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852 records returned

Cystatin C in macular and neuronal degenerations: Implications for mechanism(s) of Age-related Macular Degeneration.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Cystatin C is a strong inhibitor of cysteine proteinases expressed by diverse cells. Variant B cystatin C, which was associated with increased risk of developing age-related macular degeneration, differs from the wild type protein by a single amino acid (A25T) in the signal sequence responsible for its targeting to the secretory pathway. The same variant conveys susceptibility to Alzheimer disease. Our investigations of the trafficking and processing of variant B cystatin C in living RPE cells highlight impaired secretion of extracellular modulators and inappropriate protein retention in RPE cells as potential molecula...
Source: Vision Research - November 13, 2009 Category: Opthalmology Authors: Paraoan L, Hiscott P, Gosden C, Grierson I Tags: Vision Res Source Type: journals

Binocular Coordination during Scanning of Simple Dot Stimuli.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We examined the influence of a variety of visual factors on binocular coordination during saccadic orienting. Some experimental conditions placed similar demands on the oculomotor system as those that occur during reading, but in the absence of linguistic processing. We examined whether saccade target extent, preceding saccade magnitude, preceding saccade direction, and parafoveal availability of saccade target influenced fixation disparity. Disparities similar in magnitude and frequency to those obtained in previous binocular reading experiments occurred. Saccade magnitude had a robust influence upon fixation disparities....
Source: Vision Research - November 12, 2009 Category: Opthalmology Authors: Kirkby JA, Blythe HI, Benson V, Liversedge SP Tags: Vision Res Source Type: journals

Surface Boundary Contour Strengthens Image Dominance in Binocular Competition.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We used a binocular rivalry stimulus with one half-image having a vertical grating disc surrounded by horizontal grating, and the other half-image having a horizontal grating disc with a variable spatial phase relative to the surrounding horizontal grating. We found that increasing the phase-shift of the horizontal grating disc, which strengthens the boundary contour, progressively increases its predominance. But the predominance is little affected when a constant gray ring (boundary contour) is added onto the rim of the incrementally phase-shifted horizontal grating. This suggests the influence of boundary contour sup...
Source: Vision Research - November 10, 2009 Category: Opthalmology Authors: Xu JP, He ZJ, Ooi TL Tags: Vision Res Source Type: journals

A Landmark Effect in the Perceived Displacement of Objects.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Perceiving the displacement of an object after a visual distraction is an essential ability to interact with the world. Previous research has shown a bias to perceive the first object seen after a saccade as stable while the second one moving (landmark effect). The present study examines the generality and nature of this phenomenon. The landmark effect was observed in the absence of eye movements, when the two objects were obscured by a blank screen, a moving pattern mask, or simply disappeared briefly before reappearing one after the other. The first reappearing object was not required to remain visible while the seco...
Source: Vision Research - November 9, 2009 Category: Opthalmology Authors: Higgins JS, Wang RF Tags: Vision Res Source Type: journals

Form overshadows 'opponent motion' information in processing of biological motion from point light walker stimuli.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The point light walker (PLW) has been taken to demonstrate the existence of mechanisms specialised in the processing of biological motion, but the roles of form and motion information in such processing remain unclear. While processing is robust to distortion and exclusion of the local motion signals of the individual elements of the PLW, the motion relationships between the elements - referred to as opponent motion - have been suggested to be crucial. By using Gabor patches oriented in relation to the opponent motion paths as the elements of the PLW, the influence of form and opponent motion information on biological ...
Source: Vision Research - November 9, 2009 Category: Opthalmology Authors: Thirkettle M, Scott-Samuel NE, Benton CP Tags: Vision Res Source Type: journals

Cue Conflict Between Disparity Change and Looming in the Perception of Motion in Depth.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We hypothesized that it is the conflict between various cues to distance that have produced results purportedly showing that vergence eye movements induced by disparity change are not an effective cue for depth. Single and compound stimuli were used to examine the perceived motion in depth (MID) produced by simulated motion oscillations specified by disparity, relative disparity, and/or looming. Estimations of the extent of MID and binocularly recorded eye movements showed that the vergence induced by disparity change is indeed an effective cue for motion in depth in conditions where looming information does not confli...
Source: Vision Research - November 9, 2009 Category: Opthalmology Authors: González EG, Allison RS, Ono H, Vinnikov M Tags: Vision Res Source Type: journals

