A mechanism that explains both the shift in the negative peak of the STA as well as its onset before time 0. A, The LFP has an ongoing oscillation at 8 Hz and spikes tend to occur 25 ms before its negative peak. The STA of the reference electrode (black trace) shows the contribution of the spike (sharp Gaussian with an SD of 2 ms centered at 0) and of the 8 Hz rhythm. The degree of phase locking determines the relative magnitudes of the two sources (arbitrarily chosen to be 0.4 and 0.08 for the spike transient and alpha rhythm). These two sources fall off at different rates with distance (d), depending on the degree of synchronization in the spikes and phase consistency of the alpha rhythm (space constants arbitrarily chosen to be 0.3 and 3 mm for the spike transient and alpha rhythm). B, Same data as in A, but filtered between 3 and 90 Hz, which decreases the spike transient but not the alpha rhythm. C, Same as in A, filtered between 3 and 20 Hz. D, STA (filtered between 3 and 90 Hz) for which spikes occur 10 ms before the negative peak of the rhythm. The spike transient (before filtering) and the rhythm both have a magnitude of 0.1.