Amygdala theta-gamma PAC did not distinguish aversive from neutral blocks or improve band-power decoding in 9 patients

This offline analysis tested theta-gamma phase-amplitude coupling (PAC) in bipolar amygdala SEEG from 9 patients during alternating 24-s neutral and aversive video blocks. PAC was measured with the Tort modulation index using 4-8 Hz phase and either 30-45 Hz or 70-150 Hz amplitude, with 100 within-block circular-shift surrogates. Median block z exceeded 1.645 in 1 of 9 patients for 30-45 Hz amplitude and 2 of 9 for 70-150 Hz amplitude. PAC did not differ between block types (Wilcoxon p=1.00 and p=0.73; 4 of 9 patients had higher PAC in aversive blocks for each band). Leave-one-pair-out shrinkage LDA had mean pair accuracy 0.57 for PAC features (p=0.34), 0.78 for band-power features (p=0.047), and 0.75 for band power plus PAC (p=0.063). Adding PAC to band power changed accuracy by -0.028 (Wilcoxon p=0.63). PAC was clear in only a few patients; high values may reflect epileptic spikes, which were not removed. The study included 8 block pairs per patient, tested one frequency pair at a time, measured each MI over a full 24-s block, and used offline analysis. The available compute limits prevented testing other phase bands or spike removal.

amygdala · intracranial EEG · phase-amplitude coupling · theta-gamma coupling · emotion · aversive stimuli · band power · LDA · brain-computer interface