Paradoxical Lightness Contrast.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The visual system's computation of lightness (perceived reflectance) leads to contrast effects in which a gray target region appears lighter on a black background than on a white one. Here we show a paradoxical contrast effect in which targets look lighter after adding regions that increase the scene's average luminance, and darker after adding regions that decrease this luminance. The paradoxical effect emerges if the target sits either on a black local background surrounded by a white remote background, or on a white local background surrounded by a black remote background. It does not occur if both backgrounds have ...
Source: Vision Research - November 5, 2009 Category: Opthalmology Authors: Kramer P, Bressan P Tags: Vision Res Source Type: journals

New "Golden" Ratios for Facial Beauty.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In four experiments, we tested the existence of an ideal facial feature arrangement that could optimize the attractiveness of any face given its facial features. Participants made paired comparisons of attractiveness between faces with identical facial features but different eye-mouth distances and different interocular distances. We found that although different faces have varying attractiveness, individual attractiveness is optimized when the face's vertical distance between the eyes and the mouth is approximately 36% of its length, and the horizontal distance between the eyes is approximately 46% of the face's width...
Source: Vision Research - November 5, 2009 Category: Opthalmology Authors: Pallett PM, Link S, Lee K Tags: Vision Res Source Type: journals

Peripheral Sensitivity to Biological Motion Conveyed by First and Second-order Signals.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
There is evidence that human observers are more sensitive to the direction-of-heading of point-light walkers defined by first-order than second-order motions. We addressed this question by measuring the minimum direction difference (azimuth) that observers could discriminate when the dots composing the walkers were conveyed by first or second-order motions. Sensitivity to azimuth differences for four stimulus types (two first-order and two second-order) was tested at a range of stimulus sizes and at eccentricities of 0 to 16 degrees in the right visual field. We find that for most stimulus types and eccentricities any ...
Source: Vision Research - November 3, 2009 Category: Opthalmology Authors: Gurnsey R, Troje NF Tags: Vision Res Source Type: journals

Reaction time distributions constrain models of visual search.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Many experiments have investigated visual search for simple stimuli like colored bars or alphanumeric characters. When eye movements are not a limiting factor, these tasks tend to produce roughly linear functions relating reaction time (RT) to the number of items in the display (set size). The slopes of the RT x set size functions for different searches fall on a continuum from highly efficient (slopes near zero) to inefficient (slopes > 25-30 msec/item). Many theories of search can produce the correct pattern of mean RTs. Producing the correct RT distributions is more difficult. In order to guide future modeling, w...
Source: Vision Research - November 3, 2009 Category: Opthalmology Authors: Wolfe JM, Palmer EM, Horowitz TS Tags: Vision Res Source Type: journals

Priming of pop-out modulates attentional target selection in visual search: Behavioural and electrophysiological evidence.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Previous behavioural studies have shown that the repetition of target or distractor features across trials speeds pop-out visual search. We obtained behavioural and event-related brain potential (ERP) measures in two experiments where participants searched for a colour singleton target among homogeneously coloured distractors. An ERP marker of spatially selective attention (N2pc component) was delayed when either target or distractor colours were swapped across successive trials, demonstrating that intertrial feature priming systematically affects the onset of focal-attentional target processing. Results support the hy...
Source: Vision Research - November 3, 2009 Category: Opthalmology Authors: Eimer M, Kiss M, Cheung T Tags: Vision Res Source Type: journals

Vision Research reviews 'vision research'.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
PMID: 19878768 [PubMed - in process] (Source: Vision Research)
Source: Vision Research - November 1, 2009 Category: Opthalmology Authors: Levi DM Tags: Vision Res Source Type: journals

Learning Motion: Human vs Optimal Bayesian Learner.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We used the optimal perceptual learning paradigm (Eckstein, Abbey, Pham, & Shimozaki, 2004) to investigate the dynamics of human rapid learning processes in motion discrimination tasks and compare it to an optimal Bayesian learner. This paradigm consists of blocks of few trials defined by a set of target attributes, and it has been shown its ability to detect learning effects appearing as soon as after the first trial. In the present task a sequence consisting of four patches containing random-dot patterns is presented at four separate locations equidistant from a fixation point. On each trial, the random dots in t...
Source: Vision Research - October 30, 2009 Category: Opthalmology Authors: Trenti EJ, Barraza JF, Eckstein MP Tags: Vision Res Source Type: journals

Graded Recognition as a Function of the Number of Target Fixations.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Target recognition stages were studied by exposing observers to varying controlled numbers of target fixations. The target, present in half the displays, consisted of two identical cards (Identity Search Task; Jacob & Hochstein, 2009). Following more fixations, targets are better recognized, indicated by increased Hit rate and detectability (according to Unequal Variance Signal Detection Theory), decreased Response Time and growing confidence, reflecting current stage in recognition process. Thus, gathering information over a specific scene region results from a growing number of fixations on that particular region...
Source: Vision Research - October 30, 2009 Category: Opthalmology Authors: Jacob M, Hochstein S Tags: Vision Res Source Type: journals

