Does Inhibitory Load Affect Event-Based Prospective Memory Performance in Autism Spectrum Disorder?

Background:  

Previous evidence indicates that individuals with Autism Spectrum Disorders (ASD) have difficulties with the implementation of delayed intentions. These deficits in prospective memory performance have been related to reduced executive functioning. So far, however, apart from correlational approaches, the impact of executive control processes on prospective memory performance have not been directly tested.  

Objectives:  

The goal of the present study was to explore the influence of inhibitory control processes on event-based prospective memory performance in adults with ASD. 

Methods:  

Twenty individuals with ASD and 20 age-, verbal and nonverbal ability-matched typically developing controls participated in the present study. Participants were asked to perform a prospective memory task which was embedded in a word categorization task (ongoing activity). Inhibitory load was manipulated by an auditory mediated Go/No-Go task with either low or high inhibitory load. Participants were first introduced to the ongoing task. This was followed by an introduction to the  inhibition task (low or high inhibition load). Thereafter, individuals completed the inhibition task and the ongoing task simultaneously. Then participants were introduced to the prospective memory task and after a filled delay performed all three tasks simultaneously. Order of inhibition load condition was balanced and this procedure repeated (except for the introduction of the ongoing task) after a short break for the respective other inhibition load condition. 

Results:  

Repeated measures Analyses of Variance (ANOVAs) were carried out. With regards to prospective memory performance, there were no significant effects. In contrast for ongoing task performance, significant effects were observed for group and task block. Controls outperformed individuals with ASD and overall, participants performed poorer with each additional task being added (best performance in the single task block, followed by dual-task blocks and triple task blocks). No significant interaction emerged. Similarly, for the inhibition task performance was best in the single task blocks, followed by the dual task and then triple task blocks. No group effects and no interaction effects were found. 

Conclusions:  

In line with previous evidence in children with ASD (Altgassen et al., 2010), adults with ASD showed preserved prospective memory performance. However, possibly this spared performance may have only been achieved at the cost of the ongoing task in which individuals with ASD performed poorer as compared to controls. There were no differential effects of inhibitory load. Findings are limited by ceiling effects of both groups in the inhibition task. Future studies need to try to replicate findings using more difficult tasks.