Levels of word processing and incidental memory: dissociable mechanisms inthe temporal lobe

Word recall is facilitated when deep (e.g. semantic) processing is applied during encoding. This fact raises the question of the existence of specific brain mechanisms supporting different levels of information processing tha t can modulate incidental memory performance. In this study we obtained spa tiotemporal brain activation profiles, using magnetic source imaging, from 10 adult volunteers as they performed a shallow (phonological) processing t ask and a deep (semantic) processing task. When phonological analysis of th e word stimuli into their constituent phonemes was required, activation was largely restricted to the posterior portion of the left superior temporal gyrus (area 22). Conversely, when access to lexical/semantic representation s was required, activation was found predominantly in the left middle tempo ral gyrus and medial temporal cortex. The differential engagement of each m echanism during word encoding was associated with dramatic changes in subse quent incidental memory performance. (C) 2001 Lippincott Williams & Wilkins .