Cone photopigment variations in Cebus apella monkeys evidenced by electroretinogram measurements and genetic analysis.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We investigated the color vision pattern in Cebus apella monkeys by means of electroretinogram measurements (ERG) and genetic analysis. Based on ERG we could discriminate among three types of dichromatic males. Among females, this classification is more complex and requires additional genetic analysis. We found five among ten possible different phenotypes, two trichromats and three dichromats. We also found that Cebus present a new allele with spectral peak near 552 nm, with the amino acid combination SFT at positions 180, 277 and 285 of the opsin gene, in addition to the previously described SYT, AFT and AFA alleles. ...
Source: Vision Research - October 30, 2009 Category: Opthalmology Authors: G M Soares J, Fiorani M, Araujo EA, Zana Y, Bonci DM, Neitz M, Ventura DF, Gattass R Tags: Vision Res Source Type: journals

The Modulation of Perceptual Selection by Working Memory is Dependent on the Focus of Spatial Attention.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Recent research suggests that visual selection can be automatically biased to those stimuli matching the contents of working memory (WM). However, a complete functional account of the interplay between WM and attention remains to be established. In particular, the boundary conditions of the WM-effect on selection are unclear. Here, the authors investigate the influence of the focus of spatial attention (i.e., diffused vs. focused) by assessing the effect of spatial precues on attentional capture by WM. Experiments 1 and 2 showed that relative to a neutral condition without memory-matching stimuli, the presence of a mem...
Source: Vision Research - October 30, 2009 Category: Opthalmology Authors: Pan Y, Soto D Tags: Vision Res Source Type: journals

Inhibition of masked primes as revealed by saccade curvature.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In masked priming, responses are often speeded when primes are similar to targets ('positive compatibility effect'). However, sometimes similarity of prime and target impairs responses ('negative compatibility effect'). A similar distinction has been found for the curvature of saccade trajectories. Here, we test whether the same inhibition processes are involved in the two phenomena, by directly comparing response times and saccade curvature within the same masked priming paradigm. Interestingly, we found a dissociation between the directions of masked priming and saccade curvature, which could indicate that multiple t...
Source: Vision Research - October 24, 2009 Category: Opthalmology Authors: Hermens F, Sumner P, Walker R Tags: Vision Res Source Type: journals

The Capsule Drug Device: Novel Approach for Drug Delivery to the Eye.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The objective of this study was to develop a novel intraocular implant for drug delivery. The capsule drug ring is a reservoir inserted in the lens capsule during cataract surgery, refillable and capable of delivering multiple drugs. Avastin(R) was the drug of interest in this study. Prototypes were manufactured using polymethylmethacrylate sheets as the reservoir material, a semipermeable membrane for controlled delivery and silicone check valves for refilling. The device showed near-zero-order release kinetics and Avastin(R) stability was investigated with accelerated temperature studies. PMID: 19854210 [PubMed - as ...
Source: Vision Research - October 22, 2009 Category: Opthalmology Authors: Molokhia SA, Sant H, Simonis J, Bishop CJ, Burr RM, Gale BK, Ambati BK Tags: Vision Res Source Type: journals

The Value of Measurement of Macular Carotenoid Pigment Optical Densities and Distributions in Age-Related Macular Degeneration and Other Retinal Disorders.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
There is increasing recognition that the optical and antioxidant properties of the xanthophyll carotenoids lutein and zeaxanthin play an important role in maintaining the health and function of the human macula. In this review article, we assess the value of non-invasive quantification of macular pigment levels and distributions to identify individuals potentially at risk for visual disability or catastrophic vision loss from age-related macular degeneration, and we consider the strengths and weaknesses of the diverse measurement methods currently available. PMID: 19854211 [PubMed - as supplied by publisher] (Source: Vision Research)
Source: Vision Research - October 22, 2009 Category: Opthalmology Authors: Bernstein PS, Delori FC, Richer S, Kuijk FJ, Wenzel AJ Tags: Vision Res Source Type: journals

