An important component of future-oriented thought involves envisioning oneself participating in a specific future event , a process that might spur the initiation of executive processes to structure behavior. Szpunar et al. report the use of functional neuroimaging to probe brain activity underlying this important mental capacity. To isolate regions particularly important for envisioning the future, they chose a comparison task that did not involve envisioning oneself at a time other than the present. In this task, subjects imagined a familiar individual (Bill Clinton) participating in life-like events with no explicit temporal reference. This condition had neither the aspect of self nor the element of mental time travel.
The authors identified a distributed set of cortical regions that appear to be important for episodic future thought and that are not isolated to regions within frontal cortex. These regions neatly break apart into two sets of regions, each characterized by their pattern of activity across tasks. One set of regions (within left lateral premotor cortex, left precuneus, and right posterior cerebellum) was more active while envisioning the future than while recollecting the past (and more active in both of these conditions than in the task involving imagining another person). These regions have previously been implicated in imagined (simulated) bodily movements. A second set of regions (bilateral posterior cingulate, bilateral parahippocampal gyrus, and left occipital cortex) demonstrated indistinguishable activity during the future and past tasks (but greater activity in both tasks than the imagery control task); similar regions have been shown to be important for remembering previously encountered visual-spatial contexts. Hence, differences between the future and past tasks are attributed to differences in the demands placed on regions that underlie motor imagery of bodily movements, and similarities in activity for these two tasks are attributed to the reactivation of previously experienced visual–spatial contexts. That is, subjects appear to place their future scenarios in well known visual–spatial contexts.
The authors suggest that simulation of bodily actions and reinstatement of visual–spatial context may be particularly relevant to the understanding of the ability to mentally represent a future event.