations, suggesting older adults are able to use attention to enhance and suppress neural activity. However, other experiments show increased distractibility with age, suggesting a failure of attention. One hypothesis for these apparently conflicting findings is that older adults experience a greater sensory processing load at baseline compared to younger adults. In this situation, older adults might successfully modulate sensory cortical activity relative to a baseline referent condition, but the...
Source: Brain Topography - May 4, 2009 Category: Neuroscience Authors: Hugenschmidt CE, Mozolic JL, Tan H, Kraft RA, Laurienti PJ Tags: Brain Topogr Source Type: journals

In Memory of Paul Bertelson (1926-2008).Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
PMID: 19415482 [PubMed - as supplied by publisher] (Source: Brain Topography)
Source: Brain Topography - May 4, 2009 Category: Neuroscience Authors: Vroomen J, de Gelder B Tags: Brain Topogr Source Type: journals

Detecting Functional Connectivity in fMRI Using PCA and Regression Analysis.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A fMRI connectivity analysis approach combining principal component analysis (PCA) and regression analysis is proposed to detect functional connectivity between the brain regions. By first using PCA to identify clusters within the vectors of fMRI time series, more energy and information features in the signal can be maintained than using averaged values from brain regions of interest. Then, regression analysis can be applied to the extracted principal components in order to further investigate functional connectivity. Finally, t-test is applied and the patterns with t-values lager than a threshold are considered as fun...
Source: Brain Topography - April 30, 2009 Category: Neuroscience Authors: Zhong Y, Wang H, Lu G, Zhang Z, Jiao Q, Liu Y Tags: Brain Topogr Source Type: journals

Mismatch Negativity with Visual-only and Audiovisual Speech.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The functional organization of cortical speech processing is thought to be hierarchical, increasing in complexity and proceeding from primary sensory areas centrifugally. The current study used the mismatch negativity (MMN) obtained with electrophysiology (EEG) to investigate the early latency period of visual speech processing under both visual-only (VO) and audiovisual (AV) conditions. Current density reconstruction (CDR) methods were used to model the cortical MMN generator locations. MMNs were obtained with VO and AV speech stimuli at early latencies (approximately 82-87 ms peak in time waveforms relative to the ac...
Source: Brain Topography - April 29, 2009 Category: Neuroscience Authors: Ponton CW, Bernstein LE, Auer ET Tags: Brain Topogr Source Type: journals

The Principle of Inverse Effectiveness in Multisensory Integration: Some Statistical Considerations.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The principle of inverse effectiveness (PoIE) in multisensory integration states that, as the responsiveness to individual sensory stimuli decreases, the strength of multisensory integration increases. I discuss three potential problems in the analysis of multisensory data with regard to the PoIE. First, due to 'regression towards the mean,' the PoIE may often be observed in datasets that are analysed post-hoc (i.e., when sorting the data by the unisensory responses). The solution is to design discrete levels of stimulus intensity a priori. Second, due to neurophysiological or methodological constraints on responsivene...
Source: Brain Topography - April 28, 2009 Category: Neuroscience Authors: Holmes NP Tags: Brain Topogr Source Type: journals

"Touched" by Light: Event-Related Potentials (ERPs) to Visuo-Haptic Stimuli in Peri-Personal Space.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study, we examined event-related potentials (ERPs) elicited by laser dots projected onto or above participants' index and middle fingers during a sustained-attention task. We hypothesized that visual stimuli projected onto the hand would elicit differences in ERP deflections related to sensory gating and categorization in comparison to when projected close to the hand. Participants responded via a footswitch to rare target flashes of light occurring on or directly above the middle finger of the attended hand. We found enhanced amplitudes of the N1 and P3 deflections when the stimuli fell onto the finger tips as opp...
Source: Brain Topography - April 28, 2009 Category: Neuroscience Authors: Simon-Dack SL, Cummings SE, Reetz DJ, Alvarez-Vazquez E, Gu H, Teder-Sälejärvi WA Tags: Brain Topogr Source Type: journals