Contribution of voltage-gated sodium channels to b- and d-waves of frog electroretinogram under different conditions of light adaptation.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The effect of blockade of voltage-gated sodium (Na(v)) channels by tetrodotoxin (TTX) on the V-log I function of the ERG b- and d-waves was investigated in light and dark adapted frog eyecups. TTX diminished the b- and d-wave amplitude under both conditions of adaptation at all stimulus intensities except for the middle intensity range in dark adapted eyes, where it had no effect on the b-wave amplitude. TTX delayed the time course of the responses, obtained with low intensity stimuli and widened the dynamic range of the b-wave. The inhibitory effect of TTX on the cone-mediated, but not rod-mediated b- and d-wave ampli...
Source: Vision Research - October 22, 2009 Category: Opthalmology Authors: Popova E, Kupenova P Tags: Vision Res Source Type: journals

A Unified Model of Illusory and Occluded Contour Interpolation.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Models of contour interpolation have been proposed for illusory contour interpolation but seldom for interpolation of occluded contours. The identity hypothesis [Kellman Loukides 1987 Kellman:Shipley 1991] posits that an early interpolation mechanism is shared by interpolated contours that are ultimately perceived as either illusory or occluded. Here we propose a model of such a unified interpolation mechanism for illusory and occluded contours, building on the framework established in Heitger:vonderHeydt [1998]. We show that a single, neurally plausible mechanism that is consistent with the identity hypothesis also ge...
Source: Vision Research - October 20, 2009 Category: Opthalmology Authors: Kalar DJ, Garrigan P, Wickens TD, Hilger JD, J Kellman P Tags: Vision Res Source Type: journals

The Influence of Intrinsically Photosensitive Retinal Ganglion Cells on the Spectral Sensitivity and Response Dynamics of the Human Pupillary Light Reflex.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study was therefore designed to examine the relative contribution of rod, cone and the melanopsin photoresponses of ipRGCs to the human PLR. We establish that the melanopsin photoresponse of ipRGCs contributes significantly to the maintenance of half maximal pupilloconstriction in response to light stimuli of 30 seconds or longer, even at low photopic irradiances. Furthermore, we show that the melanopsin photoresponse contributes significantly to three- quarter maximal pupilloconstriction in response to light stimuli as short as 2 seconds. We also demonstrate that cone photoresponses driving pupilloconstriction adapt ...
Source: Vision Research - October 18, 2009 Category: Opthalmology Authors: McDougal DH, Gamlin PD Tags: Vision Res Source Type: journals

Differential development of visual attention skills in school-age children.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Children aged 7-17 years and adults aged 18-22 years were tested on three aspects of visual attention: the ability to distribute visual attention across the field to search for a target, the time required for attention to recover from being directed towards a target, and the number of objects to which attention can be simultaneously allocated. The data suggested different developmental trajectories for these components of visual attention within the same set of participants. This suggests that, to some extent, spatial, temporal and object-based attentional processes are subserved by different neural resources which dev...
Source: Vision Research - October 13, 2009 Category: Opthalmology Authors: Dye MW, Bavelier D Tags: Vision Res Source Type: journals

Modulatory effects of binocular disparity and aging upon the perception of speed.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Two experiments investigated modulatory effects of a surround upon the perceived speed of a moving central region. Both the surround's depth and velocity (relative to the center) were manipulated. The abilities of younger observers (mean age was 23.1 years) were evaluated in Experiment 1, while Experiment 2 was devoted to older participants (mean age was 71.3 years). The results of Experiment 1 revealed that changes in the perceived depth of a surround (in this case caused by changes in binocular disparity) significantly influence the perceived speed of a central target. In particular, the center's motion was perceived...
Source: Vision Research - October 13, 2009 Category: Opthalmology Authors: Norman JF, Burtonm CL, Best LA Tags: Vision Res Source Type: journals

Landmarks facilitate visual space constancy across saccades and during fixation.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
It has been demonstrated that visual objects that are present after saccadic eye movements act as landmarks for the localization of stimuli across saccades, facilitating space constancy (Deubel, 2004). We here study the temporal conditions under which landmark effects occur after saccadic eye movements, and during fixation. Two small objects were presented 6 degrees in the periphery, one above the other. Observers saccaded to the space between them. One of the objects disappeared during the saccade and reappeared with a variable delay during or after the saccade. At the same time either that object or the continuously ...
Source: Vision Research - October 11, 2009 Category: Opthalmology Authors: Deubel H, Koch C, Bridgeman B Tags: Vision Res Source Type: journals

