Changes in Electroencephalogram Spectra during Repeated Exposure to +Gz Acceleration.

Eight human subjects experienced a series of +Gz acceleration profiles reaching peak values of +41/2 Gz and +6 Gz. Each subject experienced six 45-second +Gz exposures within 15 minutes. Electroencephalograms (EEG) were made throughout this period and subjected to a narrow-band spectral analysis within 10-second epochs. The subjects wore protective G-suits, and did not experience impairment of central vision during the runs analyzed. Small increases in spectral intensity of the EEG were seen during eyes-closed, resting epochs following +Gz exposure. These increases did not change overall shape of spectral profiles and did not exceed normal levels of EEG intensity. During +Gz forces with eyes open, the raw EEG was dominated by electromyographic (EMG) activity, which was typically proportional to instantaneous +Gz force but might also reflect paroxysmal whole-body contractions occurring at scattered points in the +Gz exposure profile. Increased EEG intensities greatly exceeding basal levels for certain narrow frequency bands were observed during actual +Gz exposures. In all subjects, a return to normal EEG spectral intensity profiles took place within 30 seconds of termination of acceleration. (Modified author abstract)
Prepared in cooperation with School of Aerospace Medicine, Brooks AFB, Tex.