Audiovisual Non-Verbal Dynamic Faces Elicit Converging fMRI and ERP Responses.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In an everyday social interaction we automatically integrate another's facial movements and vocalizations, be they linguistic or otherwise. This requires audiovisual integration of a continual barrage of sensory input-a phenomenon previously well-studied with human audiovisual speech, but not with non-verbal vocalizations. Using both fMRI and ERPs, we assessed neural activity to viewing and listening to an animated female face producing non-verbal, human vocalizations (i.e. coughing, sneezing) under audio-only (AUD), visual-only (VIS) and audiovisual (AV) stimulus conditions, alternating with Rest (R). Underadditive ef...
Source: Brain Topography - April 22, 2009 Category: Neuroscience Authors: Brefczynski-Lewis J, Lowitszch S, Parsons M, Lemieux S, Puce A Tags: Brain Topogr Source Type: journals

Peripersonal Space and Body Schema: Two Labels for the Same Concept?Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
To sensibly interact with the environment, like when grasping objects and navigating through space, the brain needs to compute not only target- and environment-related inputs, but also the size and spatial location of the entire body as well as of its parts. The neuronal construction and dynamic updating throughout the entire life of this bodily representation, commonly termed body schema in the literature, appears essential for efficient motor control and skilful tool-use. Meanwhile, recent contributions to the study of spatial multisensory processing have identified the peripersonal space as a particular region surro...
Source: Brain Topography - April 22, 2009 Category: Neuroscience Authors: Cardinali L, Brozzoli C, Farnè A Tags: Brain Topogr Source Type: journals

Time-Window-of-Integration (TWIN) Model for Saccadic Reaction Time: Effect of Auditory Masker Level on Visual-Auditory Spatial Interaction in Elevation.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Saccadic reaction time (SRT) to a visual target tends to be shorter when auditory stimuli are presented in close temporal and spatial proximity, even when subjects are instructed to ignore the auditory non-target (focused attention paradigm). Previous studies using pairs of visual and auditory stimuli differing in both azimuth and vertical position suggest that the amount of SRT facilitation decreases not with the physical but with the perceivable distance between visual target and auditory non-target. Steenken et al. (Brain Res 1220:150-156, 2008) presented an additional white-noise masker background of three seconds ...
Source: Brain Topography - April 1, 2009 Category: Neuroscience Authors: Colonius H, Diederich A, Steenken R Tags: Brain Topogr Source Type: journals

A Putative Model of Multisensory Object Representation.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This review surveys the recent literature on visuo-haptic convergence in the perception of object form, with particular reference to the lateral occipital complex (LOC) and the intraparietal sulcus (IPS) and discusses how visual imagery or multisensory representations might underlie this convergence. Drawing on a recent distinction between object- and spatially-based visual imagery, we propose a putative model in which LOtv, a subregion of LOC, contains a modality-independent representation of geometric shape that can be accessed either bottom-up from direct sensory inputs or top-down from frontoparietal regions. We su...
Source: Brain Topography - March 28, 2009 Category: Neuroscience Authors: Lacey S, Tal N, Amedi A, Sathian K Tags: Brain Topogr Source Type: journals

Negative BOLD in Sensory Cortices During Verbal Memory: A Component in Generating Internal Representations?Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
People tend to close their eyes when trying to retrieve an event or a visual image from memory. However the brain mechanisms behind this phenomenon remain poorly understood. Recently, we showed that during visual mental imagery, auditory areas show a much more robust deactivation than during visual perception. Here we ask whether this is a special case of a more general phenomenon involving retrieval of intrinsic, internally stored information, which would result in crossmodal deactivations in other sensory cortices which are irrelevant to the task at hand. To test this hypothesis, a group of 9 sighted individuals were...
Source: Brain Topography - March 27, 2009 Category: Neuroscience Authors: Azulay H, Striem E, Amedi A Tags: Brain Topogr Source Type: journals