Characteristics of peripheral refractive errors of myopic and non-myopic chinese eyes.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Interest in peripheral refractive errors has increased as it was hypothesized that peripheral hypermetropia might provide a stimulus for axial elongation (Smith et al., 2005), this study was to determine relative peripheral refractive errors (RPRE) of the eyes of a group of Chinese children and adults. Central and peripheral (20, 30, 40 degrees at nasal, temporal, superior and inferior meridians of retina) refractive errors were obtained from cyclopleged eyes of 40 children and 42 adults with a Shin- Nippon Auto-refractor. Only right eyes were considered. Central spherical equivalent (M) was used to classify the eyes a...
Source: Vision Research - October 9, 2009 Category: Opthalmology Authors: Chen X, Sankaridurg P, Donovan L, Lin Z, Li L, Martinez A, Holden B, Ge J Tags: Vision Res Source Type: journals

Development of a training protocol to improve reading performance in peripheral vision.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
People with central-field loss must use peripheral vision for reading. Previous studies have shown that reading performance in peripheral vision can improve with extensive practice on a trigram letter-recognition task. The present study compared training on this task with training on two other character-based tasks (lexical decision and RSVP (Rapid Serial Visual Presentation) reading) which might plausibly produce more improvement in peripheral reading speed. Twenty-eight normally sighted young adults were trained at 10 degrees in the lower visual field in a pre/post design. All three training methods produced signific...
Source: Vision Research - October 7, 2009 Category: Opthalmology Authors: Yu D, Legge GE, Park H, Gage E, Chung ST Tags: Vision Res Source Type: journals

Individual set-point and gain of emmetropization in chickens.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
During the developmental process of emmetropization evidence shows that visual feedback guides the eye as it approaches a refractive state close to zero, or slightly hyperopic. How this "set-point" is internally defined, in the presence of continuous shifts of the focal plane with different viewing distances and accommodation, remains unclear. Minimizing defocus blur over time should produce similar end-point refractions in different individuals. However, we found that individual chickens display considerable variability in their set-point refractive states, despite that they all had the same visual experience. This va...
Source: Vision Research - October 7, 2009 Category: Opthalmology Authors: Tepelus TC, Schaeffel F Tags: Vision Res Source Type: journals

Attention directed by expectations enhances receptive fields in cortical area MT.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Expectations, especially those formed on the basis of extensive training, can substantially enhance visual performance. However, it is not clear that the physiological mechanisms underlying this enhancement are identical to those examined by experiments in which attention is directed by explicit instructions rather than strong expectations. To study the changes in visual representations associated with strong expectations, we trained animals to detect a brief motion pulse that was embedded in noise. Because the nature of the pulse and the statistics of its appearance were well known to the animals, they formed strong e...
Source: Vision Research - October 7, 2009 Category: Opthalmology Authors: Ghose GM, Bearl DW Tags: Vision Res Source Type: journals

How do amplitude spectra influence rapid animal detection?Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Amplitude spectra might provide information for natural scene classification. Amplitude does play a role in animal detection because accuracy suffers when amplitude is normalized. However, this effect could be due to an interaction between phase and amplitude, rather than to a loss of amplitude-only information. We used an amplitude-swapping paradigm to establish that animal detection is partly based on an interaction between phase and amplitude. A difference in false alarms for two subsets of our distractor stimuli suggests that the classification of scene environment (man-made versus natural) may also be based on an ...
Source: Vision Research - October 6, 2009 Category: Opthalmology Authors: Gaspar CM, Rousselet GA Tags: Vision Res Source Type: journals

Visual learning for perceptual and categorical decisions in the human brain.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Successful actions and interactions in the complex environments we inhabit entail making fast and optimal perceptual decisions. Extracting the key features from our sensory experiences and deciding how to interpret them is a computationally challenging task that is far from understood. Accumulating evidence suggests that the brain may solve this challenge by combining sensory information and previous knowledge about the environment acquired through evolution, development, and everyday experience. Here, we review the role of visual learning and experience-dependent plasticity in shaping decisions. We propose that learni...
Source: Vision Research - October 5, 2009 Category: Opthalmology Authors: Kourtzi Z Tags: Vision Res Source Type: journals

Effect of Sampling Array Irregularity and Window Size on the Discrimination of Sampled Gratings.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The effect of sampling irregularity and window size on orientation discrimination was investigated using discretely sampled gratings as stimuli. For regular sampling arrays, visual performance could be accounted for by a theoretical analysis of aliasing produced by undersampling. For irregular arrays produced by adding noise to the location of individual samples, the incidence of perceived orientation reversal declined and the spatial frequency range of flawless performance expanded well beyond the nominal Nyquist frequency. These results provide a psychophysical method to estimate the spatial density and the degree of...
Source: Vision Research - October 4, 2009 Category: Opthalmology Authors: Evans DW, Wang Y, Haggerty KM, Thibos LN Tags: Vision Res Source Type: journals

