EFFECTS OF SURGERY IN UNILATERAL MEDIAL TEMPORAL-LOBE REGIONS ON VERBAL EXPLICIT AND IMPLICIT MEMORY

Verbal memory was tested through free-recall and priming in unilateral anterior temporal lobectomy (TL) and in selective amygdalohippocampec tomy (SAH) patients in order to determine if more memory is available, implicitly, than is indicated by free-recall in left- versus right-si ded cases. Neither recall nor priming distinguished between TL and SAH patients. Consistent with other findings, free-recall was asymmetrica l, worse in left-sided than in fight-sided patients (regardless of sur gery). On the other hand, priming revealed a left-fight symmetrical im plicit memory component as well as a memory component (interpreted as recognition) which was lower in left- than in right-sided patients. Th e anterior temporal lobe on either side does not seem to be involved i n implicit memory. The results indicate that more verbal memory is ava ilable, implicitly, in long-term memory in TL and SAH than free-recall alone indicates, and unlike free-recall, it is left-right symmetrical .