Changes in variance of neuronal signals may be perceptually relevant for stereo vision

We measured the variance/mean (v/m) ratio of neuronal firing rates in visual areas V1, V2 and V5/MT in response to correlated and anti-correlated random dot stereograms. Disparity-selective neurons in early visual areas V1 and V2 showed no significant difference in v/m ratios to the two types of stereo-stimuli, but neurons in area V5/MT had a significantly greater v/m ratio for anti-correlated compared to correlated stimuli. These results demonstrate that neurons in a visual area higher in the cortical hierarchy have a greater response variability to anti-correlated stimuli, which do not give rise to a coherent stereo percept. A recurrent cortical network including V5/MT that quenches neural variability may contribute to solving the stereo correspondence problem.