Neuroscience Program

Stephen Van Hooser

Associate Professor of Biology

Research Description

Development and function of cortical circuits

A fundamental mystery of brain science is to understand how networks of neurons assemble during development and function in circuits to enable perception and behavior. Unraveling this mystery requires an understanding of the relationships between the cellular-level properties of circuits -- the anatomical "wiring diagram" of connectivity on the one hand, and the functional properties of single neurons and synapses on the other -- and the systems-level properties such as sensory responses or motor outputs.

In the Neural Circuits Lab, we apply a new generation of optical and optogenetic tools to observe both fine-scale circuit features and systems-level responses at the same time, in the living brain. We combine these optical approaches with advanced physiological and anatomical techniques to address previously inaccessible questions about neural circuitry and its development in mammalian visual cortex.

Our current research is focused on 2 themes:

1. The role of experience in the development and maturation of neural circuits

   As a postdoc in David Fitzpatrick's lab at Duke, my colleagues and I identified a fertile model system for exploring the impact of experience on the development of neural circuits using ferret visual cortex, where motion selectivity develops in an experience-dependent manner. At the time of eye opening, cortical neurons exhibit orientation selectivity but they respond equally to stimulation in either of two opposite directions of motion. In the weeks after eye opening, most neurons develop a strong preference for motion in a single direction. We are interested in understanding whether experience merely permits the completion of developmental programs that are fully seeded prior to visual experience, or rather if experience alters the trajectory of circuit construction. In addition, we would like to understand which circuit elements are modified by experience and the learning rules that govern these changes.

2. Operating principles of cortical circuits

   Owing to 50 years of intense research, the field of neuroscience probably knows more about sensory response properties, functional architecture, and anatomical connections in primary visual cortex than in any other mammalian brain structure. While progress has been made towards understanding some of the circuit mechanisms underlying these receptive field properties, many fundamental circuit mechanisms have remained out of experimental reach. Do large neural circuits operate using feed forward or recurrent processing? How do cells maintain selectivity as signal strength changes? Is there a common functional plan for cortical circuits, or has evolution crafted unique circuits for each species and cortical region (see Van Hooser, 2007).