Not Just for Bimodal Neurons Anymore: The Contribution of Unimodal Neurons to Cortical Multisensory Processing.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Traditionally, neuronal studies of multisensory processing proceeded by first identifying neurons that were overtly multisensory (e.g., bimodal, trimodal) and then testing them. In contrast, the present study examined, without precondition, neurons in an extrastriate visual area of the cat for their responses to separate (visual, auditory) and combined-modality (visual and auditory) stimulation. As expected, traditional bimodal forms of multisensory neurons were identified. In addition, however, many neurons that were activated only by visual stimulation (i.e., unimodal) had that response modulated by the presence of a...
Source: Brain Topography - March 27, 2009 Category: Neuroscience Authors: Allman BL, Keniston LP, Meredith MA Tags: Brain Topogr Source Type: journals

An Investigation of the Relationship Between fMRI and ERP Source Localized Measurements of Brain Activity during Face Processing.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Brain activity patterns during face processing have been extensively explored with functional magnetic resonance imaging (fMRI) and event-related potentials (ERPs). ERP source localization adds a spatial dimension to the ERP time series recordings, which allows for a more direct comparison and integration with fMRI findings. The goals for this study were (1) to compare the spatial descriptions of neuronal activity during face processing obtained with fMRI and ERP source localization using low-resolution electromagnetic tomography (LORETA), and (2) to use the combined information from source localization and fMRI to exp...
Source: Brain Topography - March 26, 2009 Category: Neuroscience Authors: Corrigan NM, Richards T, Webb SJ, Murias M, Merkle K, Kleinhans NM, Johnson LC, Poliakov A, Aylward E, Dawson G Tags: Brain Topogr Source Type: journals

Mechanisms and Applications of Theta-burst rTMS on the Human Motor Cortex.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This article highlights current hypotheses regarding the mechanisms of action of TBS and some central factors which may influence cortical responses to TBS. Furthermore, previous and ongoing research performed in the field of TBS on the motor cortex is summarized. PMID: 19288184 [PubMed - as supplied by publisher] (Source: Brain Topography)
Source: Brain Topography - March 14, 2009 Category: Neuroscience Authors: Cárdenas-Morales L, Nowak DA, Kammer T, Wolf RC, Schönfeldt-Lecuona C Tags: Brain Topogr Source Type: journals

Pre-attentive Spectro-temporal Feature Processing in the Human Auditory System.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In the present study, we investigated the pre-attentive processing of low-level acoustic properties and the impact of this mechanism on functional lateralization in the human auditory system. Mismatch negativity (MMN) of the event-related potentials (ERP) were recorded in 19 adult humans who passively listened to a standard stimulus and spectrally and temporally deviant sounds. We predicted modulations of the MMN amplitude in response to spectrally and temporally graded deviants. Based on recent models of functional hemispheric lateralisation, we further hypothesized a left-lateralized source of the MMN in response to ...
Source: Brain Topography - March 6, 2009 Category: Neuroscience Authors: Zaehle T, Jancke L, Herrmann CS, Meyer M Tags: Brain Topogr Source Type: journals

Combining TMS and EEG Offers New Prospects in Cognitive Neuroscience.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The combination of brain stimulation by transcranial magnetic stimulation (TMS) with simultaneous electroencephalographic (EEG) imaging has become feasible due to recent technical developments. The TMS-EEG integration provides real-time information on cortical reactivity and connectivity through the analysis of TMS-evoked potentials (TEPs), and how functional activity links to behavior through the study of TMS-induced modulations thereof. It reveals how these effects vary as a function of neuronal state, differing between individuals and patient groups but also changing rapidly over time during task performance. This r...
Source: Brain Topography - February 25, 2009 Category: Neuroscience Authors: Miniussi C, Thut G Tags: Brain Topogr Source Type: journals

