We are interested in understanding the neural and circuit basis of visual behavior, including visual processing, visuomotor behavior, visual decision-making, and visual learning. For example, how is visual information processed by specific components in the neural circuit to generate specific visual perception/motor behavior? How do sensory experience and behavioral context influence neural computation to guide adaptive behavior? Using the mouse model, we address these questions by studying several brain regions important for visual behavior: visual cortex, posterior parietal cortex, orbitofrontal cortex, and superior colliculus. Our techniques include multi-electrode recordings, in vivo and in vitro whole-cell patch recordings, optogenetic/pharmacogenetic manipulation, immunohistochemistry, and mouse visual behavior.
Neural mechanism contributing to figure-ground segregation
Neurons in the primary visual cortex (V1) often exhibit surround suppression, in which visual stimulation beyond a neuron's receptive field (RF) can reduce the neuron's response to RF stimulation. Surround suppression is suggested to contribute to the perceptual phenomenon of figure-ground segregation. Recent studies have shown that the degree of surround suppression is influenced by the activities of specific types of inhibitory neurons, which are in turn modulated by the brain state. Using the optogenetic approach, we are now studying how the tuning properties of V1 surround suppression are influenced by the activities of inhibitory neurons and cholinergic innervation in V1. We also study how visual behavior of figure-ground segregation is influenced by the activities of inhibitory neurons or cholinergic neurons.
Neural circuit mechanism contributing to visual learning behavior
During associative learning, humans and animals need to update the representation of environmental cues associated with desired outcomes. As part of the prefrontal cortex, orbitofrontal cortex (OFC) plays an important role in a variety of complex functions, such as reward coding, decision making, and flexible behavior. OFC lesions caused deficit in reversal learning, and pharmacological inactivation of OFC or ventral tegmental area (VTA) disrupted learning driven by unexpected outcomes, suggesting that the interaction of OFC and VTA is critical in associative learning. Given that OFC also provides feedback projections to sensory cortices (including visual cortex, auditory cortex, and somatosensory cortex), we hypothesize that OFC is involved in dynamic representation of reward-relevant visual stimuli through the interaction between OFC and visual cortex under the guidance of VTA prediction error signal. To test this hypothesis, we are studying (1) How does the feedback projection from OFC to V1 modulate the visual responses of V1 neurons and what is the local circuit mechanism underlying this modulation? (2) What is the circuit mechanism by which VTA dopamine neurons modulate the activity of V1-projecting OFC neurons? (3) How does manipulation of OFC to V1 projection or VTA to OFC projection influence visual learning behavior in mice?
Neural circuit mechanism contributing to visually-guided choice behavior
Studies in primates point out that sensory-guided choice behavior involves neural computations in several interconnected brain regions, including prefrontal cortex, parietal cortex, and superior colliculus. However, the contribution of specific cell types in each region to specific behavioral process, and the functional connectivity among these brain regions, remain unclear. We have established several visually-guided spatial choice paradigms in the mouse. To understand the circuit mechanism contributing to visually-guided choice behavior, we will perform chronic recordings and manipulations of specific cell type/connection in brain regions including the posterior parietal cortex and superior colliculus.