Cross-Correlation Study of Network Dynamics in the Cat Primary Visual Cortex

Abstract

To assess the network dynamics in the primary visual cortex, we performed simultaneous recordings of neuronal activity from cell pairs within 1 mm apart in anesthetized and paralyzed cats. Cross-correlograms (CCs) were calculated for the responses to grating stimuli with varying orientations and sizes for the 30 cell pairs to date. There were three patterns of cell pairs in respect of tuning property to stimulus sizes. First, both cells exhibited strong suppression of firings with stimuli larger than their classical receptive field (CRF). Second, only one cell exhibited suppression to the large stimuli while the other did not. In these two patterns, the contribution of the peak CCs became smaller when the grating stimulus was larger than the CRFs. And third, both cells did not significantly reduce activity to the grating patch larger than their CRFs. In this case, the peak contribution in CCs did not vary with an increase of the stimulus size. We concluded that the strength of firing interaction is positively correlated with the change in firing rate of cell pairs because of the change of stimulus sizes. We also analyzed CCs in respect of orientation preference of cell pairs. Although the significant peak CCs were most often observed for the common and optimal orientation of the cell pairs, there were some pairs that showed strong peaks for the nonpreferred orientation (more than 60° apart from the optimal) of stimulus, which evoked responses with low firing levels. This result suggests that the strength of firing correlation of cell pairs does not simply depend on the firing rate when the stimulus orientation is varied.