Saccade Related Gamma-Band Activity in Intracerebral EEG: Dissociating Neural from Ocular Muscle Activity.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Recent evidence suggests that transient increases in scalp electroencephalography (EEG) gamma band power (above 30 Hz) can be due to miniature eye movements. Although, these findings do not raise doubts about the widely established role of gamma range neural synchrony, it does call for caution when it comes to interpreting high frequency scalp EEG data. By contrast, gamma-band activity detected with intracerebral EEG (iEEG) is assumed to be immune to such miniature saccade artefacts. Here, we show for the first time, that while this is indeed largely the case, intracerebral recordings in the temporal pole of implanted ...
Source: Brain Topography - February 21, 2009 Category: Neuroscience Authors: Jerbi K, Freyermuth S, Dalal S, Kahane P, Bertrand O, Berthoz A, Lachaux JP Tags: Brain Topogr Source Type: journals

The Broadband-Transient Induced Gamma-Band Response in Scalp EEG Reflects the Execution of Saccades.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The contraction of the extra-ocular muscles, during the execution of saccades, produces a strong electric potential in the EEG called the saccadic spike potential (SP). At the frequency spectrum, this SP manifests as a broadband response with most of its power at the gamma-band frequencies. Saccadic activity is known to follow a time-pattern of repression (at around 50-150 ms post stimulus) which is followed by a large increase in saccadic rate at around 200-300 ms post stimulus. Due to this temporal pattern relative to the stimulus, and to the appearance of a SP at each saccade, this increase in saccadic rate shows up...
Source: Brain Topography - February 21, 2009 Category: Neuroscience Authors: Yuval-Greenberg S, Deouell LY Tags: Brain Topogr Source Type: journals

Relation of Gamma Oscillations in Scalp Recordings to Muscular Activity.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We recorded scalp electrical activity before and after full neuro-muscular paralysis in 5 volunteers and determined differences due to elimination of muscular activity on several standard applications of EEG. Due to paralysis, there were reductions in 'noisiness' of the standard scalp recordings which were maximal over the peripheral scalp, not explained by abolition of movement artefact, and best accounted for by sustained EMG activity in resting individuals. There was a corresponding reduction in spectral power in the gamma range. In central leads, the extent of gamma frequency coherence during a non-time-locked ment...
Source: Brain Topography - February 20, 2009 Category: Neuroscience Authors: Pope KJ, Fitzgibbon SP, Lewis TW, Whitham EM, Willoughby JO Tags: Brain Topogr Source Type: journals

Electromyogenic Artifacts and Electroencephalographic Inferences.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Muscle or electromyogenic (EMG) artifact poses a serious risk to inferential validity for any electroencephalography (EEG) investigation in the frequency-domain owing to its high amplitude, broad spectrum, and sensitivity to psychological processes of interest. Even weak EMG is detectable across the scalp in frequencies as low as the alpha band. Given these hazards, there is substantial interest in developing EMG correction tools. Unfortunately, most published techniques are subjected to only modest validation attempts, rendering their utility questionable. We review recent work by our laboratory quantitatively investi...
Source: Brain Topography - February 12, 2009 Category: Neuroscience Authors: Shackman AJ, McMenamin BW, Slagter HA, Maxwell JS, Greischar LL, Davidson RJ Tags: Brain Topogr Source Type: journals

Discussing Gamma.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
PMID: 19212812 [PubMed - as supplied by publisher] (Source: Brain Topography)
Source: Brain Topography - February 11, 2009 Category: Neuroscience Authors: Michel CM, Murray MM Tags: Brain Topogr Source Type: journals

The Gamma Oscillation: Master or Slave?Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The idea that gamma enhancement reflects a state of high neuronal excitability and synchrony, critical for active brain operations, sets gamma up as a "master" or executor process that determines whether an input is effectively integrated and an effective output is generated. However, gamma amplitude is often coupled to the phase of lower frequency delta or theta oscillations, which would make gamma a "slave" to lower frequency activity. Gamma enslavement is productive and typical during rhythmic mode brain operations; when a predictable rhythm is in play, low and mid-frequency oscillations can be entrained and their e...
Source: Brain Topography - February 10, 2009 Category: Neuroscience Authors: Schroeder CE, Lakatos P Tags: Brain Topogr Source Type: journals

