MEMORY IN MONKEYS SEVERELY IMPAIRED BY COMBINED BUT NOT BY SEPARATE REMOVAL OF AMYGDALA AND HIPPOCAMPUS

THE profound anterograde amnesia that has been attributed in the clinical literature to damage of the hippocampal system1,2 has not been observed in animals with such damage. Hippocampal-system lesions in animals do markedly impair some forms of spatial memory3,4, but the effects on other forms of memory have generally seemed minor5,6 compared with the dramatic disorder described in man7,8. This discrepancy between the clinical and animal literature could indicate a true evolutionary shift in the functions of the hippocampus9,10, or, at the other extreme, it could simply reflect the use of incommensurate measures across species 11,12. (Strong support for this second interpretation has been provided by Gaffan13.) A third possibility, however, is that the discrepancy points to inaccurate localisation of the neuropathology in man that is responsible for the profound amnesia. Support for this last alternative comes from new evidence in monkeys indicating that a striking impairment in visual memory can be produced by the combined ablation of the hippocampal formation and the amygdaloid body, but not by ablation of either of these structures alone. © 1978 Nature Publishing Group.