Journal of Applied Physiology, Vol 39, Issue 1 109-113, Copyright © 1975 by American Physiological Society
Effect of sojourn at 4,300 m altitude on electroencephalogram and visual evoked response
H. V. Forster, R. J. Soto, J. A. Dempsey and M. J. Hosko
The purpose of the present study was to determine the effect of sojourn at
high altitude on cerebral electrical activity. Electroencephalographic
(EEG) and visual evoked responses (VER) were recorded from seven healthy
males under the following conditions: 1) during the first 2-3 h at 4,300 m
altitude when Pao2 was maintained at 90 mmHg (control condition), 2) during
the first 2-3 h of hypoxia (Pao2 = 40 mmHg), and 3) at 24- to 48-h
intervals during the first 9-12 days of hypoxia. Electrode placement was
according to the 10-20 International Electrode System. The VER was recorded
from an electrode at the inion referred to the left ear. We found no
significant changes from control cerebral electrical activity during the
first 2-3 h of hypoxia. One subject's VER amplitude was greater than
control on the 2nd and 3rd days of hypoxia and a similar change from
control was consistently evident in a second subject beginning the 5th day
of hypoxia. These changes suggest cortical depression. After the 5th day
changes occurred in the remaining subjects which would be consistent with
cortical excitation. In three subjects, EEG frequency was increased,
amplitude decreased, and/or spiking became evident. In four subjects VER
amplitude was reduced. Our findings provide support for the hypothesis that
certain behavioral and physiological changes induced by sojourn at altitude
could be caused by alterations in central nervous system function.
