Suppression outside the classical cortical receptive field

The important visual stimulus parameters Fur a given cell are defined by th e classical receptive field (CRF). However, cells are also influenced by vi sual stimuli presented in areas surrounding the CRF. The experiments descri bed here were conducted to determine the incidence and nature of CRF surrou nd influences in the primary visual cortex. From extracellular recordings i n the cat's striate cortex, we find that for over half of the cells investi gated (56%, 153/271), the effect of stimulation in the surround of the CRF is to suppress the neuron's activity by at least 10% compared to the respon se to a grating presented within the CRF alone. For the remainder of the ce lls, the interactions were minimal and a few were of a facilitatory nature. In this paper, we focus on the suppressive interactions. Simple and comple x cell types exhibit equal incidences of surround suppression. Suppression is observed for cells in all layers, and its degree is strongly correlated between the two eyes for binocular neurons. These results show that surroun d suppression is a prevalent form of inhibition and may play an important t ote in visual processing.