— Annapurna Base Camp —
Studying the Brain at High Altitude
This two week expedition aimed to establish a method of measuring and characterizing task-related neuronal activity that might be relevant to altitude-induced neurological dysfunction and ground-based neurological disease. Our trek ascended to 4,130 meters to Annapurna Base Camp, home to the tenth highest and most deadly mountain in the world. This project was generously funded by the Harvard Travellers Club with equipment sponsorships from Brain Vision LLC & J+S Vision.
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Read our Letter to the Editor in the Journal of High Altitude Medicine & Biology
ENHANCED NEURONAL SYNCHRONY DURING SKILLED REACHING AT HIGH ALTITUDE
Matt Gaidica1 and Jenna Clem2
1Neuroscience Graduate Program
2Department of Molecular, Cellular and Developmental Biology
University of Michigan, Ann Arbor, USA
Objective: To establish a method of measuring and characterizing task-related neuronal activity during a high altitude ascent.
Methods: We implemented cortical electroencephalography (EEG) on two healthy, right-handed subjects during a self-paced skilled reaching task over a seven-day ascent to Annapurna Base Camp in the north-central region of Nepal.
Results: We correlated task-centered sensorimotor oscillatory activity of five physiologically relevant EEG bands (Delta: 0.5-3.5 Hz; Theta: 4-8 Hz; Alpha: 7.5-12.5 Hz; Beta: 13-30 Hz; Gamma: 30-100 Hz) with daily measures of altitude, ascent, and blood oxygen saturation (SpO2). Our data reveal a significant positive correlation between sensorimotor delta phase-amplitude synchrony and altitude.
Conclusions: Our method represents a novel approach to studying the brain at high altitude and revealed task-related neuronal adaptations. Although we experienced significant changes in SpO2 at altitude, our task performance remained unchanged. This suggests that the enhanced delta phase and amplitude characteristics of our EEG activity at high altitude likely represent the recruitment of additional sensorimotor resources to maintain task coordination. We hypothesize that the homeostatic delta oscillations represent a separate oscillatory system that is driving task-related, cortical-level compensation. While healthy individuals may have relatively robust compensation machinery, it may breakdown in subjects with disease, under abnormal stress, or generally in situations where basic brain functions serving survival are paramount. Therefore, potential countermeasures for high altitude mountaineers may benefit from a dual approach: one for supplementing homeostatic processes and another that enhances cortical-specific pacemaker networks.
Acknowledgements: The Harvard Travellers Club financially supported this study. Brain Products, LLC, sponsored all equipment. This study received “non-regulated” status by the University of Michigan Medical School Institutional Review Board (ID: HUM00119637).