Sophie E. Lind

Episodic memory and episodic future thinking in adults with autism.

The ability to remember past experiences (episodic memory) is thought to be related to the ability to imagine possible future experiences (episodic future thinking). Although previous research has established that individuals with autism spectrum disorder (ASD) have diminished episodic memory, episodic future thinking has not previously been investigated within this population. In the present study, high-functioning adults with ASD were compared to closely matched typical adults on a task requiring participants to report a series of events that happened to them in the past and a series of events that might happen to them in the future. For each event described, participants completed two modified Memory Characteristics Questionnaire items to assess self-reported phenomenal qualities associated with remembering and imagining, including self-perspective and degree of autonoetic awareness. Participants also completed letter, category, and ideational fluency tasks. Results indicated that participants with ASD recalled/imagined significantly fewer specific events than did comparison participants and that participants with ASD demonstrated impaired episodic memory and episodic future thinking. In line with this finding, participants with ASD were less likely than comparison participants to report taking a field (first-person) perspective and were more likely to report taking an observer (third-person) perspective during retrieval of past events (but not during simulation of future events), highlighting that they were less likely to mentally reexperience past events from their own point of view. There were no group differences in self-reported levels of autonoetic awareness or fluency task performance.

Memory and the self in autism: A review and theoretical framework

This article reviews research on (a) autobiographical episodic and semantic memory, (b) the self-reference effect, (c) memory for the actions of self versus other (the self-enactment effect), and (d) non-autobiographical episodic memory in autism spectrum disorder (ASD), and provides a theoretical framework to account for the bidirectional relationship between memory and the self in ASD. It is argued that individuals with ASD have diminished psychological self-knowledge (as a consequence of diagnostic social and communication impairments), alongside intact physical self-knowledge, resulting in an under-elaborated self-concept. Consequently, individuals with ASD show impaired autobiographical episodic memory and a reduced self-reference effect (which may each rely on psychological aspects of the self-concept) but do not show specific impairments in memory for their own rather than others’ actions (which may rely on physical aspects of the self-concept). However, it is also argued that memory impairments in ASD (e.g., in non-autobiographical episodic memory) may not be entirely accounted for in terms of self-related processes. Other factors, such as deficits in memory binding, may also play a role. Finally, it is argued that deficits in autobiographical episodic memory and future thinking may result in a diminished temporally extended self-concept in ASD.

Recognition Memory, Self-Other Source Memory, and Theory-of-Mind in Children with Autism Spectrum Disorder

This study investigated semantic and episodic memory in autism spectrum disorder (ASD), using a task which assessed recognition and self-other source memory. Children with ASD showed undiminished recognition memory but significantly diminished source memory, relative to age- and verbal ability-matched comparison children. Both children with and without ASD showed an “enactment effect”, demonstrating significantly better recognition and source memory for self-performed actions than other-person-performed actions. Within the comparison group, theory-of-mind (ToM) task performance was significantly correlated with source memory, specifically for other-person-performed actions (after statistically controlling for verbal ability). Within the ASD group, ToM task performance was not significantly correlated with source memory (after controlling for verbal ability). Possible explanations for these relations between source memory and ToM are considered.

Language and Theory of Mind in Autism Spectrum Disorder: The Relationship Between Complement Syntax and False Belief Task Performance

This study aimed to test the hypothesis that children with autism spectrum disorder (ASD) use their knowledge of complement syntax as a means of “hacking out” solutions to false belief tasks, despite lacking a representational theory of mind (ToM). Participants completed a “memory for complements” task, a measure of receptive vocabulary, and traditional location change and unexpected contents false belief tasks. Consistent with predictions, the correlation between complement syntax score and location change task performance was significantly stronger within the ASD group than within the comparison group. However, contrary to predictions, complement syntax score was not significantly correlated with unexpected contents task performance within either group. Possible explanations for this pattern of results are considered.

Episodic memory and episodic future thinking impairments in high-functioning autism spectrum disorder: an underlying difficulty with scene construction or self-projection?

Objective: There appears to be a common network of brain regions that underlie the ability to recall past personal experiences (episodic memory) and the ability to imagine possible future personal experiences (episodic future thinking). At the cognitive level, these abilities are thought to rely on “scene construction” (the ability to bind together multimodal elements of a scene in mind—dependent on hippocampal functioning) and temporal “self-projection” (the ability to mentally project oneself through time—dependent on prefrontal cortex functioning). Although autism spectrum disorder (ASD) is characterized by diminished episodic memory, it is unclear whether episodic future thinking is correspondingly impaired. Moreover, the underlying basis of such impairments (difficulties with scene construction, self-projection, or both) is yet to be established. The current study therefore aimed to elucidate these issues. Method: Twenty-seven intellectually high-functioning adults with ASD and 29 age- and IQ-matched neurotypical comparison adults were asked to describe (a) imagined atemporal, non-self-relevant fictitious scenes (assessing scene construction), (b) imagined plausible self-relevant future episodes (assessing episodic future thinking), and (c) recalled personally experienced past episodes (assessing episodic memory). Tests of narrative ability and theory of mind were also completed. Results: Performances of participants with ASD were significantly and equally diminished in each condition and, crucially, this diminution was independent of general narrative ability. Conclusions: Given that participants with ASD were impaired in the fictitious scene condition, which does not involve self-projection, we suggest the underlying difficulty with episodic memory/future thinking is one of scene construction.