The Cortical Chronometry of Electrogustatory Event-related Potentials.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Electrogustometry (EGM) is the standard tool to assess gustatory functions in clinical environments. The stimulation elicits a percept often described as metallic, sour or salty, also referred to as electric taste. To date, the neuronal mechanisms that underlie electric taste perception are not yet fully understood. Electroencephalographic (EEG) approaches will certainly complement behavioral procedures and, furthermore, extend the understanding of gustatory processing in general and disturbances of gustatory functions in particular. We used anodal pulses applied to the tip of the participants' tongue while EEG was rec...
Source: Brain Topography - February 6, 2009 Category: Neuroscience Authors: Ohla K, Hudry J, le Coutre J Tags: Brain Topogr Source Type: journals

Reorganisation of the Right Occipito-Parietal Stream for Auditory Spatial Processing in Early Blind Humans. A Transcranial Magnetic Stimulation Study.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
It is well known that, following an early visual deprivation, the neural network involved in processing auditory spatial information undergoes a profound reorganization. In particular, several studies have demonstrated an extensive activation of occipital brain areas, usually regarded as essentially "visual", when early blind subjects (EB) performed a task that requires spatial processing of sounds. However, little is known about the possible consequences of the activation of occipitals area on the function of the large cortical network known, in sighted subjects, to be involved in the processing of auditory spatial in...
Source: Brain Topography - February 6, 2009 Category: Neuroscience Authors: Collignon O, Davare M, Olivier E, De Volder AG Tags: Brain Topogr Source Type: journals

Unmasking Word Processing with ERPs: Two Novel Linear Techniques for the Estimation of Temporally Overlapped Waveforms.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Masked priming experiments are frequently used to study automatic aspects of word processing. Direct measures of such processing obtained with functional neuroimaging techniques (ERPs, fMRI, etc.) need to isolate the neural activation related to relevant events when they are rapidly followed by others (a situation found in other popular paradigms such as the attentional blink and repetition blindness). Here we examine the assumption of "simple insertion", which underlies the use of subtraction to isolate components of temporally overlapping waveforms. We propose two novel linear methods and illustrate how they extract ...
Source: Brain Topography - February 5, 2009 Category: Neuroscience Authors: Catena A, Houghton G, Valdés B, Fuentes LJ Tags: Brain Topogr Source Type: journals

Correspondence of Visual Evoked Potentials with FMRI Signals in Human Visual Cortex.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
PMID: 19023662 [PubMed - as supplied by publisher] (Source: Brain Topography)
Source: Brain Topography - November 23, 2008 Category: Neuroscience Authors: Whittingstall K, Wilson D, Schmidt M, Stroink G Tags: Brain Topogr Source Type: journals

A New Method for Quantification and Assessment of Epileptiform Activity in EEG with Special Reference to Focal Nocturnal Epileptiform Activity.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study suggests a definition of SI that gives a semiautomatic and relatively robust algorithm for assessment. The method employs spike detection by means of template matching of the current source density estimate. The percentage of time within an epoch with interspike interval (ISI) below a given limit, usually 3 s, is returned as the SI. This is calculated during daytime and in non-REM sleep. The standard epoch length is 10 min. The parameter selection is discussed in the context of the influence of spikes and bursts on cognition. The described method gives reproducible results in routine use, gives clinical valuable...
Source: Brain Topography - November 13, 2008 Category: Neuroscience Authors: Larsson PG, Wilson J, Eeg-Olofsson O Tags: Brain Topogr Source Type: journals

