Resident Physician Neurosurgery, University of Southern California Los Angeles, California, United States
Introduction: The human amygdala is classically thought to be involved in emotional and fear responses, but little is known about its role in motor processing. We have previously shown that the amygdala exhibits gamma-band modulation during motor execution. Like the gamma-band, the beta-band (13-30 Hz) is important in movement processing, and we have shown previously that in the presence of movement uncertainty, beta-band modulation occurs in the hippocampus. In this study we sought to compare baseline levels of beta-band power in the human amygdala between a Direct Reach and a Go/No-Go task -- a measure of movement uncertainty.
Methods: Nine patients with medically refractory epilepsy underwent stereo electroencephalography for seizure localization with electrodes in the amygdala on the left only (2/9), right only (2/9), or bilaterally (5/9). Patients performed a Direct Reach task in which they were prompted to reach to a target, and they performed a Go/No-Go task in which they were prompted either to reach or not reach. Trial averaged beta-band power was computed during the fixation (baseline) phases the Direct Reach and the Go/No-Go tasks, and means were compared. Statistical significance was computed with a Wilcoxon signed-rank test with a cutoff of p< 0.05.
Results: In seven patients with left-sided contacts, five patients (71%) had an increase in beta-band power (3 of which were statistically significant) when comparing the fixation phase of the Go/No-Go task with that of the Direct reach task. In the seven patients with right-sided contacts, four patients (57%) had an increase in beta-band power (2/4 statistically significant).
Conclusion : In this study, we demonstrated that there is a tendency to an increase in baseline beta-band power in a Go/No-Go task when compared to a Direct Reach task. Further studies should aim to further define the role of beta-band modulation in the amygdala in movement uncertainty.
