Neuroimaging of priming: New perspectives on implicit and explicit memory

Priming refers to a change in the ability to identify or produce an item as a consequence of a specific prior encounter. Priming has been studied extensively in cognitive studies of healthy volunteers, neuropsychological investigations of brain-damaged patients, and, more recently, studies using modern functional neuroimaging techniques such as positron emission tomography and functional magnetic resonance imaging. We review recent neuroimaging studies that have converged upon the conclusion that priming is reliably accompanied by decreased activity in a variety of brain regions. The establishment of this cortical signature of priming is beginning to generate new hypotheses concerning the relation between priming and explicit retrieval, which we illustrate by considering recent experiments on within-and cross-modality priming.