Page 40 - WNS 2022 E-Program Booklet

Baseline Hippocampal Beta Band Power Is Lower in the Presence of
Movement Uncertainty
Brian Lee, MD Ph.D Department of Neurological Surgery Keck School of Medi-
cine of USC
Co-authors: Zachary D. Gilbert, BS, Roberto Martin del Campo-Vera, PhD
Austin M. Tang, MPH, Kuang-Hsuan Chen, PhD, Rinu Sebastian, MS
Arthur Shao, BS, Emiliano T, Abarsi, BA, Ryan S. Chung, BA, Andrea Leonor,
MS, Shivani Sundaram, BA, Christi Heck, MD, George Nune, MD
Charles Y. Liu, MD, PhD, Spencer Kellis, PhD
Introduction This study aimed to characterize hippocampal neural signatures of
uncertainty by measuring beta band power in the period prior to movement
cue.
Methods
Participants with epilepsy were implanted with hippocampal depth electrodes
for stereo electroencephalographic (SEEG) monitoring. Hippocampal beta (13-
30 Hz) power changes have been observed during motor tasks such as the
direct reach (DR) and Go/No-Go (GNG) tasks. The primary difference between
the tasks is the presence of uncertainty about whether movement should be
executed. Previous research on cortical responses to uncertainty has found
that baseline beta power changes with uncertainty. SEEG data were sampled
throughout phases of the DR and GNG tasks. Beta-band power during the
fixation phase was compared between the DR and GNG task using a Wilcoxon
rank sum test. This unpaired test was also used to analyze response times
from cue to task completion between tasks.
Results
Eight patients who performed both reaching tasks were analyzed in this study.
Movement response times in the GNG task were on average 210 milliseconds
slower than in the DR task. All patients exhibited a significantly increased re-
sponse latency in the GNG task compared to the DR task (Wilcoxon rank-sum
p-value < 0.001). Six out of eight patients demonstrated statistically significant
differences in beta power in single hippocampal contacts between the fixation
phases of the GNG and DR tasks. At the group level, baseline beta power was
significantly lower in the GNG task than in the DR task (Wilcoxon rank-sum p-
value < 0.001).
Conclusions
This novel study found that, in the presence of task uncertainty, baseline beta
power in the hippocampus is lower than in its absence. This finding implicates
movement uncertainty as an important factor in baseline hippocampal beta
power during movement preparation.

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