Episodic Simulation of Future Events and the Medial

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Episodic Simulation of Future Events and the Medial Temporal Lobe Daniel L. Schacter Harvard

Episodic Simulation of Future Events and the Medial Temporal Lobe Daniel L. Schacter Harvard University Banbury Center, April 13, 2009

Amnesic Patient KC: No Past, No Future Tulving, Canadian Psychology (1985)

Amnesic Patient KC: No Past, No Future Tulving, Canadian Psychology (1985)

Commonalities between Past and Future Events * Amnesic patients: Difficulties imagining personal futures/novel scenes

Commonalities between Past and Future Events * Amnesic patients: Difficulties imagining personal futures/novel scenes (Tulving, 1985; Klein, Loftus, & Kihlstrom, 2002; Hassabis et al. , 2007) * Depressed patients/older adlts: Reduction in episodic specificity of past events and future events significantly correlated (Williams et al. , 1996; Addis, Wong, & Schacter, 2008) * Cognitive studies: Manipulations/individual differences similarly influence past and future events (D’Argembeau & van der Linden, 2004; 2006; Spreng & Levine, 2006) • Neuroimaging: Similar areas active when remembering past and imagining future (Addis, Wong, & Schacter, 2007; Hassabis et al. , 2007; Okuda et al. , 2003; Szpunar, Watson, & Mc. Dermott, 2007) Reviewed by Schacter, Addis, & Buckner, Nature Reviews Neuroscience (2007); Year in Cognitive Neuroscience, Annals of the NY Academy of Sciences (2008)

� Core Network of Regions Involved in Remembering the Past, Imagining the Future, &

� Core Network of Regions Involved in Remembering the Past, Imagining the Future, & Related Forms of Mental Simulation Schacter, Addis, & Buckner, Nature Reviews Neuroscience (2007)

Constructive Episodic Simulation Hypothesis (Schacter & Addis, 2007, Nature; Phil. Trans. Royal Society B)

Constructive Episodic Simulation Hypothesis (Schacter & Addis, 2007, Nature; Phil. Trans. Royal Society B) – Episodic memory involves constructive processes: *Details are stored as fragments in cortical regions; during retrieval they are reactivated by these cortices and reintegrated by hippocampus into a coherent event. – The constructive nature of episodic memory makes it well-suited to building simulations of possible future events: *Enables one to extract details from past events *Enables the flexible recombination of details from past events into coherent future scenarios – which likely relies heavily on relational processing capacities supported by the hippocampal region. – Though well-suited to simulating future events, constructive nature of episodic memory has a cost: *Miscombination of details can result in memory errors such as false recognition.

Past & Future: A Neuroimaging Approach • We used event-related f. MRI to examine

Past & Future: A Neuroimaging Approach • We used event-related f. MRI to examine the neural substrates of past and future event construction and elaboration; focus on everyday autobiographical events • Instructions (14 young adult participants): –Cued to recall past event or imagine future event –Future events should be novel and plausible –Three time periods for both past and future: last/next week, last/next year, last/next 5 -20 yrs. Subjects describe events in post-scan interview Addis, Wong, & Schacter (Neuropsychologia, 2007)

Past and Future: Common Neural Substrates? CONSTRUCTION CUE 0 2 ELABORATION RT 20 •

Past and Future: Common Neural Substrates? CONSTRUCTION CUE 0 2 ELABORATION RT 20 • Event cue screen presented for 20 s • Button press made when event in mind – signifies end of construction & beginning of elaboration • 24 past and 24 future event task trials FUTURE event PAST event Last 5 -20 yrs CAR OR Next year DRESS RATINGS 35 time • 3 scales, shown consecutively each for 5 s Detail task 12345 time-period Emotion cue 12345 Perspective field/observer

Past and Future: Control Tasks CONSTRUCTION CUE 0 2 ELABORATION RT RATINGS 20 •

Past and Future: Control Tasks CONSTRUCTION CUE 0 2 ELABORATION RT RATINGS 20 • Event cue screen presented for 20 s • Button press made when event in mind – signifies end of construction & beginning of elaboration • 24 semantic and 24 visuospatial task trials 35 time • 3 scales, shown consecutively each for 5 s Detail 12345 WORDS-sentence 2 related words CABLE OBJECTS- triangle OR bigger / smaller LEAF task items to generate cue Relatedness 12345 Difficulty easy / difficult

Past and Future Events: Common Neural Substrates? CUE CONSTRUCTION ELABORATION OVERLAP: FUSIFORM & R.

