Fig. 9.

Relation between extracellular unit discharges and local field potentials as detected from spike events. Spike-triggered averages of local field potentials were first computed at each individual electrode. These spike-triggered averages were then averaged to yield a single curve, shown here for various states.A, In wake states, individual spikes were correlated with the negativity of the local field potentials (LFPs,avg; 5506 spikes processed). B, A similar relation was obtained during REM sleep (LFPs,avg; 19491 spikes processed). C, During slow-wave sleep, the average LFP events corresponding to spikes consisted of a broad negative deflection, followed by a slow positive deflection (LFPs, avg; 34244 spikes processed; note different time scale). In all cases, the same analysis based on randomly shuffled spikes did not evidence any preferred pattern (Control).