Effects of simulated high altitude on event-related potential (P300) and auditory brain-stem responses.
OBJECTIVE
This study investigated the effect of hyobaric hypoxia on cognitive function.


METHODS
We recorded the auditory brain-stem response (ABR) and auditory-evoked event-related potentials (ERP) in 7 male subjects during a rapid ascent to a simulated 4500 m altitude from their acclimatized altitude of 610 m. The amplitude and latency of each component of ABR and of ERP were assessed.


RESULTS
Compared with the values at 610 m, at 4500 m the latencies of both waves I and V of ABR significantly increased, with no change in I-V interpeak latency; and the amplitude of wave I decreased, with no change in the amplitude of wave V. The increase in altitude affected neither the amplitude nor the latency of N100. The P300 latency was prolonged significantly after exposure to hypobaric-hypoxic conditions for 2h, with no significant change in amplitude. At 4500 m, the P300 latency returned to the baseline value after oxygen was inhaled.


CONCLUSIONS
Our results suggest it is possible to boost cognitive processing by supplying oxygen even when auditory stimulus intensity decreases under hypobaric and hypoxic conditions, and that P300 latency is affected by hypoxic more than hypobaric conditions.


CONCLUSIONS
This study demonstrated that each component of ABR and the latency of both N100 and P300 are important to record when the effects of hypobaric hypoxia on cognitive function are investigated.
Hayashi
Ryoichi
R
Third Departments of Internal Medicine, Shinshu University School of Medicine, Matsumoto 390, Japan. mail1@okaya-hosp.jp
Matsuzawa
Yukinori
Y
Kubo
Keishi
K
Kobayashi
Toshio
T
D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D000531:Altitude; D000704:Analysis of Variance; D004307:Dose-Response Relationship, Radiation; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D006801:Humans; D008297:Male; D011930:Reaction Time / Q000502:physiology