Imagining the future: evidence for a hippocampal contribution to constructive processing

Abstract

Imagining future events and remembering past events rely on a common core network, but several regions within this network--including the hippocampus--show increased activity for imagining future events compared to remembering past events. It remains unclear whether this hippocampal activity reflects processes related to the demands of constructing details retrieved across disparate episodic memories into coherent imaginary events, encoding these events into memory, novelty detection, or some combination of these processes. We manipulated the degree of constructive processing by comparing activity associated with the initial construction of an imagined scenario with the re-construction of an imagined scenario (imagine vs. re-imagine). After accounting for effects of novelty and subsequent memory, we found that a region in the hippocampus was preferentially activated for newly constructed imagined events compared with re-imagined events. Our results suggest that the hippocampus may support several distinct but related processes that are critical for imagining future events, and they also indicate that a particular region within posterior hippocampus may uniquely contribute to the construction of imagined future events.

Keywords: autobiographical; episodic memory; fMRI; imagination; simulation.

Figure 1. Experimental design

Figure 2. fMRI images for hippocampal mask

As the hippocampus was an a priori region of interest, activations are presented at a p < .05 threshold corrected for multiple comparisons with a p = .005 voxel-level threshold and extent threshold of 17 voxels with the whole brain masked to only show voxels within the bilateral hippocampus. L, left; R, right.

Figure 3. fMRI images for whole-brain

Whole-brain activations are significant at a p < .05 threshold corrected for multiple comparisons with a p = .001 voxel-level threshold and minimum extent threshold of 89 voxels. L, left; R, right.