Visual word stem completion priming within and across modalities: a PET study.

Using positron emission tomography, we studied changes in the regional cerebral blood flow (rCBF) associated with cross modality (auditory to visual) and within modality visual priming in a word stem completion task. Compared to baseline completion performance and to within modality visual priming, cross modality priming was associated with increased rCBF in prefrontal cortex and decreased rCBF in the left angular gyrus. The results confirm and complement trends observed in a previous study concerning visual to auditory cross modality priming, and suggest that distinct cortical mechanisms may mediate within- and cross modality priming on the stem completion task. The findings are consistent with the neuropsychological data concerning auditory to visual cross modality priming, and indicate involvement of aspects of explicit retrieval and lexical processes in cross modality priming.