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Results 501 - 550 of 1565
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Jordan Heather - - 2006
Human observers adapted to complex biological motions that distinguish males from females: viewing the gait of one gender biased judgments of subsequent gaits toward the opposite gender. This adaptation was not simply due to local features of the stimuli but instead relied upon the global motion of the figures. These ...
Sillito Adam M - - 2006
Feedback projections are an integral part of the mammalian visual system. Although it is tempting to relegate them to a subsidiary role in visual processing, because their supposed latency and lag might appear to be unfavourable for an involvement in fast processing, this is a dangerous simplification. Certainly for the ...
Gomi Hiroaki - - 2006
In addition to the goal-directed preplanned control, which strongly governs reaching movements, another type of control mechanism is suggested by recent findings that arm movements are rapidly entrained by surrounding visual motion. It remains, however, controversial whether this rapid manual response is generated in a goal-oriented manner similarly to preplanned ...
Cowey Alan A Department of Experimental Psychology, University of Oxford, Oxford, OX1 3UD, UK. - - 2006
Several published single case studies reveal a double dissociation between the effects of brain damage in separate extra-striate cortical visual areas on the perception of global visual motion defined by a difference in luminance (first-order motion) versus motion defined by a difference in contrast (second-order motion). In particular, the medial ...
Beardsley Scott A SA Department of Biomedical Engineering, Marquette University, Milwaukee, WI, - - 2006
Successive stages of cortical processing encode increasingly more complex types of information. In the visual motion system this increasing complexity, complemented by an increase in spatial summation, has proven effective in characterizing the mechanisms mediating visual perception. Here we report psychophysical results from a motion-impaired stroke patient, WB, whose pattern ...
Berryhill Marian E - - 2006
Unlike saccades, smooth pursuit eye movements (SPEMs) are not under voluntary control and their initiation generally requires a moving visual target. However, there are various reports of limited smooth pursuit of the motion of a subject's own finger in total darkness (pursuit based on proprioceptive feedback) and to the combination ...
Hupfeld D - - 2006
Albino ferrets contrary to their pigmented conspecifics show no optokinetic nystagmus. Therefore, in this study motion perception was compared between pigmented and albino ferrets (Mustela putorius furo) trained to discriminate between coherently moving random dot patterns and dynamic noise stimuli in a two-alternative forced choice task. Fully coherently versus incoherently ...
Caplovitz G P - - 2006
The perceived angular velocity of an ellipse undergoing a constant rate of rotation will vary as its aspect ratio is changed. Specifically, a "fat" ellipse with a low aspect ratio will in general be perceived to rotate more slowly than a "thin" ellipse with a higher aspect ratio. Here we ...
Beintema J A - - 2006
The visual perception of human movement from sparse point-light walkers is often believed to rely on local motion analysis. We investigated the role of local motion in the perception of human walking, viewed from the side, in different tasks. The motion signal was manipulated by varying point lifetime. We found ...
Gerardin Peggy - - 2006
We tested whether motion and configural complexity affect perceived transparency. A series of five coherent chromatic transformations in color space was applied across a figure: translation, convergence, shear, divergence and rotation. The stimuli consisted of a bipartite or a checkerboard configuration (10 x 10 degrees), with a central static or ...
Siegel Markus - - 2007
A central goal in systems neuroscience is to understand how the brain encodes the intensity of sensory features. We used whole-head magnetoencephalography to investigate whether frequency-specific neuronal activity in the human visual cortex is systematically modulated by the intensity of an elementary sensory feature such as visual motion. Visual stimulation ...
Kreegipuu Kairi - - 2007
Manual reaction time (RT) and visual evoked potentials (VEP) were measured in motion onset and offset detection tasks. A considerable homology was observed between the temporal structure of RTs and VEP intervals, provided that the change in motion was detected as soon as the VEP signal has reached critical threshold ...
