Head injury in the champanzee

Abstract

✓ The effect of experimental head injury on the electroencephalogram (EEG) and cortical evoked response was studied in 11 awake, moderately restrained chimpanzees. As a base for comparison with injury effects, the waking and sleeping electroencephalogram (EEG) and the somatic and visual evoked responses (SER and VER) were investigated first. Unusually high voltage occipital waves and a propensity for photic driving characterized the EEG. Controlled blows to the occiput in 10 animals produced reversible depression of consciousness in only four. In those four, the EEG and SER were affected differently immediately after the injury; the SER showing marked suppression while the early EEG was unaffected. Recovery of the SER and of consciousness paralleled each other. With injuries causing prolonged or irreversible loss of consciousness, the later EEG showed depression or large amplitude slow waves, which became isoelectric if the blow was fatal.