Differential Changes in Perceived Contrast Following Contrast Adaptation in Humans.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Perceived contrast is reduced after prolonged exposure to a textured pattern (contrast adaptation). The size of this effect is dependent on the relationship between the adapting contrast and the test contrast. It is generally accepted that the greatest reductions occur when the adapting contrast is much higher than the test contrast. Here this relationship was examined for a wide range of spatial frequencies. The results show that the effect of the adapt/test ratio on perceived contrast following contrast adaptation is highly spatial frequency dependent. At high spatial frequencies >1cpd perceived contrast was reduc...
Source: Vision Research - October 4, 2009 Category: Opthalmology Authors: Hietanen MA, Cloherty SL, Clifford CW, Ibbotson MR Tags: Vision Res Source Type: journals

New Approach to the Perception of 3D Shape Based on Veridicality, Complexity, Symmetry and Volume.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This paper reviews recent progress towards understanding 3D shape perception made possible by appreciating the significant role that veridicality and complexity play in the natural visual environment. The ability to see objects as they really are "out there" is derived from the complexity inherent in the 3D object's shape. The importance of both veridicality and complexity was ignored in most prior research. Appreciating their importance made it possible to devise a computational model that recovers the 3D shape of an object from only one of its 2D images. This model uses a simplicity principle consisting of only four ...
Source: Vision Research - September 30, 2009 Category: Opthalmology Authors: Pizlo Z, Sawada T, Li Y, Kropatsch W, Steinman RM Tags: Vision Res Source Type: journals

Low-level sensory plasticity during task-irrelevant perceptual learning: Evidence from conventional and double training procedures.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Studies of perceptual learning have focused on aspects of learning that are related to early stages of sensory processing. However, conclusions that perceptual learning results in low-level sensory plasticity are controversial, since such learning may also be attributed to plasticity in later stages of sensory processing or in readout from sensory to decision stages, or to changes in high-level central processing. To address this controversy, we developed a novel random dot motion (RDM) stimulus to target motion cells selective to contrast polarity by ensuring the motion direction information arises only from signal do...
Source: Vision Research - September 29, 2009 Category: Opthalmology Authors: Pilly PK, Grossberg S, Seitz AR Tags: Vision Res Source Type: journals

Photooxidation of rpe lipofuscin bisretinoids enhances fluorescence intensity.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We report that an increase in fluorescence emission can accompany photoxidation of the bisretinoids A2E and all-trans-retinal dimer. These findings are relevant to the quantification of RPE lipofuscin based on inference from fluorescence intensity. PMID: 19800359 [PubMed - as supplied by publisher] (Source: Vision Research)
Source: Vision Research - September 29, 2009 Category: Opthalmology Authors: Kim SR, Jang Y, Sparrow JR Tags: Vision Res Source Type: journals

Attention-based long-lasting sensitization and suppression of colors.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In contrast to the short-duration and quick reversibility of attention, a long-term sensitization to color based on protracted attention in a visual search task was reported by Tseng, Gobell, and Sperling (Nature, 2004). When subjects were trained for a few hours to search for a red object among colored distracters, sensitivity to red was increased for weeks. This sensitization was quantified using ambiguous motion displays containing isoluminant red-green and texture-contrast gratings, in which the perceived motion direction depended both on the attended color and on the relative red-green saturation. Such long-term e...
Source: Vision Research - September 27, 2009 Category: Opthalmology Authors: Tseng CH, Vidnyanszky Z, Papathomas T, Sperling G Tags: Vision Res Source Type: journals

Perceptual Learning And Attention: Reduction Of Object Attention Limitations With Practice.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Perceptual learning has widely been claimed to be attention driven; attention assists in choosing the relevant sensory information and attention may be necessary in many cases for learning. In this paper, we focus on the interaction of perceptual learning and attention - that perceptual learning can reduce or eliminate the limitations of attention, or, correspondingly, that perceptual learning depends on the attention condition. Object attention is a robust limit on performance. Two attributes of a single attended object may be reported without loss, while the same two attributes of different objects can exhibit a subs...
Source: Vision Research - September 27, 2009 Category: Opthalmology Authors: Dosher BA, Han S, Lu ZL Tags: Vision Res Source Type: journals

