Towards the neuronal correlates of visual awareness

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DESCRIPTION (Provided by the applicant) Abstract: The brain, a physical system composed of neurons and synapses, can give rise to what seems to be the least physical property of all: consciousness. How this transformation takes place has preoccupied generations of clinicians and scientists. Advances in Neuroscience over the last several decades make it possible to enquire into the neural circuits responsible for consciousness. This proposal focuses on one particular aspect of conscious experience: the neuronal mechanisms and circuits that underlie visual awareness. We propose to study visual awareness using a combination of neurophysiology, psychophysics and electrical stimulation. We take advantage of a rare opportunity to examine activity in the human occipital and temporal lobes using neurophysiology at high spatial and temporal resolution (neurons and milliseconds) while subjects report their perceptions. We propose two experiments where visual perception is dissociated from the visual input: binocular rivalry and motion-induced blindness. In both cases, perception changes in spite of a constant visual input. We investigate where, when and how neuronal responses along ventral visual cortex (from primary visual cortex to inferior temporal cortex) change their activity patterns with the perceptual alternations. Furthermore, we ask whether those neurophysiological responses are sufficient to elicit perception by electrically stimulating local circuits. Impairments in conscious processing can be devastating and are at the core of seemingly diverse conditions as epilepsy, vegetative coma, schizophrenia and autism. Furthering our understanding of the link between brains and minds in the context of vision will pave the way for addressing other aspects of consciousness and may have profound implications in changing how we think about and address these challenging disorders. Public Health Relevance: The brain, a physical system composed of neurons and synapses, can give rise to what seems to be the least physical property of all: consciousness. Understanding the neuronal mechanisms that give rise to perceptions, feelings and thoughts is arguably one of the biggest scientific challenges today. Advances towards describing the link between neuronal activity and perception will have a profound impact in our society, particularly in clinical applications. There are multiple clinical conditions that involve altered states of consciousness including epilepsy, autism, vegetative coma and schizophrenia among others. Subjects afflicted by these conditions can live for years, yet their quality of life (and that of their surrounding friends and families) can be severely impaired. These conditions lead to social and learning challenges that often impact the afflicted individuals for life. At the intersection of these conditions resides a fundamental challenge to express conscious thoughts and to perceive conscious feelings. In all these cases, consciousness can be behaviorally defined. However, what, when and how brain activity leads to conscious experience is not understood. Here we specifically focus on visual awareness because it is easier to manipulate the visual input, we understand more about the underlying circuitry and we can quantitatively assess perception rather accurately. Our research efforts will investigate the types of neurons, locations, circuits, interactions and dynamics that give rise to visual perception.