People can consciously re-experience past events and pre-experience possible future
events. This fMRI study examined the neural regions mediating the construction and
elaboration of past and future events. Participants were cued with a noun for 20s
and instructed to construct a past or future event within a specified time period
(week, year, 5-20 years). Once participants had the event in mind, they made a button
press and for the remainder of the 20s elaborated on the event. Importantly, all events
generated were episodic and did not differ on a number of phenomenological qualities
(detail, emotionality, personal significance, field/observer perspective). Conjunction
analyses indicated the left hippocampus was commonly engaged by past and future event
construction, along with posterior visuospatial regions, but considerable neural differentiation
was also observed during the construction phase. Future events recruited regions involved
in prospective thinking and generation processes, specifically right frontopolar cortex
and left ventrolateral prefrontal cortex, respectively. Furthermore, future event
construction uniquely engaged the right hippocampus, possibly as a response to the
novelty of these events. In contrast to the construction phase, elaboration was characterized
by remarkable overlap in regions comprising the autobiographical memory retrieval
network, attributable to the common processes engaged during elaboration, including
self-referential processing, contextual and episodic imagery. This striking neural
overlap is consistent with findings that amnesic patients exhibit deficits in both
past and future thinking, and confirms that the episodic system contributes importantly
to imagining the future.