Contributions of visible persistence and perceptual set to the flash-lag effect: Focusing on flash onset abolishes the illusion.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Among other theories, visible persistence has been suggested to explain the flash-lag effect (FLE). According to this account, the flash is not compared to the moving object at its perceived onset, but at a later time while it is still subjectively visible. Therefore, it is reported to lag the moving object. We show that observers' perceptual set determines whether the persisting image of the flash or its onset is used to judge relative position. Spontaneously, observers use the persisting image, such that a flash-lag results. When forced to focus on the onset of the flash because flashes and stationary onset-only stim...
Source: Vision Research - September 25, 2009 Category: Opthalmology Authors: Gauch A, Kerzel D Tags: Vision Res Source Type: journals

Convergence of linkage, gene expression and association data demonstrates the influence of the RAR-related orphan receptor alpha (RORA) gene on neovascular AMD: A systems biology based approach.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
To identify novel genes and pathways associated with AMD, we performed microarray gene expression and linkage analysis which implicated the candidate gene, retinoic acid receptor-related orphan receptor alpha (RORA, 15q). Subsequent genotyping of 159 RORA single nucleotide polymorphisms (SNPs) in a family-based cohort, followed by replication in an unrelated case-control cohort, demonstrated that SNPs and haplotypes located in intron 1 were significantly associated with neovascular AMD risk in both cohorts. This is the first report demonstrating a possible role for RORA, a receptor for cholesterol, in the pathophysiolo...
Source: Vision Research - September 24, 2009 Category: Opthalmology Authors: Silveira AC, Morrison MA, Ji F, Xu H, Reinecke JB, Adams SM, Arneberg TM, Janssian M, Lee JE, Yuan Y, Schaumberg DA, Kotoula MG, Tsironi EE, Tsiloulis AN, Chatzoulis DZ, Miller JW, Kim IK, Hageman GH, Farrer LA, Haider NB, Deangelis MM Tags: Vision Res Source Type: journals

Transplantation of quantum dot-labelled bone marrow-derived stem cells into the vitreous of mice with laser-induced retinal injury: survival, integration and differentiation.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Accidental laser exposure to the eyes may result in serious visual impairment due to retina degeneration. Currently limited treatment is available for laser eye injury. In the current study, we investigated the therapeutic potential of bone marrow-derived stem cells (BMSCs) for laser-induced retinal trauma. Lineage negative bone marrow cells (Lin(-) BMCs) were labelled with quantum dots (Qdots) to track the cells in vivo. Lin(-) BMCs survived well after intravitreal injection. In vivo bromodeoxyuridine (BrdU) labeling showed these cells continued to proliferate and integrate into injured retinas. Furthermore, they expr...
Source: Vision Research - September 23, 2009 Category: Opthalmology Authors: Wang HC, Brown J, Alayon H, Stuck BE Tags: Vision Res Source Type: journals

The object and background hypothesis for vection.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We presented a motion-defined Rubin's vase to induce vection. Results clearly indicated that the background dominantly induced vection. We further demonstrated that motion stimuli that had a property of an object could not induce vection efficiently. Investigating vection in the framework of the object and background hypothesis provides a unified point of view for understanding vection stimuli. PMID: 19782099 [PubMed - as supplied by publisher] (Source: Vision Research)
Source: Vision Research - September 22, 2009 Category: Opthalmology Authors: Seno T, Ito H, Sunaga H Tags: Vision Res Source Type: journals

Saliency does not account for fixations to eyes within social scenes.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We assessed the role of saliency in driving observers to fixate the eyes in social scenes. Saliency maps (Itti & Koch, 2000) were computed for the scenes from three previous studies. Saliency provided a poor account of the data. The saliency values for the first-fixated locations were extremely low and no greater than what would be expected by chance. In addition, the saliency values for the eye regions were low. Furthermore, whereas saliency was no better at predicting early saccades than late saccades, the average latency to fixate social areas of the scene (e.g., the eyes) was very fast (within 200 msec). Thus, ...
Source: Vision Research - September 22, 2009 Category: Opthalmology Authors: Birmingham E, Bischof WF, Kingstone A Tags: Vision Res Source Type: journals

Oculomotor and Linguistic Determinants of Reading Development: A Longitudinal Study.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We longitudinally assessed the development of oculomotor control in reading from second to fourth grade by having children read sentences with embedded target words of varying length and frequency. Additionally, participants completed oculomotor (pro-/antisaccades) and linguistic tasks (word/picture naming), the latter containing the same item material as the reading task. Results revealed a 36% increase of reading efficiency. Younger readers utilized a global refixation strategy to gain more time for word decoding. Linguistic rather than oculomotor skills determined the development of reading abilities, although namin...
Source: Vision Research - September 21, 2009 Category: Opthalmology Authors: Huestegge L, Radach R, Corbic D, Huestegge SM Tags: Vision Res Source Type: journals

