Hippocampal contributions to the episodic simulation of specific and general future events

Abstract

Recent studies have demonstrated that remembering past experiences and imagining future scenarios recruits a core network including the hippocampus. Even so, constructing future events engages the hippocampus more than remembering past events. This fMRI study examined whether increased hippocampal activity for future events includes both specific and general events. Participants constructed specific and general past and future events during fMRI scanning. We replicated previous findings of increased activity in the right anterior hippocampus when constructing future relative to past events, and when constructing specific relative to general events. Importantly, both effects were driven by a significant interaction between temporal direction and specificity, with specific future events resulting in more activity than other conditions, including general future events. No regions exhibited greater activity during the construction of past relative to future events, or general relative to specific events. These results suggest that the process of constructing a detailed representation of a novel and specific future event differentially engages the right anterior hippocampus compared with other forms of event simulation and recall. Future work is needed to disambiguate the role of encoding, novelty and detail recombination in engaging the right anterior hippocampus during simulation.

Figure 1

Right hippocampal activation identified by the future > past (left) and specific > general (right) contrasts are shown at P-_uncorrected<.005 (note that both activations survive small volume correction, P-_FDR≤.05). Percent signal change extracted from the peak voxel is shown for all conditions (GF=general future; SF=specific future; GP=general past; SP=specific past). All co-ordinates are in Talairach space.