NREM sleep EEG activity and procedural memory: A comparison between young neurotypical and autistic adults without sleep complaints

Abstract

Delta EEG activity (0.75-3.75 Hz) during non-Rapid eye movement (NREM) sleep reflects the thalamo-cortical system contribution to memory consolidation. The functional integrity of this system is thought to be compromised in the Autism spectrum disorder (ASD). This lead us to investigate the topography of NREM sleep Delta EEG activity in young adults with ASD and typically-developed individuals (TYP). The relationship between Delta EEG activity and sensory-motor procedural information was also examined using a rotary pursuit task. Two dependent variables were computed: a learning index (performance increase across trials) and a performance index (average performance for all trials). The ASD group showed less Delta EEG activity during NREM sleep over the parieto-occipital recording sites compared to the TYP group. Delta EEG activity dropped more abruptly from frontal to posterior regions in the ASD group. Both groups of participants learned the task at a similar rate but the ASD group performed less well in terms of contact time with the target. Delta EEG activity during NREM sleep, especially during stage 2, correlated positively with the learning index for electrodes located all over the cortex in the TYP group, but only in the frontal region in the ASD group. Delta EEG activity, especially during stage 2, correlated positively with the performance index, but in the ASD group only. These results reveal an atypical thalamo-cortical functioning over the parieto-occipital region in ASD. They also point toward an atypical relationship between the frontal area and the encoding of sensory-motor procedural memory in ASD. Autism Res 2018, 11: 613-623. © 2018 International Society for Autism Research, Wiley Periodicals, Inc.

Lay summary: Slow EEG waves recorded from the scalp during sleep are thought to facilitate learning and memory during daytime. We compared these EEG waves in young autistic adults to typically-developing young adults. We found less slow EEG waves in the ASD group and the pattern of relationship with memory differed between groups. This suggests atypicalities in the way sleep mechanisms are associated with learning and performance in a sensory-motor procedural memory task in ASD individuals.

Keywords: EEG; autism; autism spectrum disorder; delta activity; learning; memory; procedural memory; sleep.