Consistency of encoding in monkey visual cortex

Are different kinds of stimuli (for example, different classes of geometric images or naturalistic images) encoded differently by visual cortex, or ar e the principles of encoding the same for all stimuli? We examine two respo nse properties: (1) the range of spike counts that can be elicited from a n euron in epochs representative of short periods of fixation (up to 400 msec ), and (2) the relation between mean and variance of spike counts elicited by different stimuli, that together characterize the information processing capabilities of a neuron using the spike count code. In monkey primary vis ual cortex (V1) complex cells, we examine responses elicited by static stim uli of four kinds (photographic images, bars, gratings, and Walsh patterns) ; in area TE of inferior temporal cortex, we examine responses elicited by static stimuli in the sample, nonmatch, and match phases of a delayed match -to-sample task. In each area, the ranges of mean spike counts and the rela tion between mean and variance of spike counts elicited are sufficiently si milar across experimental conditions that information transmission is unaff ected by the differences across stimulus set or behavioral conditions [alth ough in 10 of 27 (37%) of the V1 neurons there are statistically significan t but small differences, the median difference in transmitted information f or these neurons was 0.9%]. Encoding therefore appears to be consistent acr oss experimental conditions for neurons in both V1 and TE, and downstream n eurons could decode all incoming signals using a single set of rules.