P.P. Ujma Semmelweis University, Budapest, Hungary
Keywords: sleep; IQ; intelligence; sleep spindle; electroencephalography; circadian rhythm; sleep efficiency.
Introduction. General cognitive ability or intelligence and sleep may be correlated through both biological and social mechanisms. The relationship between intelligence and sleep macro- and microstructure has been extensively studied.
Results. Based on meta-analyses and large samples [1; 2] a small positive association exists between IQ and eveningness and sleep efficiency. The direction of these effects, however, is not clear, and they may not be stable across all ages. Sleep microstructural elements, such as EEG oscillations are even more promising biomarkers due to their trait-like nature and the fact that they reflect brain activity in a state where the conscious processing of environmental stimuli is least prominent. The amplitude of sleep spindles, thalamocortical oscillations in NREM sleep, is positively associated with IQ. Other positive associations in the literature have a poor replication record .
Conclusion. The study of sleep oscillations still holds much promise for clarifying the neural mechanisms supporting IQ. I highlight three main problems which require further work: 1) some findings in the literature may be false positives due to considerable researcher degrees of freedom, while poor methodology may have resulted false negatives; 2) the association between IQ and sleep oscillations other than spindles is understudied and 3) the use of multi-test IQ batteries and confirmatory factor analysis is rare in the field, and for this reason it is unknown if sleep oscillations are related to general or specific cognitive abilities.
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