The impaired learning of semantic knowledge following bilateral medial temporal-lobe resection.

The integrity of several aspects of semantic memory (including knowledge of the meaning, lexical status, perception, and pronunciation of words and famous names) was examined in H.M., a patient with anterograde amnesia following bilateral medial temporal-lobe excision. Despite normal memory for such semantic knowledge acquired prior to the onset of his amnesia in 1953, H.M. showed a severe deficit in memory for semantic information encountered subsequently. In combination with the previously reported impairments in new learning shown by H.M., the deficits observed here point to an association between semantic and episodic memory, and do not lend support to a distinction between them. The acquisition of semantic and episodic information, therefore, appears to depend upon a common memory system that requires the intact functioning of medial temporal-lobe structures.