Bucher Kerstin - - 2006
Abilities to discriminate forms defined by motion continue to develop throughout childhood. To investigate late development of the visual motion system, we measured brain activity with event-related EEG potentials (ERPs) and functional magnetic resonance imaging (fMRI) in groups of adolescents (15-17 years) and adults (20-30 years) during a visual form ...
Troje Nikolaus F - - 2006
If biological-motion point-light displays are presented upside down, adequate perception is strongly impaired. Reminiscent of the inversion effect in face recognition, it has been suggested that the inversion effect in biological motion is due to impaired configural processing in a highly trained expert system. Here, we present data that are ...
Amano Kaoru - - 2006
To explore the timing and the underlying neural dynamics of visual perception, we analyzed the relationship between the manual reaction time (RT) to the onset of a visual stimulus and the time course of the evoked neural response simultaneously measured by magnetoencephalography (MEG). The visual stimuli were a transition from ...
Federspiel Andrea - - 2006
Previous studies on motion perception revealed motion-processing brain areas sensitive to changes in luminance and texture (low-level) and changes in salience (high-level). The present functional magnetic resonance imaging (fMRI) study focused on motion standstill. This phenomenon, occurring at fast presentation frequencies of visual moving objects that are perceived as static, ...
Nichols David F - - 2006
A two-level dynamical model of motion pattern formation is developed in which local motion/ nonmotion perceptual decisions are based on inhibitory competition between area V1 detectors responsive to motion-specifying versus motion-independent stimulus information, and pattern-level perceptual decisions are based on inhibitory competition between area MT motion detectors with orthogonal directional ...
Keshner E A - - 2006
We examined how spatial and temporal characteristics of the perception of self-motion, generated by constant velocity visual motion, was reflected in orientation of the head and whole body of young adults standing in a CAVE, a virtual environment that presents wide field of view stereo images with context and texture. ...
Shi Lei - - 2006
The extraction of the direction of motion from the time varying retinal images is one of the most basic tasks any visual system is confronted with. However, retinal images are severely corrupted by photon noise, in particular at low light levels, thus limiting the performance of motion detection mechanisms of ...
Slobounov Semyon - - 2006
Abnormal balance in individuals suffering from traumatic brain injury (TBI) has been documented in numerous recent studies. However, specific mechanisms causing balance deficits have not been systematically examined. This paper demonstrated the destabilizing effect of visual field motion, induced by virtual reality graphics in concussed individuals but not in normal ...
Hock Howard S - - 2006
The relationship between local-level motion detection and higher level pattern-forming mechanisms was investigated with the motion quartet, a bistable stimulus for which either horizontal or vertical motion patterns are perceived. Local-level perturbations in luminance contrast affected the stability of the perceived patterns and, thereby, the size of the pattern-level hysteresis ...
Delon-Martin Chantal - - 2006
The aim of this study was to compare the time course of motion-related source activities evoked by the onset of different kinds of visual motion stimuli in human subjects. Event-related potentials (ERP) were recorded from 64 scalp electrodes in ten healthy subjects while they were viewing four different types of ...
Durant Szonya - - 2006
Motion transparency, in which patterns of moving elements group together to give the impression of lacy overlapping surfaces, provides an important challenge to models of motion perception. It has been suggested that we perceive transparent motion when the shape of the velocity histogram of the stimulus is bimodal. To investigate ...
Peelen Marius V MV School of Psychology, University of Wales, Bangor, Gwynedd LL57 2AS, United Kingdom. - - 2006
Accurate perception of the actions and intentions of other people is essential for successful interactions in a social environment. Several cortical areas that support this process respond selectively in fMRI to static and dynamic displays of human bodies and faces. Here we apply pattern-analysis techniques to arrive at a new ...
Lange Joachim - - 2006
Biological motion perception is the compelling ability of the visual system to perceive complex human movements effortlessly and within a fraction of a second. Recent neuroimaging and neurophysiological studies have revealed that the visual perception of biological motion activates a widespread network of brain areas. The superior temporal sulcus has ...
