Our research focuses on the functional organization and development of neural circuits in the cerebral cortex, the largest and most complex area of the brain, comprising 20 billion neurons and 60 trillion synapses–a neuronal network whose proper function is critical for sensory perception, motor control, and cognition. State of the art anatomical, electrophysiological, and imaging techniques are used to study neural circuits in primary visual cortex, an area where the emergence of novel response properties raises a host of tractable questions about the neural basis of visual perception. More broadly, the study of circuits in visual cortex provides a window into fundamental mechanisms of cortical processing that underlie a wide range of brain functions and serves as a model system for exploring the role of neural activity in the construction of cortical circuits.
Individual neurons in visual cortex have receptive fields that are responsive to small regions of visual space, and within this region, to specific properties of the visual stimulus such as the orientation of edges, their direction of motion, and color. Moreover, in species with well-developed visual capabilities, neurons exhibiting these properties are arrayed in a systematic fashion that reflects the underlying radial and tangential structure of cortical anatomy. Neurons with similar response properties are clustered together forming radial ‘columns’ that extend from the cortical surface to the white matter. Nearby columns generally have similar but slightly shifted stimulus preferences, an arrangement that results in orderly ‘maps’ of stimulus properties. Our research has played a pivotal role in defining the columnar architecture of cortical circuits and using this architecture as a functional referent to explore rules of intracortical connectivity, address questions of neural coding and behavior, and probe activity dependent mechanisms of cortical development.
Current studies in visual cortex employ in vivo 2-photon imaging, correlative light and electron microscopy, whole cell patch clamp recording, and targeted optogenetic stimulation to:
- Define the functional architecture of the synaptic inputs to the dendritic spines of individual cortical neurons
- Determine the functional organization of GABAergic neurons in visual cortex and their contribution to specific response properties
- Explore the early postnatal patterns of spontaneous neural activity in cortical circuits, follow their development over time, and determine their relation to the emergence of network representations of visual stimuli.
- Understand the changes in the response properties of cortical neurons that are responsible for the ability to learn fine visual discriminations