EVENT DETAILS AND ABSTRACT

Title: Modeling the function and development of a piece of the cerebral cortical circuit: Cat V1 layer 4
Speaker: Ken Miller
Speaker Info: University of California San Francisco
Brief Description:
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Abstract:

The primary visual cortex (V1) of the cat is perhaps the best- studied piece of the cerebral cortex. The cortical circuit is traditionally divided into six layers, with layer 4 specializing in receiving inputs from "lower" stations in the cortical hierarchy. In V1, layer 4 receives visual inputs from the lateral geniculate nucleus (LGN), which in turn receives the major output of the retina. Cells in LGN respond to light/dark edges but without distinction between edges of different orientations, whereas a given cell in layer 4 of V1 will respond only to a narrow range of orientations. The set of orientations to which a V1 cell will respond stays invariant under changes in stimulus magnitude or "contrast". Cells in LGN also respond well to fast-moving stimuli that do not activate V1 cells. We have developed a circuit model of layer 4 of V1 that accounts for a wide range of V1 response properties, including orientation preferences and their invariance under changes of stimulus contrast as well as speed preferences. Key to the model is a specific pattern of feedforward inhibition (LGN-driven, via cortical inhibitory interneurons) that counterbalances the direct LGN excitation. We show further that the model circuit will develop or "self-organize" from simple "Hebbian" rules of synaptic modification, under which the patterns of neural activity drive the modification of synapses.... CompleteAbstract