Beta-band power modulation in the human amygdala during a Direct Reach arm reaching task

Abstract

The human amygdala is primarily known for its involvement in processing emotional and fearful responses, but newer evidence has identified a role for this structure in motor processing. Our lab previously utilized an arm-reaching task and observed significant beta-band (13-30 Hz) modulation in the hippocampus. Given these results, we sought to characterize the role of beta-band modulation in the amygdala during movement execution in participants with stereoelectroencephalography (SEEG) depth electrodes in the amygdala for seizure localization. We show that 9 of 13 participants (69.2 %) showed decreased beta-band power in the amygdala during the Response (movement execution) phase of an arm-reaching task when compared to Fixation (baseline). Secondary analyses show that there are no statistically significant differences in beta-band modulation between ipsilateral and contralateral implanted electrodes, but there is a small difference between male and female participants. The decrease in beta-band power in the amygdala during the Response phase of a Direct Reach task is consistent with our previous findings in the hippocampus. Our study is the first to report beta-band modulation in the amygdala during motor processing and sets the stage for further studies into the involvement of the amygdala in motor control.

Keywords: Amygdala; Beta-band power; Center-out arm reach task; Local field potential (LFP); Non-emotional motor processing; Stereoelectroencephalography (SEEG).

Fig. 1.

Preoperative T1-weighted MR images fused to postoperative CT scan showing lead placement in the amygdala bilaterally. A) coronal image and B) axial image.

Fig. 2.

Task design for the ‘center-out’ Direct Reach task. A) In the ITI, the participant waits for the fixation dot to appear (1–2 s), in the Fixation phase (1–4 s), the participant points to the fixation dot, and in the Response phase, the participant reaches for the target and double taps the screen, B) Targets appear at 1 of 8 random locations around fixation dot, and each number is displayed an equal number of times.

Fig. 3.

Representative single-trial ITI-to-ITI local field potential (LFP) tracing (top) and spectrogram (bottom) for a trial in which beta-band power decreases in the Response phase compared to the Fixation phase. Both plots are aligned with the ITI, Fixation, and Response phases of the trial.

Fig. 4.

Beta-band power decreases in the amygdala during the Response phase (RES) compared to the Fixation phase (FIX). A) Trial-averaged power spectral density (PSD) plot from a gray matter electrode contact in the amygdala in a representative participant, shaded regions represent the boot-strapped (n = 10,000) 95 % confidence intervals. B) Half-histogram/half-violin paired observation plot of trial-averaged power calculated over the frequency of significant modulation as determined by the nonparametric cluster-based permutation test (n = 1000, p < 0.05) for a representative gray matter electrode contact, gray lines represent individual trials in the 3 phases.