Cooperative filtering and transmission of visual information

We applied information-theoretic methods to multi-electrode array recordings in the primary visual cortex of cats to quantify the cooperation and temporal structure that arise in the responses of neural populations to drifting sinusoid gratings. The temporal structure and joint firing in these responses contributed information useful for discriminating small (<10o) orientation differences. The contributions from joint firing proportionally increased with larger populations of cells. We found that the independent firing rates of cells are adequate to represent coarse orientation differences (>10o). The orientation of a visual stimulus can determine the relative timing of the response onset across cells, which can modulate synchrony throughout the cortical circuit. Other structure in the responses, in the form of regularized interspike intervals, also depended on orientation and maintained multi-unit response coordination. The probabilities of the stimulus-dependent structures that we observed are substantial and far above chance. We conclude that cortical synchronization supports reliable propagation of visual information with high efficiency and that it carries greater precision and complexity of visual information than that available from average firing rates.