Performance recovery following +Gz-induced loss of consciousness.

Seven male baboons (average weight, 20.6 kg) were trained in a simple shock-avoidance performance task on the USAFSAM centrifuge. A red light was presented to the baboon at approximate 2-s intervals. The animal was allowed 1 s to turn off the light or receive a 1-s shock. The shock could be abbreviated by a late trigger pull. Thus, the animal could avoid, escape, or accept the full shock. EEG was monitored from three transcranial stainless steel electrodes. Loss of consciousness (LOC) was induced by a rapid onset (4 or 6/s) exposure to 8 +Gz and sustained until LOC was identified by a near isoelectric EEG signal. Performance recovery time was measured from the return of EEG activity to the time when the animal resumed the performance task. These data were compared with previously obtained human data and found to be very similar. Also, it was found that time of performance recovery became significantly shorter after multiple LOC exposures and the performance recovery time significantly increased with increased time of unconsciousness. This study demonstrates the utility of the baboon as an animal model for G-induced LOC (G-LOC) research.