Past and Future Events: Common Neural Substrates? CUE CONSTRUCTION ELABORATION OVERLAP: FUSIFORM & R. MIDDLE OCCIPITAL Cue processing / object recognition past events future events L. HIPPOCAMPUS Initial retrieval control tasks

Construction: Neural differentiation CUE CONSTRUCTION ELABORATION future > past R. HIPPOCAMPUS R. FRONTAL POLE

Construction: Neural differentiation CUE CONSTRUCTION ELABORATION future > past R. HIPPOCAMPUS R. FRONTAL POLE (BA 10) Novelty encoding? Recombining details to form specific episodes ? past events future events Novelty / Recombining details control tasks

Past and Future Events: Common Neural Substrates? CUE CONSTRUCTION ELABORATION L. FRONTAL POLE OVERLAP:

Past and Future Events: Common Neural Substrates? CUE CONSTRUCTION ELABORATION L. FRONTAL POLE OVERLAP: L. HIPPOCAMPUS Self referential processing L. TEMPORAL POLE Conceptual details past events Reintegrate/recombine event details MEDIAL PARIETAL / PARAHIPPOCAMPUS Imagery / context future events control tasks

Past and Future Detail Background Are hippocampal responses to detail similar for past and

Past and Future Detail Background Are hippocampal responses to detail similar for past and future events? Constructive Episodic Simulation Hypothesis: – Past events: reintegration of relevant event details – Future events: recombination of various details into novel event

Past and Future Detail Method CONSTRUCTION CUE 0 2 RATE DETAIL ELABORATION RT RECALL

Past and Future Detail Method CONSTRUCTION CUE 0 2 RATE DETAIL ELABORATION RT RECALL PAST Last 5 -20 yrs CAR IMAGINE FUTURE Next year DRESS 20 25 time RATE DETAIL 12345 – Past & future detail did not differ on average – Parametric modulation: what regions vary with amount of detail?

Past and Future Detail Addis and Schacter (2008, Hippocampus) Posterior HC activity correlates with

Past and Future Detail Addis and Schacter (2008, Hippocampus) Posterior HC activity correlates with past AND future detail: - Retrieval of details from past events? More anterior HC activity correlates with future detail - Flexible recombination of details from past events? Cf. Preston et al. (2004)

Hippocampal Response to Recombined Details Preston et al. (2004): Recombined details engage anterior hippocampus

Hippocampal Response to Recombined Details Preston et al. (2004): Recombined details engage anterior hippocampus

Constructive Episodic Simulation: Two Conceptual Issues 1. Comparison has focused on remembering the past

Constructive Episodic Simulation: Two Conceptual Issues 1. Comparison has focused on remembering the past vs. imagining the future, but past/future confounded with remembering/imagining: Are observed patterns specific to imagining future events or associated with more general imagination/simulation? According to constructive episodic simulation hypothesis, critical process of recombining event details should occur regardless of whether individuals imagine an event as occurring in the future, present, or past.