Greenwood John A - - 2006
When transparent motion is defined purely by direction differences, observers fail to detect more than two signal directions simultaneously [Edwards, M., & Greenwood, J.A. (2005). The perception of motion transparency: A signal-to-noise limit. Vision Research, 45, 1877-1884]. This limit is strongly related to signal-detection thresholds for transparent motion, which are ...
Simmers A J - - 2006
Previously, we have shown that humans with amblyopia exhibit deficits for global motion discrimination that cannot be simply ascribed to a reduction in visibility or contrast sensitivity. Deficits exist in the processing of global motion in the fronto-parallel plane that suggest reduced extra-striate function (i.e., MT) in amblyopia. Here, we ...
Tadin Duje - - 2006
Center-surround interactions are a key property of visual motion mechanisms. Using a temporal reverse correlation method with human observers, we investigated perceptual interactions between a brief center motion (approximately 20 ms) and a surround that moved up-down with a new direction chosen randomly every 5 ms. The aim was to ...
Brooks A - - 2007
The processing of biological motion is a critical, everyday task performed with remarkable efficiency by human sensory systems. Interest in this ability has focused to a large extent on biological motion processing in the visual modality (see, for example, Cutting, J. E., Moore, C., & Morrison, R. (1988). Masking the ...
Kinsey Kristofer - - 2006
Several studies have indicated a key role for dorsal stream processing in lexical decoding. To examine this relationship further, performance on orthographic and phonological reading tests was compared with both steady-state visual evoked potentials and a putative behavioral measure of dorsal stream processing, coherent motion detection. Frequency analysis of the ...
Villeneuve M Y MY Laboratoire des Neurosciences de la Vision, Ecole d'optométrie, Université de Montréal, CP 6128, succ. Centre-ville, Montréal, QC, Canada, H3C - - 2006
In cats, the postero-medial part of lateral suprasylvian cortex (PMLS) is generally considered a key area for motion processing. While behavioral studies have indeed supported the role of PMLS cortex in higher order motion integration (Cereb Cortex 6:814-822, 1996), there is no evidence that individual PMLS cells can perform such ...
Sanabria Daniel - - 2007
Motion information available to different sensory modalities can interact at both perceptual and post-perceptual (i.e., decisional) stages of processing. However, to date, researchers have only been able to demonstrate the influence of one of these components at any given time, hence the relationship between them remains uncertain. We addressed the ...
Streepey Jefferson W - - 2007
We explored the destabilizing effect of visual field motion as the base of support (BOS) and the field of view (FOV) were narrowed. Visual field motion was achieved using an immersive virtual environment (scene) that moved realistically with head motion (natural motion) and translated sinusoidally at 0.1Hz in the fore-aft ...
Skottun Bernt C - - 2006
The suggestion that coherent motion may serve as a test of magnocellular sensitivity is problematic. However, the nature of the problems depends on how the "magnocellular system" is defined. If this term is limited to subcortical entities, the problems are that subcortical neurons are not directionally selective, and that their ...
Kavcic Voyko - - 2006
We assessed visual processing related to navigational impairment in Alzheimer's disease hypothesizing that visual motion evoked responses to optic flow simulating observer self-movement would be linked to navigational performance. Mild Alzheimer's disease and older adult control subjects underwent open-field navigational testing, visual motion perceptual threshold determination and a battery of ...
Royden Constance S - - 2006
Displays commonly used for testing heading judgments in the presence of rotations are ambiguous to observers. They can be interpreted equally well as motion in a straight line while rotating the eyes or as motion on a curved path. This has led to conflicting results from studies that use these ...
Lorteije Jeannette A M - - 2006
Viewing static photographs of objects in motion evokes higher fMRI activation in the human medial temporal complex (MT+) than looking at similar photographs without this implied motion. As MT+ is traditionally thought to be involved in motion perception (and not in form perception), this finding suggests feedback from object-recognition areas ...
Kumar T - - 2006
Experiments to determine the optimum conditions for perceiving illusory motion in Engima-like patterns have also demonstrated that the illusory motion is not the result of unintended motion of the image on the retina due to microsaccades or accommodative changes in the lens of the eye but instead has a cortical ...