Sustained Convergence Induced Changes in Phoria and Divergence Dynamics.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusion: As a result of sustained convergence, phoria and divergence dynamics changed in a correlated manner. Such correlated changes in phoria and divergence dynamics are not explained by current models of disparity vergence eye movements. PMID: 19781567 [PubMed - as supplied by publisher] (Source: Vision Research)
Source: Vision Research - September 21, 2009 Category: Opthalmology Authors: Lee YY, Granger-Donetti B, Chang C, Alvarez TL Tags: Vision Res Source Type: journals

Inhibition of nitric oxide synthase desensitizes retinal ganglion cells to light by diminishing their excitatory synaptic currents under light adaptation.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The effect of inhibiting nitric oxide synthase (NOS) on the visual responses of mouse retinal ganglion cells (RGCs) was studied under light adaptation by using patch-clamp recordings. The results demonstrated that NOS inhibitor, L-NAME, reduced the sensitivity of RGCs to light under light adaptation at different ambient light conditions. These observations were seen in all cells that recordings were made from. L-NAME diminished the excitatory synaptic currents (EPSCs), rather than increasing the inhibitory synaptic currents, of RGCs to reduce the sensitivity of RGCs to light. Cones may be the sites that L-NAME acted to...
Source: Vision Research - September 18, 2009 Category: Opthalmology Authors: Nemargut JP, Wang GY Tags: Vision Res Source Type: journals

Anchoring gaze when categorizing faces' sex: Evidence from eye-tracking data.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Previous research has shown that during recognition of frontal views of faces, the preferred landing positions of eye fixations are either on the nose or the eye region. Can these findings generalize to other facial views and a simpler perceptual task? An eye-tracking experiment investigated categorization of the sex of faces seen in four views. The results revealed a strategy, preferred in all views, which consisted of focusing gaze within an 'infraorbital region' of the face. This region was fixated more in the first than in subsequent fixations. Males anchored gaze lower and more centrally than females. PMID: 19...
Source: Vision Research - September 2, 2009 Category: Opthalmology Authors: Sæther L, Belle WV, Laeng B, Brennen T, Overvoll M Tags: Vision Res Source Type: journals

Cell Penetrating Peptide POD Mediates Delivery of Recombinant Proteins to Retina, Cornea and Skin.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The objective of the current study was to examine whether biologically relevant macromolecules such as proteins, genetically fused with POD could also be delivered into retinal tissues in vivo. We generated a POD-GFP fusion protein and examined its cell and tissue penetrating properties. We found that endogenously expressed POD-GFP fusion protein localized to the nucleus, suggesting that POD acts as a nuclear localization signal. Adenovirus (Ad) vectors expressing POD-GFP fusion protein were constructed and the recombinant protein was purified from Ad-infected human embryonic retinoblasts (HER). Exogenously supplied POD-GF...
Source: Vision Research - September 1, 2009 Category: Opthalmology Authors: Johnson LN, Cashman SM, Read SP, Kumar-Singh R Tags: Vision Res Source Type: journals

Modeling Mechanisms of Perceptual Learning with Augmented Hebbian Reweighting.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Using the external noise plus training paradigm, we have consistently found that two independent mechanisms, stimulus enhancement and external noise exclusion, support perceptual learning in a range of tasks. Here, we show that re-weighting of stable early sensory representations through Hebbian learning (Petrov, Dosher & Lu, 2005, 2006) can generate performance patterns that parallel a large range of empirical data: (1) perceptual learning reduced contrast thresholds at all levels of external noise in peripheral orientation identification (Dosher & Lu, 1998, 1999), (2) training with low noise exemplars transfe...
Source: Vision Research - August 31, 2009 Category: Opthalmology Authors: Lu ZL, Liu J, Dosher BA Tags: Vision Res Source Type: journals

Spatial-frequency tuning in the pooling of one- and two-dimensional motion signals.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We examined whether the narrow spatial-frequency tuning present at the local-motion level is preserved at the global-motion-pooling stage. Stimuli consisted of numerous drifting Gabor or plaid elements that were either signal (carrier drift-speed consistent with a given global-motion vector) or noise (drift speed consistent with a random, noise vector). The carrier spatial-frequencies of the signal and noise elements were independently varied. Regardless of the frequency of the signal elements, broad low-pass masking functions were obtained for both Gabor (one-dimensional) and Plaid (two-dimensional) conditions when measur...
Source: Vision Research - August 31, 2009 Category: Opthalmology Authors: Amano K, Edwards M, Badcock DR, Nishida S Tags: Vision Res Source Type: journals