Abstract
Sigma power during sleep is associated with cognitive abilities in healthy humans. We examined the relationship between sigma power in sleep EEG and intelligence and alertness in schoolchildren with ADHD (n = 17) in comparison to mentally healthy children (n = 16) and adults (n = 23). We observed a positive correlation between sigma power in sleep stage 2 and IQ in healthy adults but a negative correlation in children with ADHD. Furthermore, children with ADHD showed slower reaction times in alertness testing than both control groups. In contrast, only healthy children displayed a positive correlation between sigma power and reaction times. These data suggest that the associations between sigma power and cognitive performance underlie distinct developmental processes. A negative association between IQ and sigma power indicates a disturbed function of sleep in cognitive functions in ADHD, whereas the function of sleep appears to be matured early in case of motor-related alertness performance.
Highlights
Sleep is essential for optimal cognitive performance such as alertness, working memory, or IQ performance [1,2,3,4]
Note: Attention-deficit/hyperactivity disorder (ADHD), attention-deficit hyperactivity disorder; healthy male children (HC), healthy children; HA, healthy adults; RT, reaction times; sleep parameters: Time in bed (TIB), time in bed; TST, total sleep time; SE, sleep efficiency; S1-4, sleep stages 1–4; rapid-eve movement (REM), rapid-eye-movement; SD, standard deviation; analysis of variances (ANOVA), analysis of variance; bold values indicate survival of a Bonferroni-corrected significance level of p < .0083 (0.05/6) chosen for all sleep parameters; see S3 Table for statistical values of all group-wise comparisons of single means
The analysis of alertness revealed a main effect for GROUP [F(2,53) = 28.7, p < .001], showing that children with ADHD had prolonged RT compared to HC [t(31) = 2.26, p = .031] and healthy adults [t(38) = 6.92, p < .001)
Summary
Sleep is essential for optimal cognitive performance such as alertness, working memory, or IQ performance [1,2,3,4]. Sleep is usually understood as being a state that can be disturbed, and sleep quality can change from one day to the other depending on many different factors [5]. Sleep quality can significantly influence cognitive performance in children and adults, only little is known about a state-independent relationship between sleep and cognitive functions in terms of an individual trait. There is increasing evidence that sleep spindle or sigma activity can predict state-independent cognitive functions such as IQ performances in healthy adults Studies on the relationship between sigma activity and cognitive performance with respect to brain maturation, are clearly underrepresented.
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