Rodríguez Valia - - 2006
During transparent motion, attention to changes in the direction of one illusory surface will impede recognition of a similar event affecting the other surface if both are close together in time. This is a form of object-based attentional blink (AB). Here, we show that this AB is related to a ...
McKeefry D J - - 2006
Analysis of the colour and motion of objects is widely believed to take place within segregated processing pathways in the primate visual system. However, it is apparent that this segregation cannot remain absolute and that there must be some capacity for integration across these sub-modalities. In this study, we have ...
Kuhlmann Simone - - 2006
Biological-motion perception can be regarded as a template-matching process. We are concerned with the visual cues in this template. Biological-motion perception is usually studied with point-light displays similar to the point-light displays invented by Johansson (1973 Perception and Psychophysics 14 201 - 211). These stimuli are in some ways abstract. ...
Xiao Quan Q Columbia University, Department of Psychiatry, Center for Neurobiology and Behavior, David Mahoney Center for Brain and Behavior Research, New York, New York 10032, - - 2006
The visual responsiveness and spatial tuning of frontal eye field (FEF) neurons were determined using a delayed memory saccade task. Neurons with visual responses were then tested for direction selectivity using moving random dot patterns centered in the visual receptive field. The preferred axis of motion showed a significant tendency ...
Smith A T - - 2006
The macaque V5/MT complex comprises several sub-regions but little is known of their human homologues. We examined human V5/MT with fMRI in terms of specificity to optic flow stimuli, a key characteristic of macaque MST. Stimuli were large fields of moving dots, forming coherent global flow patterns. Random motion was ...
Wright W Geoffrey - - 2006
We evaluated the influence of moving visual scenes and knowledge of spatial and physical context on visually induced self-motion perception in an immersive virtual environment. A sinusoidal, vertically oscillating visual stimulus induced perceptions of self-motion that matched changes in visual acceleration. Subjects reported peaks of perceived self-motion in synchrony with ...
Calabro Finnegan J FJ Brain and Vision Research Laboratory, Department of Biomedical Engineering, Boston University, 44 Cummington Street, Boston, MA 02215, USA. - - 2006
Transparent motion stimuli allow us to investigate how visual motion is processed in the presence of multiple sources of information. We used stereo random-dot kinematograms to determine how motion processing is affected by the difference in direction and depth of two overlapping motion components. Observers judged whether a noise dot ...
Lange Joachim - - 2006
Biological motion perception is referred to as the ability to recognize a moving human figure from no more than a few moving point lights. Such point-light stimuli contain limited form information about the shape of the body and local image motion signals from the moving points. The contributions of form ...
Soto-Faraco Salvador - - 2006
Recent studies have highlighted the influence of multisensory integration mechanisms in the processing of motion information. One central issue in this research area concerns the extent to which the behavioral correlates of these effects can be attributed to late post-perceptual (i.e., response-related or decisional) processes rather than to perceptual mechanisms ...
Carter Elizabeth J EJ Duke University, Durham, NC 27708-0086, - - 2006
Prior studies have implicated the superior temporal sulcus region for processing various types of biological motion in children and adults. However, no previous research in children compared this activity to that involved in coherent, meaningful, non-biological motion perception to show specificity for biological motion processing. In this study, we used ...
Bidet-Ildei Christel - - 2006
We tested the ability of the mature visual system for discrimination between types of elliptic biological motion on the basis of event kinematics. Healthy adult volunteers were presented with point-light displays depicting elliptic motion when only a single dot, a moving point-light arm, or a whole point-light human figure was ...
Tse Peter Ulric - - 2006
Form analysis subserves motion processing in at least two ways: first, in terms of figural segmentation dedicated to solving the problem of figure-to-figure matching over time, and second, in terms of defining trackable features whose unambiguous motion signals can be generalized to ambiguously moving portions of an object. The former ...
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