#10625 - Future Episodic Thinking 2 Lec 13 - Neuropsychology of Memory

Future Episodic Thinking (2)

What is the theoretical link between episodic memory & episodic future thinking?

• Narrative Ability

• Episodic Simulation Theory

• Scene Construction Theory

Narrative Ability

Race et al (2011)

• Investigated the nature + necessity of the MTL in imagining the future + tested the novel hypothesis that the MTL contributes to future thinking by supporting online binding processes related to narrative construction

• Amnesic patients with MTL damage + healthy controls constructed narratives about 1) future events, 2) past events, 3) visually presented pictures

• Measure mean no.of episodic details recorded

• All three tasks place similar demands on narrative construction - only past + future require memory/future episodic thinking to generate narrative construction

• Amnesic patients produced impoverished descriptions of both past + future events - BUT unimpaired at producing detailed picture narratives

• Future thinking performance positively correlated with episodic memory performance but did not correlated with narrative pic performance

• Arguably strong evidence that a common MTL mechanism supports both EM + EFT

• Ability to generate + maintain a detailed narrative is preserved in amnesia - suggests a common MTL mechanism supports both EM + E future thinking

• Argues against deficits in higher order processes related to narrative construction as the underlying cause of future thinking impairments in amnesia

Squire et al (2010) challenges view that EM + EFT rely on the same MTL mechanism

• Demonstrated that amnesic patients with MTL damage can imagine future events as well as controls

• Concluded that MTL not necessary for future thinking - prior reports of impaired future thinking in amnesia reflect neural damage outside the MTL

• HOWEVER Squire’s patients did not demonstrate pervasive autobiographical memory loss - suggests the extent of future thinking + memory impairments in amnesia may be related

• Fact that Race et al (2011)found pos correlation between EM + EFT => suggestive that a common MTL mechanism underlies both functions

EPISODIC SIMULATION THEORY Schacter & Addis (2007)

• EM is widely seen as a constructive process – rather than reproductive - process prone to various kinds of errors + illusions

• The constructive nature of EM is highly adaptive for performing a major function of this system to draw on past experiences in a way that allows us to imagine + simulate episodes which may occur in our personal future

• A number of researchers have recognised that information about past experiences is useful only to the extent that it allows us to anticipate what may happen in the future (Suddendorf & Busby, 2003) also Anderson & Schooler’s (1991) analysis of adaptive forgetting supports the idea that info about the past is retained when it is likely to be used in the future

• Future events are rarely exact replicas of past events - memory system which simply stored rote records of what happened in the past – would not be suited to stimulating future events

• Suggest a system built upon constructive principles is better suited to stimulating future happenings draw on elements of the past + retain the general sense of what has happened

• simulation related processes such as EM , future thinking + scene construction all require the extraction of relevant episodic details from memory + the recombination of these details for form fictitious simulations of novel scenes it is this process that depends on the integrity of the hippocampus

• One important function of retaining personal memories is that aspects of prev experienced events are used in envisioning future events in similar settings

• System can flexibly extract, recombine, + reassemble these elements in a way that allows us to stimulate , imagine or pre-experience events which have never occurred previously in the exact form we imagine them

• This theory endorses Suddendorf & Busby’s (2003) suggestion that “episodic reconstruction is just an adaptive feature of the future planning system”

• This is CONSTRUCTIVE EPSIODIC SIMUTLATION HYPOTHESIS

• For this theory to have merit then remembering the past + imaging the future should show a no of similar characteristics + depend on the same neural substrates

• Also suggests that the quality of future thinking will depend on the quality of the EM on which it is based

The importance of vivid + relevant memory are experienced as less vivid

• More remote memories have less perceptual details

• More distant future events are also less detailed + vivid

• e.g. if asked to imagine a holiday you would take next summer – this would be a more vivid representation that if asked to imagine a holiday you would take when you reach 60.

Szpunar & McDermott (2008)

• Hypothesised that if mental representations of the future as based upon the contents of memory - then the phenomenological quality of the episodic future thought should vary based on the contents of memory which have been sampled

• Future images based on recently experienced settings should be experienced as more vivid + associated with stronger subjective experience if they are based on more remote memories

• EXP 1 Ptp’s engaged in episodic future thought for events occurring within the next week either familiar (home) or novel (jungle) setting - expect ptps to have more vivid subjective exp’s when imaging events in a familiar context than novel setting

• Ptp’s used 7 point likert scales to rate the characterisitcs of the mental representations they had formed - sensorial details index

• EFT occurring in familiar settings was rated as having more sensorial detail + higher clarity of context - this may just be because familiar settings associated with more personal knowledge of what occurs within them – THIS LEAD TO EXP 2 TO CONTROL THIS DISCREPANCY

• EXP 2 varied extent to which familiar settings were characterised by perceptual detail

• Ptp asked to engage in episodic future thought - occurring in the next week in either a recently experience (Uni) OR remotely (high school) exp setting - settings exp on everyday basis – represented in greater perceptual detail than more remotely exp settings - therefore exp more vivid> - both settings ptp’s familiar with

• In comparison to remote settings, future images drawing upon recently exp settings were rated as having more sensorial detail - higher clarity of context + stronger subjective experience

• The extent to which ptp’s felt as though the pre-experienced a mental representation of the future varied positively with the quality of memorial information they were able to use to construct the representation

• Support for the constructive episodic simulation hypothesis the characteristics of memorial representations are preserved as they are projected into novel future scenarios

Addis & Schacter (2012)

• Neuropsychological + neuroimaging data appreas to support the idea that there are 3 important component processes involved in the simulation of episodic future events

1. Details stored in EM which aid the simulation must be accessed

2. Details extracted from various memories need to be recombined + integrated into a spatiotemporal context in order to input a simulation with a sense of coherence

3. If simulation is to influence + guide the future - it needs to be successfully encoded in memory

Evidence suggests these three components are reliant on the hippocampus - remains open questions as to whether diff sub regions of the hippo associated with each of these 3 processes

Evidence for differences between EM + EFT

• Okuda et al (2003) – great neural activity in frontopolar regions + the hippo when ptp’s imagined future events compared with past events

• Addis & Shacter (2008) – analysed the relation between neural activity + subjective ratings that ptp’s provided concerning amount of detail comprising past + future events

• Activity in the L posterior hippocampus was associated with the amount of detail compromising both past + future events - BUT L anterior hippocampus responsed selectively to the amount of detail comprising future events

Schacter & Addis – constructive episodic simulation hypothesis – attempts to accommodate for the discrepancies

• Finding of greater neural activity for future relative to past events - reflects more extensive construction processes required by imagining future events requires that details extracted from past experiences into the novel event

Why can EFT occur for completely novel settings e.g. in the jungle

• Irish et al (2012) – argued that stimulating novel future events - in contrast to remembering past events, relies on general conceptual knowledge that provides a scaffolding into which specific episodic details can be integrated

• Ptp’s may have used their semantic knowledge about jungles to envisage the novel environment of a jungle – hot + humid – take experience of this from EM + feed forward into future scenario

• Schacter & Addis (2012):

• Future episodic thinking can involve two processes

1. Gathering relevant material (episodic +_ semantic ) from memory

2. Flexibly recombining details from past events

• Suggestive of a potential role of semantic memory in construction of future imagined experiences doesn’t always have to rely on EM?

SCENE CONSTRUCTION THEORY

Hassabis & Maguire (2007)

• Retrieving + integrating perceptual, semantic + contextual info into a coherent spatial context

• More complex than simple visual imagery involves binding together disparate types of info into a coherent whole

• Scene construction not just limited to episodic memory of future...