SYNCHRONOUS HIGH-FREQUENCY OSCILLATIONS IN CAT AREA-18

The present study extends knowledge of the basic properties of correla ted oscillatory activity patterns in the visual cortex of anaesthetize d cats. Recordings with multiple electrodes were performed in area 18 and the correlations of multi-unit activity in the frequency range 35- 80 Hz were determined using the coherence function, Statistical analys is revealed that the multi-unit correlations depended on the cortical distance between the recording sites, the orientation selectivity of t he neurons and their cortical layer. On average, correlations dropped to chance level within several millimetres and were higher in lower th an in upper cortical layers, Similar results were found by analysing t he correlations of oscillatory patterns in local field potentials reco rded from the same electrodes. Correlations of neurons with similar or ientation preferences were higher than those of neurons with different orientation preferences. Comparison to a matched sample from area 17 st-cowed that the correlations in areas 18 and 17 depended on similar properties of the neurons. The dependences of correlated oscillations resembled the known pattern and specificity of intra-areal fibre conne ctions, suggesting that the correlations were intracortically establis hed, Since correlations were specifically and not randomly related to the response properties of cortical neurons and were prominent in a vi sual area other than area 17, the findings suggest that correlated osc illatory activity provides a potential neural code supporting sensory information processing.