Priming by natural category membership in the left and right cerebral hemispheres.

The cerebral representation of category information was examined in a single word priming paradigm, during which the N400 component of the event-related potential (ERP) was recorded. The visual half-field paradigm was employed in order to selectively stimulate the two hemispheres. To investigate which aspects of category membership are relevant in producing priming, two types of related stimuli were presented. In one condition pairs of exemplars had a higher amount of feature overlap (e.g., MOSQUITO-FLEA) than in the other (e.g., SOFA-VASE). Significant priming was obtained only for stimuli in the high feature overlap condition and then only when these were presented to the left visual field (LVF)/right hemisphere (RH). This finding was interpreted within our recent model of semantic memory wherein the right hemisphere represents items on the basis of distributed individual features, whereas the left hemisphere (LH) represents semantic information locally, within a spreading activation system, where priming occurs exclusively through associative links. It was concluded that knowledge regarding category membership is maintained in the RH, on the basis of feature coding.