Episodic Autobiographical Memory, Time Perception and Self-Awareness in ASC

Background: Recent research has suggested individuals with ASC have a specific episodic memory deficit with preserved semantic memory functioning. Cognitive capacities such as self-awareness and subjective time perception are considered to play important roles in episodic memory. Studies have shown abnormalities in both these areas in ASC (e.g. Hurlburt, Happe et al. 1994; Szelag et al. 2004), however no study has yet investigated the relationship between these abnormalities and the episodic memory impairment reported in ASC.

Objectives: The purpose of this research is to investigate episodic autobiographical memory in ASD using both a quantitative measure and a qualitative measure. We then investigate reflective self-awareness and subjective time perception.

Methods: The performance of children with ASC (n = 16) on a quantitative (fluency) and a qualitative (interview) measure of episodic and semantic autobiographical memory was compared to that of typically developing children matched for IQ, generativity and verbal fluency. Their performance on a retrospective time reproduction task (using durations between 500ms and 45s) and a self-awareness task requiring reflection on own knowledge was also measured.

Results: The quantitative memory measures revealed that the children with ASC reported significantly fewer episodic autobiographical memories than typically-developing children. Conversely, there was no difference in the quantity of semantic autobiographical memories recalled between the two groups.

In the timing test, the children with ASC were significantly less accurate in reproducing temporal durations than the comparison group, both at short durations of 500-2000ms (thought to involve attentional processes) and at longer durations of 30-45s (thought to involve long-term memory, in particular the episodic system).

In the reflective self-awareness measure, the ASC group was significantly less accurate in reporting the strength of their knowledge and in differentiating between knowing and guessing. The group also showed a lower correlation between strength of knowledge and the level of confidence in that knowledge than the comparison group.

Conclusions: We conclude that ASC children recall fewer episodic autobiographical memories than comparison children, despite showing no difference in their semantic autobiographical memory recall. In addition, they show time perception and self-awareness abnormalities, which may be correlated with their episodic memory deficits.