Figure 1

Theta-gamma coupling in IT. (A) shows a typical example of coupling between theta phase and gamma amplitude taken from Sheep B (session 110305-1, channel 3) for the pre-stimulus (left) and during-stimulus (right) periods before (left) and during (right) presentation of a learned stimulus pair. There is a clear increase in coherence (represented by pseudocolor scale) across the entire gamma range and parts of the theta range (particularly at 8 Hz) and no evidence for coupling with gamma at phase frequencies immediately below or above the theta band. The red/yellow areas indicate where coupling between the two frequencies was significant (p < 0.001). (B) Shows typical data from 10 adjacent individual channels (from same sheep and recording session as in (A)) which exhibited significant (p < 0.001) coupling between theta phase and gamma amplitude across a 1 s before and a 1s period during stimulus presentation. Peaks in gamma amplitude (red) can clearly be seen across the electrodes during the majority of the theta cycles displayed. These data also illustrate the strong synchronization of theta phase across individual channels. Patterns of gamma amplitude changes are also very similar across the electrodes. (C) Shows an example of the strength of coupling between theta phase and gamma amplitude for a single channel across two theta cycles. It can be seen that there is consistently stronger locking at around 180 degrees in both cycles.