Visual implicit memory in the left hemisphere: Evidence from patients withcallosotomies and right occipital lobe lesions

Identification of visually presented objects and words is facilitated by im plicit memory for past visual experiences with those items. Several behavio ral and neuroimaging studies suggest that this form of memory is dependent on perceptual processes localized in the right occipital lobe. We tested th is claim by examining implicit memory in patients with extensive right occi pital lobe lesions, using lexical-decision, mirror-reading, picture-fragmen t, and word-fragment-completion tests, and found that these patients exhibi ted normal levels of priming. We also examined implicit memory in patients with complete callosotomies, using standard and divided-visual-field word-f ragment-completion procedures, and found that the isolated left hemisphere exhibited normal priming effects. The results indicate that the right occip ital lobe does not play a necessary role in visual implicit memory, and tha t the isolated left hemisphere can support normal levels of visual priming in a variety of tasks.