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Adaptation of responses to prolonged stimulation in single neurons in area 17 of the cat Marlin, Stuart Graham


The locus and mechanisms of adaptation of neurons in Area 17 of the cat were investigated with extracellular unit recording techniques. Following prolonged visual stimulation, the responses of cells in Area 17 were reduced. The adaptation-induced changes in the responsivity of neurons could be restricted to small regions of the cell's receptive field and could show adaptation effects which spread asymmetrically across the receptive field. Prolonged unidirectional motion resulted in changes in the excitatory and inhibitory interactions between receptive field positions. These changes are thought to underlie the adaptation-induced changes in direction selectivity in cortical cells. The adaptation was not reduced by pharmacological agents which block the inhibitory neurotransmitter gamma-aminobutyric acid. Neurons in the lateral geniculate nucleus did not show adaptation at rates of stimulation which were optimal for inducing adaptation in cortical neurons. These experiments demonstrate that the adaptation of responses observed in visual cortical cells is not due to a general process which affects the responsivity of the cell, nor is adaptation the product of a GABAergic inhibitory input onto the cell. Rather adaptation must be a process occuring locally in either the pre or postsynaptic terminal or distal dendrites.

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