HEMISPHERIC-SPECIALIZATION IN HUMAN DORSAL FRONTAL-CORTEX AND MEDIAL TEMPORAL-LOBE FOR VERBAL AND NONVERBAL MEMORY ENCODING

The involvement of dorsal frontal and medial temporal regions during t he encoding of words, namable line-drawn objects, and unfamiliar faces was examined using functional magnetic resonance imaging (fMRI). Robu st dorsal frontal activations were observed in each instance, but late ralization was strongly dependent on the materials being encoded. Enco ding of words produced left-lateralized dorsal frontal activation, whe reas encoding of unfamiliar faces produced homologous right-lateralize d activation. Encoding of namable objects, which are amenable to both verbal and nonverbal encoding, yielded bilateral dorsal frontal activa tion. A similar pattern of results was observed in the medial temporal lobe. These results indicate that regions in both hemispheres underli e human longterm memory encoding, and these regions can be engaged dif ferentially according to the nature of the material being encoded.