Sleep Dependent Memory Consolidation in Children with Autism Spectrum Disorder

Abstract

Study objectives: Examine the role of sleep in the consolidation of declarative memory in children with autism spectrum disorder (ASD).

Design: Case-control study.

Setting: Home-based study with sleep and wake conditions.

Participants: Twenty-two participants with ASD and 20 control participants between 9 and 16 y of age.

Measurements and results: Participants were trained to criterion on a spatial declarative memory task and then given a cued recall test. Retest occurred after a period of daytime wake (Wake) or a night of sleep (Sleep) with home-based polysomnography; Wake and Sleep conditions were counterbalanced. Children with ASD had poorer sleep efficiency than controls, but other sleep macroarchitectural and microarchitectural measures were comparable after controlling for age and medication use. Both groups demonstrated better memory consolidation across Sleep than Wake, although participants with ASD had poorer overall memory consolidation than controls. There was no interaction between group and condition. The change in performance across sleep, independent of medication and age, showed no significant relationships with any specific sleep parameters other than total sleep time and showed a trend toward less forgetting in the control group.

Conclusion: This study shows that despite their more disturbed sleep quality, children with autism spectrum disorder (ASD) still demonstrate more stable memory consolidation across sleep than in wake conditions. The findings support the importance of sleep for stabilizing memory in children with and without neurodevelopmental disabilities. Our results suggest that improving sleep quality in children with ASD could have direct benefits to improving their overall cognitive functioning.

Keywords: autism spectrum disorder; children; cognition; memory consolidation; sleep.

Figure 1

Study protocol. (A) Timeline. Comparison of Test to Retest reflects sleep dependent memory consolidation in the Sleep condition, and memory consolidation during an equivalent period of wakefulness in the Wake condition. (B) Screen displays. 1. During the exposure phase, the spatial locations of each card pair is displayed, one pair at a time. 2. During the training phase, one item is presented to participants and they are asked to click on to the matching card; here, the participant selects the wrong card (as indicated by an “X” over its back), and the correct location of the matching card is displayed (feedback). This phase continues until the participant reached 40% accuracy. 3. Immediately after the training phase, participants are tested. The participants are again shown an item and asked to select the correct location of the matching card. In this phase, feedback is not provided. Delayed recall was tested after a period of wake or sleep.

Figure 2

Raw data on number of trial trials to criterion and Immediate recall scores for the ASD and TD groups. (A) ASD participants required more trials to reach criterion compared to controls (P = 0.03) but there was no main effect of time of testing (morning versus evening), P = 0.47. (B) Likewise, participants in the ASD group demonstrated poorer immediate recall (testing immediately after training) in both the morning and evening conditions compared to controls (P < 0.001). No circadian effects of learning were detected (main effect of time of testing, P = 0.58). Error bars represent standard error of mean. ASD, autism spectrum disorder; TD, typically developing.

Figure 3

Memory consolidation across sleep and wake intervals for ASD and TD participants. Error bars represent standard error of means. A mixed effects model adjusting for age, nonverbal IQ, and sex revealed that participants' showed significantly less forgetting over periods of sleep than wake across groups (main effect for condition, P = 0.01). Participants with ASD demonstrated more forgetting across conditions than controls (main effect for group, P = 0.049). No group × condition interaction was detected. ASD, autism spectrum disorder; TD, typically developing.

Figure 4

Group correlations between total sleep time and change in recall accuracy on task after sleep. There was a significant correlation between sleep duration and overnight task improvement in the control group (●) but not in the ASD group (▲).