Remembering the past and imagining the future in autism spectrum disorder

Recent research has revealed that episodic memory (remembering past experiences) and episodic future thinking (imagining future experiences) rely on the same underlying neuro-cognitive system. Consistent with this suggestion, individuals with autism spectrum disorder (ASD) have been shown to experience difficulties in both domains. In the present study 18 adults with ASD and 18 typical adults performed sentence completion tasks assessing the ability to generate past and future events. Contrary to previous research findings, results demonstrated that adults with ASD performed at an equivalent level to typical adults when generating both past and future events; generating a higher number of specific events when recalling past (relative to simulating future) events, and a higher number of semantic associates when simulating future (relative to recalling past) events. Results are discussed with respect to methodological factors affecting task performance in ASD including the social nature of the research, the need to verbalise memories to the experimenter, and whether or not the specific memory request is explicit.

Delayed self-recognition in children with autism spectrum disorder.

This study aimed to investigate temporally extended self-awareness (awareness of one’s place in and continued existence through time) in autism spectrum disorder (ASD), using the delayed self-recognition (DSR) paradigm (Povinelli et al., Child Development 67:1540–1554, 1996). Relative to age and verbal ability matched comparison children, children with ASD showed unattenuated performance on the DSR task, despite showing significant impairments in theory-of-mind task performance, and a reduced propensity to use personal pronouns to refer to themselves. The results may indicate intact temporally extended self-awareness in ASD. However, it may be that the DSR task is not an unambiguous measure of temporally extended self-awareness and it can be passed through strategies which do not require the possession of a temporally extended self-concept.

Spatial Navigation Impairments Among Intellectually High-Functioning Adults With Autism Spectrum Disorder: Exploring Relations With Theory of Mind, Episodic Memory, and Episodic Future Thinking

Research suggests that spatial navigation relies on the same neural network as episodic memory, episodic future thinking, and theory of mind (ToM). Such findings have stimulated theories (e.g., the scene construction and self-projection hypotheses) concerning possible common underlying cognitive capacities. Consistent with such theories, autism spectrum disorder (ASD) is characterized by concurrent impairments in episodic memory, episodic future thinking, and ToM. However, it is currently unclear whether spatial navigation is also impaired. Hence, ASD provides a test case for the scene construction and self-projection theories. The study of spatial navigation in ASD also provides a test of the extreme male brain theory of ASD, which predicts intact or superior navigation (purportedly a systemizing skill) performance among individuals with ASD. Thus, the aim of the current study was to establish whether spatial navigation in ASD is impaired, intact, or superior. Twenty-seven intellectually high-functioning adults with ASD and 28 sex-, age-, and IQ-matched neurotypical comparison adults completed the memory island virtual navigation task. Tests of episodic memory, episodic future thinking, and ToM were also completed. Participants with ASD showed significantly diminished performance on the memory island task, and performance was positively related to ToM and episodic memory, but not episodic future thinking. These results suggest that (contra the extreme male brain theory) individuals with ASD have impaired survey-based navigation skills—that is, difficulties generating cognitive maps of the environment—and adds weight to the idea that scene construction/self-projection are impaired in ASD. The theoretical and clinical implications of these results are discussed.

Time-based and event-based prospective memory in autism spectrum disorder: The roles of executive function and theory of mind, and time estimation

Prospective memory (remembering to carry out an action in the future) has been studied relatively little in ASD. We explored time-based (carry out an action at a pre-specified time) and event-based (carry out an action upon the occurrence of a pre-specified event) prospective memory, as well as possible cognitive correlates, among 21 intellectually high-functioning children with ASD, and 21 age- and IQ-matched neurotypical comparison children. We found impaired time-based, but undiminished event-based, prospective memory among children with ASD. In the ASD group, time-based prospective memory performance was associated significantly with diminished theory of mind, but not with diminished cognitive flexibility. There was no evidence that time-estimation ability contributed to time-based prospective memory impairment in ASD.

Diminished Time-Based, but Undiminished Event-Based, Prospective Memory Among Intellectually High-Functioning Adults With Autism Spectrum Disorder: Relation to Working Memory Ability

Objective: Prospective memory (PM) is the ability to remember to carry out an intended action. Working memory is the ability to store information in mind while processing potentially distracting information. The few previous studies of PM in autism spectrum disorder (ASD) have yielded inconsistent findings. Studies of working memory ability in ASD have suggested a selective impairment of “visual working memory.” However, it remains unclear whether any such impairment is the result of diminished (domain-specific; visual/verbal) storage capacity or diminished (domain-general) processing capacity. We aim to clarify these issues and explore the relation between PM and working memory in ASD. Method: Seventeen adults with ASD and 17 age- and IQ-matched comparison participants completed experimental measures of both event-based (perform action x when event y occurs) and time-based (perform action a at time b) PM, plus a self-report measure of PM skills. Participants also completed a working memory test battery. Results: Participants with ASD self-reported diminished PM skill, and showed diminished performance on the time-based, but not event-based, PM task. On the working memory test battery, visual but not verbal storage capacity was diminished among participants with ASD, as was processing ability. Whereas visual storage was associated with event-based PM task performance among comparison participants, verbal storage was associated among ASD participants. Conclusions: ASD appears to involve a selective deficit in time-based PM and a selective difficulty with aspects of working memory that depend on the storage of visual information. However, event-based PM may be achieved through compensatory strategies in ASD.