The Gilbert laboratory studies the primary visual cortex, a credit card-sized region of cells at the back of the brain and the site of the initial stage of cortical processing of information. The job of the visual cortex is to take signals coming from the retina, identify object contours and determine their shapes. The laboratory investigates the mechanism, at the level of cortical circuitry, by which this occurs. They discovered a plexus of long-range horizontal connections that mediate the assembly of contours and the parsing of visual scenes into objects and background. Using a combination of single-cell electrophysiological recordings, optical imaging of cortical functional architecture and multiphoton imaging of labeled cortical connections, Dr. Gilbert has found close correspondence between the geometry of these connections, the functional properties of visual cortical neurons and the perception of visual stimuli.

The laboratory also studies the way visual experience shapes the strategy by which the cortex analyzes sensory information, a process known as perceptual learning. They are interested in the contributions of different cortical areas along the visual pathway that facilitate this learning and are characterizing the functional changes at the level of individual neurons. The Gilbert laboratory has found that, even in adults, the visual cortex is capable of altering its functional properties and circuitry as a response to experiencing visual stimuli. These long-term changes aid in analyzing visual scenes as a result of normal visual experience, and play a role in functional recovery after damage of the central nervous system. In a series of experiments, Dr. Gilbert’s lab made permanent alterations to visual input of animals by creating retinal lesions. This procedure initially silences parts of the visual cortex, but over a period of weeks the cortex regains its ability to respond to visual stimuli. They found that the long-term changes involve axonal sprouting and synaptogenesis. The lab is studying the molecular mechanisms underlying cortical plasticity. Understanding adaptive changes in cortical functional architecture, circuitry and gene expression provides important insights into the mechanism of functional recovery after brain lesions and neurodegenerative disease, including macular degeneration.

The Gilbert lab has shown that the properties of the visual cortex reflect both sensory and behavioral contexts, suggesting that each cortical area is an adaptive processor that runs different programs according to the immediate demands of the perceptual task. Object recognition, for example, involves a countercurrent process of feedforward and feedback interactions. The top-down signal conveys information about attentional locus, perceptual task and object expectation. These results led to a novel view of cortical processing: Rather than having fixed functional properties, adult neurons are dynamically tuned, changing their specificities with varying sensory experience. Understanding the role of top-down interactions in sensory processing is likely to provide insight into behavioral disorders such as schizophrenia and autism, which have been suggested to be “disconnection syndromes,” or a dysfunction of top-down interactions between areas of the cerebral cortex. Based on these findings, Dr. Gilbert’s lab studies how neurons act as an interactive ensemble through computer models.

Dr. Gilbert and his colleagues use single-cell and optical recording while integrating molecular approaches with the systems-level analysis to understand the mechanisms of adult cortical plasticity. They study the circuitry and synaptic mechanisms underlying the dynamic changes in functional properties of cortical cells in behaving animals. They use electrophysiological recordings to study the more complex properties of cortical cells and their dependence on top-down influences and perceptual learning. Finally, they use human psychophysics to explore the perceptual consequences of dynamic changes in cortical properties.

CAREER

Dr. Gilbert received his M.D. and Ph.D. from Harvard Medical School in 1977, where he held an academic appointment until he joined Rockefeller in 1983 as assistant professor and head of laboratory. He became associate professor in 1985 and professor in 1991 and in 2004 was named Arthur and Janet Ross Professor. A member of the National Academy of Sciences and the American Academy of Arts and Sciences, he has received numerous awards, including the W. Alden Spencer Award from the Columbia University College of Physicians and Surgeons.