Neural mechanisms of active visual perception
Vision is an active perceptual process by which we select behaviorally relevant stimuli for detailed inspection while ignoring distractors. Spatial attention and ballistic eye movements known as saccades are two key mechanisms that mediate this selection process. Spatial attention is the ability to deploy limited perceptual resources to focal regions of interest in the visual field, while saccades, which are executed 2-3 times every second, allow us to align high-acuity central vision with objects of interest.
Visual information is processed in a hierarchy of areas in the brain, which cumulatively make up about 30% of the neocortex. Neurons in these cortical areas process information about various attributes, such as shape, color, and motion, of objects in the visual scene. These neurons are embedded within a layered (or laminar) structure in the sensory neocortex. There are stereotypical patterns of anatomical connectivity in this layered cortical architecture and these connectivity motifs are shared across sensory modalities (audition, somatosensation, etc.) leading to the idea of a canonical information processing circuit. Information processing in these laminar cortical circuits is continuously modulated by attention and eye movements.
By studying the functional dynamics of these intricate layered circuits while animals are engaged in challenging visual tasks, we hope to discover fundamental principles of information flow through the cortex. This will ultimately help us understand disease conditions such as ADHD and schizophrenia in which information flow is disrupted. We use the non-human primate (rhesus macaque and marmoset) as a model system. We employ cutting-edge techniques in high-density laminar electrophysiology, advanced data analysis, and computational modeling to answer the following broad but inter-related questions:
What are the principles of hierarchical processing in the sensory neocortex?
How is information flow in the laminar cortical circuit modulated by spatial attention?
How are the laminar cortical dynamics modulated by eye movements?
How is visual information processing modulated by the presence of contextual stimuli?
Neural mechanisms of social cognition
Primates, including humans, live in complex social structures and engage in rich interactions with members of their own species. Current paradigms of investigating complex social cognition are limited in terms of their ecological validity or are fragmented in scope. To overcome these limitations, we have developed novel methodologies for the accurate 3D tracking of freely moving animals as they interact in controlled social environments. Combining these with state-of-the-art computational and wireless neural recording techniques allows us to rigorously quantify the behavioral dynamics of social networks and elucidate the underlying neural dynamics that support social behavior. This is a collaborative effort with the Chang & Jadi labs at Yale.