Wake EEG Coherence before and after Sleep in Adults with Autism: Decreased Morning Frontal Connectivity

Background:  Autism is a neurodeveloppemental disorder characterized by atypical connectivity between brain regions. People with autism are known to have sleep disorders.

Objectives: The purpose of this study was to analyze brain connectivity before and after a night of sleep using EEG coherence analysis.

Methods: Nine adults with autism (21.1 ± 4.0 years) and 20 control participants (20.8 ± 4.2 years) were recorded for two consecutive nights in a sleep laboratory, using a 22-electrode montage. Every participant had a normal IQ and none were taking medication. Wake EEG was recorded for 5 minutes at bedtime and just before final rise time in the morning, while lying in bed with eyes closed. EEG coherence values were compared with a multivariate repeated measures design using Group x Moment x Frequency band factors for each electrode separately, followed by post hoc tests. 

Results: In the evening, the autistic group displayed more Alpha coherence than controls within the left visual area (P3-O1: p=0.049; T5-O1: p=0.03 and T5-P3: p=0.014). In the morning more Alpha coherence in the autistic group within the left visual area was also measured (T5-O1: p=0.009 and T5-P3: p=0.015) as well as more Delta coherence at the T5-O1 electrode pair (p=.027). Moreover, morning recordings showed less Delta coherence within the right frontal area, (Fp2-F8: p=0.037; F4-F8: p=0.011) and between left and right hemispheres (F3-F4: p=0.019; F7-F8: p=0.003).

Conclusions: A previous study performed during REM sleep (Léveillé et al., 2010) found a greater intrahemispheric EEG coherence in autistic participants compared to controls between the left visual cortex and regions either close to or distant from it. The present results are in the same direction, upon both evening and morning wake recordings, suggesting that sleep per se is not responsible for these signs of overconnectivity. The present results also revealed a morning specific lower EEG coherence values for slow frequencies in the right frontal area in participants with autism compared to controls, suggesting that sleep per se could be responsible for these signs of underconnectivity.