Frans A. J. Verstraten

Bio: Frans A. J. Verstraten is an academic researcher from University of Sydney. The author has contributed to research in topics: Motion perception & Binocular rivalry. The author has an hindex of 34, co-authored 154 publications receiving 4365 citations. Previous affiliations of Frans A. J. Verstraten include F.C. Donders Centre for Cognitive Neuroimaging & Radboud University Nijmegen.

The motion aftereffect: A modern perspective.

Abstract: Motion perception lies at the heart of the scientific study of vision. The motion aftereffect (MAE), probably the best known phenomenon in the study of visual illusions, is the appearance of directional movement in a stationary object or scene after the viewer has been exposed to visual motion in the opposite direction. For example, after one has looked at a waterfall for a period of time, the scene beside the waterfall may appear to move upward when ones gaze is transferred to it. Although the phenomenon seems simple, research has revealed surprising complexities in the underlying mechanisms, and offered general lessons about how the brain processes visual information. In the last decade alone, more than 200 papers have been published on MAE, largely inspired by improved techniques for examining brain electrophysiology and by emerging new theories of motion perception. The contributors to this volume are all active researchers who have helped to shape the modern conception of MAE. Contributors: David Alais, Stuart Anstis, Patrick Cavanagh, Jody Culham, John Harris, Michelle Kwas, Timothy Ledgeway, George Mather, Bernard Moulden, Michael Niedeggen, Shin'ya Nishida, Allan Pantle, Robert Patterson, Jane Raymond, Michael Swanston, Peter Thompson, Frans Verstraten, Michael von Grunau, Nicolas Wade, Eugene Wist.

Time dilation in dynamic visual display

Abstract: How does the brain estimate time? This old question has led to many biological and psychological models of time perception (R. A. Block, 1989; P. Fraisse, 1963; J. Gibbon, 1977; D. L. I. Zakay, 1989). Because time cannot be directly measured at a given moment, it has been proposed that the brain estimates time based on the number of changes in an event (S. W. Brown, 1995; P. Fraisse, 1963; W. D. Poynter, 1989). Consistent with this idea, dynamic visual stimuli are known to lengthen perceived time (J. F. Brown, 1931; S. Goldstone & W. T. Lhamon, 1974; W. T. Lhamon & S. Goldstone, 1974, C. O. Z. Roelofs & W. P. C. Zeeman, 1951). However, the kind of information that constitutes the basis for time perception remains unresolved. Here, we show that the temporal frequency of a stimulus serves as the "clock" for perceived duration. Other aspects of changes, such as speed or coherence, were found to be inconsequential. Time dilation saturated at a temporal frequency of 4-8 Hz. These results suggest that the clock governing perceived time has its basis at early processing stages. The possible links between models of time perception and neurophysiological functions of early visual areas are discussed.

Parieto-Frontal Connectivity during Visually Guided Grasping

Abstract: Grasping an object requires processing visuospatial information about the extrinsic features (spatial location) and intrinsic features (size, shape, orientation) of the object. Accordingly, manual prehension has been subdivided into a reach component, guiding the hand toward the object on the basis of its extrinsic features, and a grasp component, preshaping the fingers around the center of mass of the object on the basis of its intrinsic features. In neural terms, this distinction has been linked to a dedicated dorsomedial "reaching" circuit and a dorsolateral "grasping" circuit that process extrinsic and intrinsic features, linking occipital areas via parietal regions with the dorsal and ventral premotor cortex, respectively. We have tested an alternative possibility, namely that the relative contribution of the two circuits is related to the degree of on-line control required by the prehension movement. We used dynamic causal modeling of functional magnetic resonance imaging time series to assess how parieto-frontal connectivity is modulated by planning and executing prehension movements toward objects of different size and width. This experimental manipulation evoked different movements, with different planning and execution phases for the different objects. Crucially, grasping large objects increased inter-regional couplings within the dorsomedial circuit, whereas grasping small objects increased the effective connectivity of a mainly dorsolateral circuit, with a degree of overlap between these circuits. These results argue against the presence of dedicated cerebral circuits for reaching and grasping, suggesting that the contributions of the dorsolateral and the dorsomedial circuits are a function of the degree of on-line control required by the movement.

What we can do and what we cannot do with fMRI

Abstract: Functional magnetic resonance imaging (fMRI) is currently the mainstay of neuroimaging in cognitive neuroscience. Advances in scanner technology, image acquisition protocols, experimental design, and analysis methods promise to push forward fMRI from mere cartography to the true study of brain organization. However, fundamental questions concerning the interpretation of fMRI data abound, as the conclusions drawn often ignore the actual limitations of the methodology. Here I give an overview of the current state of fMRI, and draw on neuroimaging and physiological data to present the current understanding of the haemodynamic signals and the constraints they impose on neuroimaging data interpretation.

Functional and effective connectivity: a review.

Abstract: Over the past 20 years, neuroimaging has become a predominant technique in systems neuroscience. One might envisage that over the next 20 years the neuroimaging of distributed processing and connectivity will play a major role in disclosing the brain's functional architecture and operational principles. The inception of this journal has been foreshadowed by an ever-increasing number of publications on functional connectivity, causal modeling, connectomics, and multivariate analyses of distributed patterns of brain responses. I accepted the invitation to write this review with great pleasure and hope to celebrate and critique the achievements to date, while addressing the challenges ahead.

An Introduction To The Event Related Potential Technique

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