The role of correlations in orientation and contrast coding in the primary visual cortex

F. MONTANI, A. KOHN AND S. R. SCHULTZ

Santander, España

Workshop; Complex Systems: New Trends and Expectations; 2006

Spikes fired by nearby neurons are often correlated, but the significance of this correlation for perception is unclear. To evaluate the effect of correlation on the population coding of sensory information, we recorded responses of pairs of single neurons in primary visual cortex (V1) of the anaesthetized macaque monkey to stimuli of varying orientation and contrast. Both correlation of trial-to-trial variability and synchrony were found to depend on both stimulus orientation and contrast (Kohn and Smith 2005). We used information theory to examine whether this stimulus-dependent correlation could contribute to the neural coding orientation and contrast by pairs of V1 cells. We computed mutual information using the Nemenman-Shafee-Bialek estimation   (Nemenman et al 2004), and compared the ensemble information available from the pairs of cells with a spike pooling code, and with the sum of the single cell information values. This allowed to asses the degree of synergy (or conversely redundancy) in the coding.