Figure 3

Rapid time course of learning effects on theta nested gamma. Pseudocolor panels show changes in: (A) Theta amplitude, (B) Theta/gamma ratio and (C) Coherence between theta phase and gamma amplitude in the right IT during the learning of one new face pair in Sheep B over sequential (top to bottom) blocks of 20 trials conducted over approximately a 20 min period (data plotted from 60 electrodes). Discrimination performance in each of the 4 blocks is shown on the left hand side (i.e. the learning criterion of > 80% correct was achieved in the second block of 20 trials and in subsequent blocks). The face pair stimulus occurs at time zero and the pseudocolor scale indicates normalised (by the maximum value during the stimulus) differences between pre and during stimulus. It can be seen that increased theta amplitude and the theta/gamma ratio occur in blocks of trials where the learning criterion is achieved. Theta-gamma coupling also increases across the gamma range but most notably at 6 and 8 Hz in the theta range.