Effects of NREM sleep instability on cognitive processing

Objective: Cyclic alternating pattern (CAP) A1 subtypes, characterized by high-voltage slow waves, are generated by the frontal cortex and are suspected to have a role in cognitive processing during NREM sleep. Conversely, CAP A2 and A3 subtypes are characterized by variable amounts of rapid EEG potentials arising from the parietal-occipital areas and often coincide with arousals. We tested the hypothesis that CAP subtypes differentially correlate with cognitive functions. Subjects and methods: Eight healthy participants were recruited. Two nocturnal polysomnography studies and a series of neuropsychological tests were obtained in the subjects during the morning and afternoon of the first day and on the morning of the second day. Results: In agreement with our original hypothesis, we found that CAP A1 subtypes were correlated with better neuropsychological functioning the day after, for verbal fluency, working memory, and both delayed recall and recognition of words. These same neuropsychological test results were found to be negatively correlated with CAP A2 subtypes. CAP A3 subtypes were negatively correlated with the Trial Making test Parts A and B. Conclusions: The results suggest that CAP A1 might be related to better cognitive functioning, whereas CAP A2 and A3 correlated with worse cognitive functioning. Further studies are needed to better understand how CAP influences cognitive performance, especially frontally-dependent functions and memory.