Figure 4: Granger causality analyses and PSI.

(a) Granger causality analyses demonstrated consistently stronger influence for the amygdala-to-hippocampus direction (top left) than for the hippocampus-to-amygdala direction (top right) when contrasting the aversive to the neutral condition. The red and blue solid lines represent the real data from aversive and neutral conditions±s.e.m., respectively. Dotted lines denote 99% confidence intervals for the null distribution. (b) PSI between the aversive and the neutral conditions calculated point-by-point across time using the low-frequency signal from the modulating channel (coloured in red) and high gamma signal from the modulated channel (coloured in blue). Dotted lines above the graph denote significant differences between the two signals (all P<0.01, permutation test), showing that low-frequency activity from amygdala precedes hippocampus gamma for the majority of the stimuli duration (bottom left). The PSI did not show a directional influence from the hippocampus to amygdala (bottom right).