Beta-band desynchronization in the human hippocampus during movement preparation in a delayed reach task

Though the hippocampus is known for its role in memory and navigation, growing evidence has suggested that it is involved in voluntary movement. By investigating whether the hippocampus is active during movement preparation, we can understand its role in motor control. In this study, we utilized a Delayed Reach task to measure beta-band (13-30 Hz) amplitude changes in the human hippocampus during movement preparation. We hypothesized to observe beta-band event-related desynchronization (ERD) during the movement preparation phases. Eleven patients diagnosed with drug-resistant epilepsy were implanted with stereoelectroencephalographic (SEEG) depth electrodes and SEEG signals were recorded. We pre-processed the raw neural signals using the zap-line noise removal technique and re-referenced the data using a novel weighted electrode shaft re-referencing technique. The beta-band Power Spectral Density (PSD) was calculated using multi-taper spectral analysis and trial averaged PSD between task phases was compared using a cluster-based permutation test. We then compared modulation between ipsilateral vs. contralateral contacts using the group-level Yate's z-test. 91% of participants and 46.8% of hippocampal gray matter contacts (n = 149) exhibited significant beta-band ERD during the Delay phase compared to baseline. During the Response phase, 100% of participants and 69.8% of hippocampal gray matter contacts exhibited significant beta-band decreases. We observed no significant difference between ipsilateral and contralateral contacts (p > 0.05). This study is the first to demonstrate hippocampal beta-band modulation during movement preparation, implying that the hippocampus may be involved during the movement processing.