Toward the neural basis of verbal priming: a cognitive-neuropsychological synthesis.

Repetition priming is a mnemonic phenomenon that has attracted considerable attention from neuropsychologists and cognitive scientists. In an attempt at elucidating the putative mechanisms of priming, the present review draws on evidence from both domains. The review is restricted to verbal priming of visually presented stimuli--an area that accounts for the majority of empirical studies of priming. A number of theoretical accounts are presented. The interim conclusion is that neither multiple systems nor unitary system-multiple process theories can adequately explain the data on priming, although both contain many valid components. An integrative model is proposed to improve the explanation of the empirical evidence. The central assertion of the proposed model is that repetition priming depends on perceptual processes that can be mapped on specific neural systems. It is postulated that individual differences in perceptual processing ability predict variability in memory performance. It is proposed that data-driven priming of verbal stimuli critically depends on the activity of primary and secondary visual cortices in the right hemisphere, whereas conceptually-driven priming is hypothesized to rely on the activities of higher order tertiary association cortices in language areas and more anterior neocortical areas.