We asked what property of the fear-evoked theta oscillation accounted for the enhancement in theta-gamma coupling during the CS+. We first tested whether enhanced theta power during the CS+ (p < 0.001, sign-rank; Figure S3D) explains the increased coupling. Although there was a direct correlation between theta power and theta phase-gamma power coupling (Figure S3E), it did not exclusively explain the CS+ evoked enhancement in modulation. Considering epochs where theta power fell within equal ranges for both the pretone and CS+ (defined as standard deviations from the pretone mean), theta-fast gamma coupling was enhanced in the CS+ compared to pretone (Figure 2F).
