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Directional Influence between the Human Amygdala and Orbitofrontal Cortex at the Time of Decision-Making

Figure 5

Time-frequency spectral conditional Granger causality.

(A, B, C) Net CGC, computed on the interval −1 s to +2 s from stimulus onset and 5 Hz to 40 Hz for each subject. Net CGC is given by the CGC from amygdala-to-OFC minus the CGC from OFC-to-amygdala. The spectral density used to compute CGC was calculated using a sliding 300 ms window and a multitaper technique with a step size of 10 ms. (D, E, F) The contact-pair net direction of influence was analyzed between each of the amygdala-OFC pairs, and then aggregated over all of the amygdala-OFC contacts for each subject. A two-sided cluster-based permutation test was performed for each subject by random rearrangement of trials for each contact. The cluster suprathreshold maximum was identified over a (time, frequency) grid composed of 280 ms by 2.5 Hz tiles for a total of 154 frequency-time clusters. The FWER was controlled using the same method as described for time-frequency coherence, and non-significant clusters masked in an equivalent fashion. A one-sided cluster-based permutation test was also performed on the absolute OFC-to-amygdala CGC to establish its contribution to the net CGC. The red contours define the borders of the clusters, internal to which represents the areas statistically significantly greater than zero, with an internal maximum CGC of 0.010, 0.006, and 0.010 for panels D, E, and F respectively.

Figure 5