The Contextual Association Network Activates More for Remembered than for Imagined Events.

The human capacities to remember events from the past and imagine events in the future rely on highly overlapping neural substrates. Neuroimaging studies have revealed brain regions that are more active for imagined events than remembered events, but the reverse pattern has not been shown consistently. Given that remembered events tend to be associated with more contextual information ( Johnson et al. 1988), one might expect a set of regions to demonstrate greater activity for remembered events. Specifically, regions sensitive to the strength of contextual associations might be hypothesized to show greater activity for remembered events. The present experiment tests this hypothesis. fMRI was used to identify brain regions within the contextual association network ( Bar and Aminoff 2003); regions within this network were then examined to see whether they showed differential activity during remembering and imagining. Bilateral regions within the parahippocampal cortex and retrosplenial complex responded more strongly to remembered past events, supporting work that suggests these events have more contextual information associated with them. Follow-up voxel-wise analysis demonstrated the specificity of these results, as did re-analysis of previous experimental datasets. These results suggest that a key differentiating feature of remembering and imagining is the strength of contextual associations.