Bruno G. Breitmeyer, Ph.D. - US grants

Visual masking occurs when the visibility of one stimulus, called the target, is reduced by the presence of another stimulus, designated as the mask. Like the techniques of binocular rivalry and of multi-stable percepts of the same stimulus, visual masking provides a way to dissociate neural processes that are merely stimulus-dependent but not correlated with conscious perception, from neural processes that are percept-dependent and thus correlated with conscious perception of the stimulus. The broad long-term objective of this research is to use the visual masking paradigm to study the temporal dynamics in the micro-genesis of pattern processing from the time of stimulus presentation to the time of its full registration in consciousness. A modified dual-channel model of visual masking that incorporates mutual inhibitory interactions between sustained parvocellular (P) and transient magnocellular (M) pathways will be used to study how the cortical response evoked by the mask interacts with the early and late components of the cortical response evoked by the target. The project will rely on the masking paradigms of para- and metacontrast, theoretical tools based on neural-network modeling, and the additional psychophysical techniques of target disinhibition, binocular rivalry, and unconscious priming by a masked (perceptually suppressed) target. It will investigate where and when in the stream of processing the mechanisms implicated in suppression and disinhibition of target visibility are located. It will also probe whether and when the mechanisms implicated in suppression and disinhibition of target visibility relate to stimulus-dependent (unconscious) or percept-dependent (conscious) levels of neural processing. The research is expected to provide a better understanding of the perceptual processes leading to conscious registration of stimuli. The potential applications include the development of novel biomimetic engineering design principles for autonomous perceptual devices and the development of clinical diagnostic or vulnerability markers for disorders such as dyslexia and schizophrenia.

[unreadable] DESCRIPTION (provided by applicant): Recent research emphasis in neuroscience, neuropsychology and psychophysics on (a) the dynamics of visual information processing and (b) unconscious and conscious processing provide the framework for a much needed cross-disciplinary synthesis of the two themes. The workshop will cover a total of six relevant topics during the three-day period: 1) conceptual issues in studying conscious and unconscious visual processes, 2) neurophysiological correlates of dynamic processing in vision, 3) visual masking as a probe into the dynamics of vision, 4) temporal aspects of attention, 5) temporal characteristics of object and feature perception, and 6) the dynamic relation of unconscious and conscious processes in vision. Eighteen internationally prominent researchers, among them, neuroscientists, neuropsychologists, clinical psychologists, perceptual psychophysicists and computational neural-net modelers will be the speakers. Another 20 participants will be recruited from graduate students, postdoctoral fellows and junior faculty from underrepresented groups or institutions with limited resources in order to provide them the opportunity to interact with senior researchers. The workshop will be held at the University of Houston from November 1 through November 3, 2003. [unreadable] [unreadable]