Joint encoding of stimulus and decision in monkey primary visual cortex

Abstract

We investigated whether neurons in monkey primary visual cortex (V1) exhibit mixed selectivity for sensory input and behavioral choice. Parallel multisite spiking activity was recorded from area V1 of awake monkeys performing a delayed match-to-sample task. The monkeys had to make a forced choice decision of whether the test stimulus matched the preceding sample stimulus. The population responses evoked by the test stimulus contained information about both the identity of the stimulus and with some delay but before the onset of the motor response the forthcoming choice. The results of subspace identification analysis indicate that stimulus-specific and decision-related information coexists in separate subspaces of the high-dimensional population activity, and latency considerations suggest that the decision-related information is conveyed by top-down projections.

Dynamic fading memory and expectancy effects in the monkey primary visual cortex

“…As previously described ( 88 ), results presented here were obtained from two adult rhesus monkeys ( Macacca mulatta . Monkey 1: male, 11 kg, 12 y old.…”

“…As previously described ( 88 ), the stimuli were images of single isolated objects with transparent background. The visible region of the image was normalized to equal pixel intensity (0.5) and root-mean-square contrast (0.275) and covered the classical RF of the recorded multi-units.…”

“…As previously described ( 88 ), both monkeys were chronically implanted in the left hemisphere over V1 with a microdrive system (Gray Matter Research) which had 32 individually movable microelectrodes. Data acquisition was performed using the TDT system (Tucker-Davis Technologies, Alachua, FL, USA).…”

“…All decoding analyses were based on LDA classifiers. As previously described ( 88 ), firing rates across channels were treated as independent variables, i.e., predictors, with repeated measurements across trials. To test for stimulus-specificity, image identity was used as class label.…”