Form-specific explicit and implicit memory in the right cerebral hemisphere.

Abstract

Results from 2 divided visual field (DVF) experiments indicate that in some conditions both explicit and implicit memory are greater when same-letter-case stimuli are presented directly to the right cerebral hemisphere (in the left visual field) than when they are presented directly to the left (in the right visual field). Explicit memory was measured with word-stem cued recall, and implicit memory was measured with word-stem completion priming. Words were presented centrally during encoding, and word stems were presented directly to the right hemisphere or to the left hemisphere during testing. Results for explicit memory contrast with findings from a previous DVF study that used a different procedure, those for implicit memory replicate previous DVF findings, and both results corroborate positron emission tomography findings. We suggest that a formspecific system in the right hemisphere may contribute to both explicit and implicit memory. Research that uses positron emission tomography (PET) is currently helping to delineate areas of the human brain that play specific roles in reading and remembering words (for a review, see Petersen & Fiez, 1993). One recent discovery from PET is that a region of posterior cortex in the right cerebral hemisphere implements at least some of the processing that underlies visual repetition priming of words (Squire et al., 1992). This discovery complements recent findings from divided visual field (DVF) experiments. Under certain conditions, visual repetition priming of words is greater when test stimuli are presented directly to the right hemisphere (in the left visual field) than directly to the left hemisphere (in the right visual field; Marsolek, Kosslyn, & Squire, 1992). A second important finding from PET is that processing in the hippocampal region of the right hemisphere is involved in visual cued recall of words (Squire et al., 1992). However, findings from the DVF experiments do not corroborate this PET result. At least