Beta-band modulation in the human hippocampus during a conflict response task

Objective. Identify the role of beta-band (13-30 Hz) power modulation in the human hippocampus during conflict processing.Approach. We investigated changes in the spectral power of the beta band (13-30 Hz) as measured by depth electrode leads in the hippocampus during a modified Stroop task in six patients with medically refractory epilepsy. Previous work done with direct electrophysiological recordings in humans has shown hippocampal theta-band (3-8 Hz) modulation during conflict processing. Local field potentials sampled at 2 k Hz were used for analysis and a non-parametric cluster-permutationt-test was used to identify the time period and frequency ranges of significant power change during cue processing (i.e. post-stimulus, pre-response).Main results. In five of the six patients, we observe a statistically significant increase in hippocampal beta-band power during successful conflict processing in the incongruent trial condition (cluster-based correction for multiple comparisons,p< 0.05). There was no significant beta-band power change observed during the cue-processing period of the congruent condition in the hippocampus of these patients.Significance. The beta-power changes during conflict processing represented here are consistent with previous studies suggesting that the hippocampus plays a role in conflict processing, but it is the first time that the beta band has been shown to be involved in humans with direct electrophysiological evidence. We propose that beta-band modulation plays a role in successful conflict detection and automatic response inhibition in the human hippocampus as studied during a conflict response task.