Constructive Episodic Simulation: Two Conceptual Issues 2. Constructive episodic simulation hypothesis emphasizes recombining of

Constructive Episodic Simulation: Two Conceptual Issues 2. Constructive episodic simulation hypothesis emphasizes recombining of details across events, but it is possible that subjects simply remember entire events and recast them in the future. In previous studies, future simulations could be based on recasting, recombining, or some combination of the two. Are main effects still observed when individuals are required to recombine elements of different episodes?

f. MRI Paradigm: Experimental Recombination of Details IMAGINE PAST MEMORY POOL IMAGINE FUTURE Imagine

f. MRI Paradigm: Experimental Recombination of Details IMAGINE PAST MEMORY POOL IMAGINE FUTURE Imagine PAST event: Fall outside library PERSON: Katie LOCATION: Widener OBJECT: Hat Imagine FUTURE event: Mom: Graduation Day Filipes: Meeting Cathy Gown: Graduation Day RECALL TASK Graduation Day PERSON: Mom LOCATION: Harvard Yard OBJECT: Gown RECALL memories: Cathy: Meeting Cathy Widener: Fall outside library Hat: Fall outside library Meeting Cathy PERSON: Cathy LOCATION: Filipes OBJECT: Fajita Katie: Fall outside library Harvard Yard: Graduation Day Fajita: Meeting Cathy CONTROL TASK CREATE SENTENCE Start with smallest: Cat: Include cat in sentence Bulb: Include bulb in sentence Tree: Include tree in sentence

f. MRI Paradigm: CONSTRUCTION CUE 0 2 RATE DETAIL ELABORATION RT 24 25 Imagine

f. MRI Paradigm: CONSTRUCTION CUE 0 2 RATE DETAIL ELABORATION RT 24 25 Imagine PAST event : Mom: Graduation Day Filipes: Meeting Cathy Gown: Graduation Day Button press when event is in mind RATE DETAIL 12345 Imagine FUTURE event : Katie: Fall outside library RATE DETAIL Harvard Yard: Graduation 12345 Fajita: Meeting Cathy Recall MEMORIES: Cathy: Meeting Cathy RATE DETAIL Widener: Fall outside library 12345 Hat: Fall outside library time

Experimental Recombination Task Common Core Network Future-Imagine, Past-Imagine & Past-Recall > Control Task Lateral

Experimental Recombination Task Common Core Network Future-Imagine, Past-Imagine & Past-Recall > Control Task Lateral temporal lobe Bilateral hippocampus Cuneus Retrosplenial / precuneus Medial prefrontal / frontal poles Lateral parietal lobe Retrosplenial / precuneus Addis, Pan, Vu, Laiser, & Schacter (in press, Neuropsychologia)

Experimental Recombination Task Imagining Subsystem? Future-Imagine and Past-Imagine > Control Task Lateral temporal lobe

Experimental Recombination Task Imagining Subsystem? Future-Imagine and Past-Imagine > Control Task Lateral temporal lobe Bilateral hippocampus Retrosplenial / precuneus Medial prefrontal / frontal poles Lateral parietal lobe Retrosplenial / precuneus

Experimental Recombination Task Remembering Subsystem? Past-Recall > Past-Imagine, Future-Imagine & Control Task Cuneus Middle/inferior

Experimental Recombination Task Remembering Subsystem? Past-Recall > Past-Imagine, Future-Imagine & Control Task Cuneus Middle/inferior occipital gyrus

Conclusions (see Schacter & Addis, 2009, Phil. Trans. Roy. Soc. ) • Constructive nature

Conclusions (see Schacter & Addis, 2009, Phil. Trans. Roy. Soc. ) • Constructive nature of the episodic memory system: during retrieval, various elements of past experiences are reintegrated and recombined, allowing us to draw on the past to imagine the future. • Imaging data support the constructive episodic simulation hypothesis - and the possibility that simulation of future events is a primary function of a constructive episodic memory. • The hippocampus plays an important role in recombining and encoding details from past episodes into simulations of the future. Converging evidence from work on prospective coding/preplay of event sequences.

Acknowledgements Memory Lab, Harvard Brendan Gaesser Kathy Gerlach Adrian Gilmore Yoko Okado Ling Pan

Acknowledgements Memory Lab, Harvard Brendan Gaesser Kathy Gerlach Adrian Gilmore Yoko Okado Ling Pan Jessica Payne Nathan Spreng Dale Stevens Gagan Wig Collaborators Donna Addis Randy Buckner Theresa Cheng Elizabeth Chua Noa Laiser Ling Pan Alana Wong Supported by NIMH & NIA