Characterizing Dynamic Functional Connectivity Across Sleep Stages from EEG.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Following a nonlinear dynamics approach, we investigated the emergence of functional clusters which are related with spontaneous brain activity during sleep. Based on multichannel EEG traces from 10 healthy subjects, we compared the functional connectivity across different sleep stages. Our exploration commences with the conjecture of a small-world patterning, present in the scalp topography of the measured electrical activity. The existence of such a communication pattern is first confirmed for our data and then precisely determined by means of two distinct measures of non-linear interdependence between time-series. A...
Source: Brain Topography - November 13, 2008 Category: Neuroscience Authors: Dimitriadis SI, Laskaris NA, Del Rio-Portilla Y, Koudounis GC Tags: Brain Topogr Source Type: journals

Brain Electrical Source Differences between Depressed Subjects and Healthy Controls.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Many brain regions show metabolic and perfusion abnormalities in major depressive disorder (MDD), including anterior cingulate and prefrontal cortices. Some of these same areas also show abnormal function with low resolution electromagnetic tomography (LORETA). However, LORETA results are not always consistent across studies, nor with findings from other imaging modalities. These discrepancies may be due, among other factors, to the sensitivity of EEG source localization to different electrode montages. Thirty-six channel EEG was collected from healthy controls and age- and gender-matched unmedicated subjects with MDD ...
Source: Brain Topography - October 29, 2008 Category: Neuroscience Authors: Korb AS, Cook IA, Hunter AM, Leuchter AF Tags: Brain Topogr Source Type: journals

Correspondence of Visual Evoked Potentials with FMRI Signals in Human Visual Cortex.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study, we used a visual stimuli designed to shift cortical activity from anterior to posterior regions of the visual cortex. Using EEG and FMRI, we investigated how shifts in +BOLD and -BOLD location were correlated to shifts in the N75 and P100 visual evoked potential (VEP) dipolar sources. The results show that the N75 dipole along with +BOLD, were indeed shifted from posterior to anterior regions of the visual cortex. The P100 VEP component, along with the -BOLD were not shifted to the same extent, indicating that N75 is better correlated to +BOLD than to -BOLD. These findings indicate how different components o...
Source: Brain Topography - October 9, 2008 Category: Neuroscience Authors: Kevin W, Doug W, Matthias S, Gerhard S Tags: Brain Topogr Source Type: journals

The Effects of L: -theanine on Alpha-Band Oscillatory Brain Activity During a Visuo-Spatial Attention Task.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusions This pattern of results implies that L: -theanine plays a more general role in attentional processing, facilitating longer-lasting processes responsible for sustaining attention across the timeframe of a difficult task, rather than affecting specific moment-to-moment phasic deployment processes. PMID: 18841456 [PubMed - as supplied by publisher] (Source: Brain Topography)
Source: Brain Topography - October 9, 2008 Category: Neuroscience Authors: Gomez-Ramirez M, Kelly SP, Montesi JL, Foxe JJ Tags: Brain Topogr Source Type: journals

Impaired Imagery for Upper Limbs.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The brain processes associated with mental imagery have long been a matter of debate. Neuroimaging and neuropsychological studies have yielded diverging evidence of mental transformation activating the right hemisphere, the left hemisphere, or both. Here, using a mirror/normal discrimination task with rotated body parts (BPs) and external objects (EOs), we describe the case of a patient who developed a selective deficit in mental imagery of such BPs due to left posterior parietal brain damage. In addition, the patient's deficit predominated for pictures of right arms (i.e., arms corresponding to the patient's imagined ...
Source: Brain Topography - September 18, 2008 Category: Neuroscience Authors: Overney LS, Blanke O Tags: Brain Topogr Source Type: journals

