CAREER: Large-scale brain dynamics underlying visual perceptual awareness

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Despite the enormous progress in neuroscience over the past century, the neurobiological basis of our subjective awareness remains a mystery. Advances over the past decades have now enabled one major component of this question to be rigorously addressed by modern neuroscientific tools. That is, how does the brain give rise to perceptual awareness of sensory stimuli? In particular, there has been a concerted effort by neuroscientists and psychologists to unravel the neural bases of visual perceptual awareness. Currently, one major open question is whether regions in the human frontal cortex directly contribute to the content of visual perceptual awareness or, alternatively, are only involved in the maintenance and manipulation of perceptual information represented in posterior visual cortices. With the support of this NSF CAREER award, Dr. Biyu He will address this question and develop a framework for understanding large-scale brain dynamics underlying visual perceptual awareness. To this end, the project combines visual psychophysics, state-of-the-art multimodal human brain imaging, noninvasive brain stimulation and computational modeling. The outcome of this work will lead to a better understanding of the biological basis of human perceptual awareness in both normative and clinical populations. The educational activities supported by this award are intended to stimulate scientific interest and enthusiasm in neuroscience in student populations, and increase the use of computational neuroscience and state-of-the-art multimodal imaging tools in human neuroscience research. The research objective of this proposal is to tackle a central question in neuroscience: How does the brain give rise to perceptual awareness of sensory stimuli? To investigate this question, the research group will combine psychophysics, multi-modal brain imaging, and noninvasive brain stimulation in humans, facilitated by computational modeling, and use vision as the model system. Specifically, the following questions are addressed: 1) Do neural activities in frontal regions contribute to perceptual content when stimulus ambiguity must be resolved? 2) Do neural activities in frontal regions contribute to gating the access to awareness by a particular piece of visual information? The central hypothesis is that large-scale brain activity during conscious visual perception exhibits initial-state-dependent, robust, transient dynamics shaped by the interactions between frontal and visual cortices. The experimental approach features recording of brain activity at whole-brain and large-scale network levels using a combination of ultra-high-field (7 Tesla) functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG), and electrocorticography (ECoG) to leverage the high spatial or high temporal resolution of each modality, and to further manipulate brain activity using high-definition transcranial direct current stimulation (HD-tDCS). These studies will have a major impact for understanding how brain systems coordinate to generate perceptual awareness of environmental input.