Thursday, May 10, 2007

Imagining the Past, Remembering the Future

Symposium Session 4 at the CNS 2007 Annual Meeting was on Projecting the Past Into the Future: The Cognitive Neuroscience of Prospective Thought.
Summary: Humans spend a significant amount of time envisioning possible future events, yet the bulk of cognitive neuroscience research has focused on how humans re-experience past happenings. Such an oversight is surprising as future-oriented thought makes it possible for humans to anticipate events, formulate strategies based on previous experiences, and override momentary needs in pursuit of longer-term goals. In this symposium we present findings that suggest the brain evolved sophisticated mechanisms for envisioning the future. Schacter's work suggests that to deal effectively with the future people utilize the psychological and neural processes involved in remembering the past. Based on her recent findings, McDermott suggests that the ability to envision future events involves the simulation of behavior and the reinstatement of visuo-spatial contexts. Buckner will present data suggesting that one fundamental function of the brain is simulating alternative strategies and perspectives. Finally, Bar presents a framework linking perception, memory and predictions and argues that the mind is constantly anticipating "what's next" based on analogies with past experiences. As a package, these findings suggest that one core component of human cognition is anticipating possible future scenarios based on memories of past events.
The Neurocritic wrote about this topic (and the papers by Addis et al., 2007 [Schacter Lab], Szpunar et al., 2007 [McDermott Lab], and Hassabis et al., 2007 [Maguire Lab]) back in February. Was anything new presented? Not too much. The audience laughed [audibly] when Kathleen McDermott described the experimental control condition for imagining one's own future (imagine former President Clinton doing...) and how participants could easily imagine him in various scenarios. I snorted [inaudibly] when she admitted that interpretation of her results [i.e., activation of posterior cingulate cortex, parahippocampal gyrus, and occipital regions reflect autobiographical memory and spatial navigation] relies on reverse inference1. McDermott did describe a new study with an alternate control condition asking the participants to imagine themselves in an unfamiliar future situation (e.g., scuba diving, bullfight, jungle), so that self-referential (not Clinton-referential) processing was involved in all three conditions. The original result was replicated (Future familiar = Past familiar > Future novel).

Schacter mentioned a paper under review that looked at the effects of aging on the level of detail produced when imagining future events. This experiment followed from the findings of Levine et al. (2002), which demonstrated that older adults show a reduced level of contextual (episodic) detail when recalling autobiographical events; instead, they rely more on "semantic details not connected to a particular time and place" than do young adults. The new Schacter et al. results found the same thing in elderly participants imagining the future.

For his conclusion, Schacter acknowledged that no regions of the brain were more active for remembering the past vs. imagining the future in his study (Addis et al., 2007). It's a confounded comparison: we should imagine an alternate past instead of recalling an existing one.

What about Buckner and Bar? Certain aspects of their talks merit future posts of their own...

1 inferring the participants' emotional state from the observed pattern of brain activity.


Addis DR, Wong AT, Schacter DL. (2007). Remembering the past and imagining the future: Common and distinct neural substrates during event construction and elaboration. Neuropsychologia 45: 1378-1385.

Hassabis D, Kumaran D, Vann SD, Maguire EA. (2007). Patients with hippocampal amnesia cannot imagine new experiences. Proc Natl Acad Sci 104: 1726-31.

Levine B, Svoboda E, Hay JF, Winocur G, Moscovitch M. (2002). Aging and autobiographical memory: dissociating episodic from semantic retrieval. Psychol Aging 17:677-89.

Szpunar KK, Watson JM, McDermott KB. (2007). Neural substrates of envisioning the future. Proc. Natl. Acad. Sci. 104:642-7.

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