Fig. 8.

Relation between corticocortical and intrathalamic synchronization. Responses were recorded simultaneously from four separate sites, two in the left A17 and two in the left LGN lamina A1 (top left inset). Drifting gratings with an orientation intermediate to the optimal orientation of the cortical neurons (top right inset) induce strong and stable corticocortical synchronization at a frequency of 33 Hz and a phase shift of 0.8 msec (cross-correlation function, top left panel). The sliding window cross-correlation (analysis window, 250 msec; step, 50 msec) shows that synchronous oscillations do not decay over time (top right panel). In contrast, intrageniculate synchronization occurs only during the initial response epoch (middle panels). There is no significant correlation between the responses of cortical and LGN neurons (bottom panels), indicating that cortical synchronization is independent of oscillatory LGN input. Average cross-correlation functions were computed from the 1000 msec window indicated in the right panels.