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Andrea Benucci, Robert A. Frazor, Matteo Carandini; Imaging pattern adaptation in primary visual cortex. Journal of Vision 2007;7(15):52. doi: 10.1167/7.15.52.
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Neurons in primary visual cortex (V1) are profoundly affected by prolonged exposure to a high-contrast pattern. This pattern adaptation has two main consequences: (1) a reduction in responsiveness in the neurons tuned for the adapting pattern (2) a repulsive shift in tuning curves of a broader class of neurons (Dragoi et al., 2000). We asked how these effects on individual neurons modify the responses of the overall population. We recorded responses in V1 of anesthetized cats using voltage sensitive dye imaging. We presented contrast-reversing gratings having random orientation (tests), preceded by a contrast-reversing grating with fixed orientation (adaptor). Population responses were computed by pooling the activity of pixels that shared the same orientation preference in the unadapted condition. Adaptation decreased the responses of all neurons, especially those whose preferred orientation matched the adapting orientation. In some experiments, population responses were skewed away from the adapting orientation, while in others they acquired a bimodal tendency with two peaks of activity, each to one side of the adapting orientation. We conclude that pattern adaptation profoundly modifies the profile of population activity in V1, and engages complex mechanisms whose action depends on a combination of test orientation, preferred orientation, and adaptor orientation.
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