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  • Feedforward and Feedback Interactions for Visual Perception and Awareness

    报告人:Pieter R. Roelfsema, MD, PhD
    Netherlands Institute for Neuroscience, Amsterdam

    报告时间:2019年1月7日(周一) 14:00-16:00

    报告地点:京师学堂第三会议室

    报告人简介:
        Pieter R. Roelfsema received his MD degree in 1991. He did his PhD project with Wolf Singer at the Max-Planck-Institute for Brain Research in Frankfurt and he received his PhD degree in 1995. In 2002, he started to work at the Netherlands Institute for Neuroscience in Amsterdam where he became director in 2007. He is professor at the Free University of Amsterdam and also Professor at the AMC in Amsterdam. He received a NWO-VICI award (2008) and an ERC-Advanced grant (2013). Roelfsema studies visual perception, plasticity and memory in the visual system of experimental animals, humans, and with neural networks. His main question is how neurons in different brain areas work together during thinking. Even the simplest task activates thousands of neurons across a large number of cortical and subcortical brain areas. Roelfsema studies how these networks of neurons work together to solve the task and how they configure themselves during learning. He uses knowledge about the visual system to create a visual prosthesis for blind people that will restore a rudimentary form of sight.

    报告摘要:
        Most theories hold that early visual cortex is responsible for the local analysis of simple features while cognitive processes take place in higher areas of the parietal and frontal cortex. However, these theories are not undisputed because there are findings that implicate early visual cortex in visual cognition - in tasks where subjects reason about what they see. Are these cognitive effects in early visual cortex an epiphenomenon or are they functionally relevant for these mental operations? I will discuss new evidence supporting the hypothesis that the modulation of activity in early visual areas has a causal role in cognition. I will discuss how the modulation emerges as the interaction between brain areas, with a special role for specific classes of interneurons. The modulatory influences allow the early visual cortex to act as a multiscale cognitive blackboard for read and write operations by higher visual areas, which can thereby efficiently exchange information.

        I will next address how conscious access emerges. Along the cortical hierarchy, a progressively larger proportion of cells modulate their spiking activity according to the subject’s perceptual state, and the global workspace theory holds that stimuli only reach awareness and can be reported as soon as they induce a special, “ignited” state in frontal cortex. We found that stimuli reaching awareness indeed elicited a characteristic, ignited state. We could predict whether a weak stimulus reaches awareness based on the pre-stimulus brain state. Our findings provide new insights into the conditions that permit visual stimuli to enter into consciousness. They inspire new approaches to create a visual prosthesis for the blind, by direct interfacing with the visual cortex.