Reinstatement of encoding context during recollection: behavioural and neuroimaging evidence of a double dissociation.

In both a behavioural and neuroimaging study, we examined whether memory performance and the pattern of brain activation during a word recognition task differed depending on the type of visual context presented during encoding. Participants were presented with a list of words, paired with either a picture of famous face, a famous scene, or a scrambled image, to study for a later recognition test. During the recognition test, participants made 'remember', 'know', or 'new' responses to words presented alone. In the neuroimaging experiment, the retrieval phase was scanned using event-related fMRI and brain activation was compared for remember and know responses given to words studied with famous faces and famous scenes. Behaviourally, in both studies, memory was enhanced if initial encoding was accompanied by a meaningful image (famous face or famous scene) relative to a scrambled image which contained no semantic information. At the neural level, whole brain analysis showed a double dissociation during recollection: BOLD signal in the right fusiform gyrus (within the Fusiform Face Area) was higher for remember responses given to words studied with famous faces compared to famous scenes, and was higher in the left parahippocampus (within the Parahippocampal Place Area) for words studied with famous scenes relative to famous faces. No such differential activation was found for know responses. Results suggest that participants spontaneously integrate item and meaningful contexts at encoding, improving subsequent item recollection, and that context-specific brain regions implicated during encoding are recruited during retrieval for the recollective, but not familiarity, memory process.