G-FORCE INDUCED ALTERATIONS IN RAT EEG ACTIVITY - A QUANTITATIVE-ANALYSIS

A major physical limitation affecting pilots is G-force (+G(z), head-t o-foot inertial load) induced loss of consciousness. Previous studies have shown that +G(z) produces qualitatively similar effects on human and rat EEG activity. The present study sought to quantitatively corre late changes in rat EEG activity with increasing +G(z) levels. A front al-parietal differential electrode recorded rat EEG data during +G(z) exposures (30 s) ranging from +0.5 to +25.0 G(z). Acceleration levels less than or equal to+10 G(z) had little effect on EEG activity. Accel eration levels of +15 to +20 G(z) were associated with increased EEG s lowing, depression and sharp waves. Acceleration levels greater than o r equal to+17.5 G(z) evoked burst suppression followed by isoelectric activity. Times to first onset of delta, depressed, and isoelectric EE G activity were approximately 12, 14 and 18 s, respectively. Accelerat ion effects on delta (1-4 Hz), theta (5-8 Hz), alpha (9-12 Hz), beta ( 13-30 Hz) and total (1-30 Hz) EEG powers were examined using Fourier t ransform analysis. EEG measures with the most predictive value at the following post-acceleration onset times (PAOT) were as follows (in s); increasing theta power: PAOT 0-2, decreasing delta power: PAOT 3-9, a nd decreasing beta power: PAOT greater than or equal to 12. This study provides a quantitative description of +G(z)-induced alterations in E EG magnitude, time course and spectral content. Additionally, several EEG measures were identified which correlated with acceleration level at specific post-acceleration onset times. (C) 1997 Elsevier Science I reland Ltd.