DOUBLE DISSOCIATION BETWEEN MEMORY-SYSTEMS UNDERLYING EXPLICIT AND IMPLICIT MEMORY IN THE HUMAN BRAIN

Amnesic patients have impaired explicit memory that is evident in poor recall and recognition of words, yet can have intact implicit memory for words as measured by repetition priming, the enhanced efficiency for reprocessing those words. The dissociation between explicit and implicit memory for words is a fundamental characteristic of normal cognition that could reflect two different functional architectures of the human brain: two separate processing systems or two levels of operation of a single system with implicit memory less demanding of that system. We present a patient who has a lesion in the right occipital lobe and who showed intact explicit and impaired implicit memory for words. The deficit was specific to visual priming. The double dissociation between explicit and implicit visual memory for words indicates that separate processing systems mediate these two forms of memory, and that a memory system in right occipital cortex mediates implicit visual memory for words.