Prospective Memory in ASD

Prospective Memory (PM or ProM- I’ll be using the term PM) is defined as a number of functions that enable a person to carry out an intended act after a delay (Burgess et al., 2001). A significant number (50–80%) of all everyday memory problems are, at least in part, PM problems (Kliegel & Martin, 2003). However, PM is one of the least studied forms of memory in cognitive neuroscience.

PM is divided into a retrospective and a prospective component (Einstein & McDaniel, 1990). The retrospective component involves the retention of the action to be performed and the prospective entails the retrieval of the action, after the identification of the encoded cue. Both frontal lobe areas and the medial temporal lobes (MTL) are thought to play a role in PM. One area constantly associated with PM tasks from various lesions and neuroimaging studies (Simons et al., 2006; Miller & Cohen, 2001) is the frontopolar and superior rostral aspects of the frontal lobes (approximating BA10).

A number of cognitive abilities that have been associated with rostral PFC seem to be impaired in ASD (Hill, 2004; also see older post on Executive Functions in ASD.)

Even though evidence suggests that PM could be impaired in ASD, only a limited number of studies have been done to examine this. Mackinlay et al. (2006) investigated PM in children with ASD and found that they had difficulties in planning, carrying out and switching between different tasks.

Recently, Altgassen et al. (2009) found reduced performance in ASD as compared to controls in a time-based PM task and that was attributed to poor task monitoring and task organization. Monitoring, like many executive functions, also is associated with frontal lobe function (Shallice & Burgess, 1991).

Only one study (Altgassen et al., 2009b) has looked into event-based PM on children with ASD. The participants were 19 high-functioning children and adolescents with ASD and 19 typically developing controls. They were asked to work simultaneously on an ongoing and a PM task. The ongoing task was a visuo-spatial working memory task and for the PM task, they were to press the certain key whenever the background colour of the screen changed to yellow. Dependent measures were accuracy and reaction times. They also measured subjective everyday executive functioning by using The DEX questionnaire, which was filled by the parents of the subjects. No significant differences were found between the two groups in any of the measures apart from the subjective everyday ratings. The parents of the participants with ASD rated their children’s performance as poorer than controls’ parents.

Here’s the explanation that Altgassen et al. (2009b) give about the deficits found in time-based PM, but not in event-based PM:

…in comparison to time-based tasks or complex multitasking paradigms simple, event-based PM tasks are very structured, and similarly to cued (retrospective) recall provide (here: visual) cues that may support retrieval of the intended action and put lower demands on self-initiated strategy application which may decrease executive control demands and thus enable individuals with ASD to preserved event-based PM
performance [23]…

Interestingly, studies show that people with ASD seem to have deficits mostly in ill-structured tasks, while they perform near or at control levels at well-structured tests (White et al., 2009). In this paper

the ASD group tended to create fewer spontaneous strategies and exhibit more idiosyncratic behavior, which particularly disadvantaged them on the more open-ended tasks.

It would be very interesting to see if future studies will replicate Altgassen et al.’s results using a bigger sample or a more difficult task requiring higher working memory load.

Altgassen, M., Schmitz-Hübsch, M., & Kliegel, M. (2009). Event-based prospective memory performance in autism spectrum disorder Journal of Neurodevelopmental Disorders, 2 (1), 2-8 DOI: 10.1007/s11689-009-9030-y

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