Responses of cells in cat's area 17 to random dot patterns: influence of stimulus size

We have investigated both the response of cells in the striate cortex to a moving random dot pattern (visual noise) and the extent to which these responses depend on stimulus size. Cell receptive fields (RF) were classified according to the level of modulation of their response to sinusoidal gratings and the spatial arrangement of their ON and OFF regions. Our results indicate that most complex and simple cells respond to visual noise. The amplitude of these responses depend largely on the area of the visual field that was stimulated. Most cells were optimally activated when the noise covered a region much larger than the RF. Our results suggest that the area beyond the classical RF may contribute to the cells' responsiveness to noise.