State-Dependency of Transcranial Magnetic Stimulation.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Transcranial magnetic stimulation (TMS), a tool that allows noninvasive modulation of cortical neural activity, has become an important tool in cognitive neuroscience and is being increasingly explored in neurotherapeutics. Amongst the factors that are likely to influence its efficacy, the importance of the baseline cortical activation state on the impact of TMS has not received much attention. However, this state-dependency is important as the neural impact of any external stimulus represents an interaction with the ongoing brain activity at the time of stimulation. The effects of any external stimulus are therefore n...
Source: Brain Topography - September 13, 2008 Category: Neuroscience Authors: Silvanto J, Pascual-Leone A Tags: Brain Topogr Source Type: journals

Parvocellular and Magnocellular Contributions to the Initial Generators of the Visual Evoked Potential: High-Density Electrical Mapping of the "C1" Component.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The C1 component of the VEP is considered to index initial afference of retinotopic regions of human visual cortex (V1 and V2). C1 onsets over central parieto-occipital scalp between 45 and 60 ms, peaks between 70 and 100 ms, and then resolves into the following P1 component. By exploiting isoluminant and low-contrast luminance stimuli, we assessed the relative contributions of the Magnocellular (M) and Parvocellular (P) pathways to generation of C1. C1 was maximal at 88 ms in a 100% luminance contrast condition (which stimulates both P and M pathways) and at 115 ms in an isoluminant chromatic condition (which isolates...
Source: Brain Topography - September 11, 2008 Category: Neuroscience Authors: Foxe JJ, Strugstad EC, Sehatpour P, Molholm S, Pasieka W, Schroeder CE, McCourt ME Tags: Brain Topogr Source Type: journals

EEG Correlates of Action Observation in Humans.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
To investigate electrophysiological correlates of action observation electroencephalogram (EEG) was recorded while participants observed repetitive biological (human) or non-biological movements (at a rate of 2 Hz). Steady-state evoked potentials were analyzed and their neural sources were investigated using low resolution electromagnetic tomography analysis (LORETA). Results revealed significantly higher activation in the primary motor and premotor cortex, supplementary motor area as well as the posterior parietal cortices during observation of biological movements, supporting mirror properties of cortical motor neuro...
Source: Brain Topography - September 9, 2008 Category: Neuroscience Authors: Holz EM, Doppelmayr M, Klimesch W, Sauseng P Tags: Brain Topogr Source Type: journals

Spatial Correspondence Between Functional MRI (fMRI) Activations and Cortical Current Density Maps of Event-Related Potentials (ERP): A Study with Four Tasks.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We investigated the spatial correspondence between functional MRI (fMRI) activations and cortical current density maps of event-related potentials (ERPs) reconstructed without fMRI priors. The presence of a significant spatial correspondence is a prerequisite for direct integration of the two modalities, enabling to combine the high spatial resolution of fMRI with the high temporal resolution of ERPs. Four separate tasks were employed: visual stimulation with a pattern-reversal chequerboard, recognition of images of nameable objects, recognition of written words, and auditory stimulation with a piano note. ERPs were ac...
Source: Brain Topography - August 29, 2008 Category: Neuroscience Authors: Minati L, Rosazza C, Zucca I, D'Incerti L, Scaioli V, Bruzzone MG Tags: Brain Topogr Source Type: journals

Working Memory in Schizophrenia: An EEG Study Using Power Spectrum and Coherence Analysis to Estimate Cortical Activation and Network Behavior.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study examined regional cortical activations and cortico-cortical connectivity in a group of 20 high-functioning patients with schizophrenia and 20 healthy controls matched for age and sex during a 0- and a 2-back working memory (WM) task. An earlier study comparing schizophrenia patients with education level-matched healthy controls revealed less "optimally" organized network during the 2-back task, whereas a second study with healthy volunteers had suggested that the degree of cortical organization may be inversely proportional to educational level (less optimal functional connectivity in better educated individuals...
Source: Brain Topography - August 26, 2008 Category: Neuroscience Authors: Pachou E, Vourkas M, Simos P, Smit D, Stam CJ, Tsirka V, Micheloyannis S Tags: Brain Topogr Source Type: journals