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 f or reprocessing those words. The dissociation between explicit and imp licit memory for words is a fundamental characteristic of normal cogni tion that could reflect two different functional architectures of the human brain: two separate processing systems or two levels of operatio n of a single system with implicit memory less demanding of that syste m. We present a patient who has a lesion in the right occipital lobe a nd who showed intact explicit and impaired implicit memory for words. The deficit was specific to visual priming. The double dissociation be tween explicit and implicit visual memory for words indicates that sep arate processing systems mediate these two forms of memory, and that a memory system in right occipital cortex mediates implicit visual memo ry for words.