Differential fMRI subsequent memory for context unattended to at both study and test, vs. attended items

Subsequent memory refers to assessment of differential neural encoding-related activation (DM) for subsequently remembered versus forgotten material. In the present study we assessed DM for context which was unattended-to at both study and test, and for its attended target. At study, composite stimuli containing (attended) black words superimposed on grey (unattended) words were presented. Participants performed an incidental encoding task of vowel counting on the black target words. A subsequent recognition test included four types of stimuli, obtained by crossing the targetcontext dimension with old-new status (old targets presented on old contexts; old targets presented on new contexts, new targets presented on old contexts, and new targets presented on new contexts). Stimuli with at least one old component were relevant to the DM analysis. Interaction contrasts revealed differential DM activation profiles in prefrontal cortex, associated with attended target memory and memory for the unattended context. Successful encoding-related activation for attended targets without their contexts (compared to targets presented with their original contexts) was observed in bilateral BA 10; A distinctively different activation pattern was observed for successful encoding of unattended contextual information. Results reveal that contextual information unattended-to at both study and test is not only encoded, but its encoding also qualitatively differs from that of attended targets; i.e., it is not merely a paler version of the pattern associated with attended target encoding