Altitude and time of day effects on EEG spectral parameters.

Electroencephalographic (EEG) recordings were obtained from nine male subjects at sea level and again following rapid ascent to high altitude (4300 meters) at 0900, 1600, and 1830 h. Electroencephalographic data were subjected to Fast Fourier Transformation and analyzed for beta, spindle, alpha, theta, delta, and total amplitudes. Total amplitude increased from baseline to altitude while relative theta (absolute theta/total amplitude) decreased from baseline to altitude. Amplitude for absolute and relative spindle and total amplitude increased across the day. The results indicate that altitude exerts an effect on the waking electroencephalogram which can be quantified via spectral analysis.