Effects of Human Hippocampal Ablation

Abstract

IlE hypothalamus, anterior thalamic nuclei, gyrus cinguli, hippoeampus, and their connections were believed by Papez 5 to constitute a harmonious mechanism which may elaborate the functions of emotion as well as participate in emotional expression. A broader concept of the function of the limbic system was expressed by Herrick, 3 who considered the limbic system an of all neocortical functions facilitating or inhibiting not only affective behavior, but memory and learning as well. The hippocampus itself is regarded by many authors as the hub of the limbic system. Papez speaks of the central emotive process of cortical origin being built up in the hippocampal formation before being relayed to the mammillary bodies and the anterior nuclei of the thalamus. Grunthal 2 suggests that the hippocampus acts as a catalytic activator essential for the affective and neocortical activity. To gain a greater insight into the function of the hippocampus, a technique for subtotal hippocampectomy was developed in the cat and monkey. 1,9 Following hippocampectomy, a marked taming effect was observed, similar to that described by Kliiver and Bucy 4 and Sehreiner and KlingJ During these studies it was noted that following hippocampectomy the animals showed less response to painful stimuli. Whether this was due to diminished perception or reactivity remained undetermined. The laboratory findings provided an encouraging basis for further exploration of the effects of hippocalnpectomy on a clinical level. It appeared that the procedure might prove useful in psychosurgery and pain control. The transfer of a laboratory procedure to the clinical level is fraught with many unexpected pitfalls, and it was decided, therefore, to use the procedure only for intractable pain due to widespread careinomatosis, or