Patterns of Interhemisphere Interactions on Waking from Brief Episodes of Daytime Sleep

Our previous studies using data on multiple fallings asleep while performing a bimanual psychomotor test with a mobile app on a smartphone identified and interpreted four qualitatively different patterns of behavioral activity in interhemispheric interactions during falling asleep. Additional studies in the same 73 students consisted of 191-hour experiments whose data were analyzed to identify changes in interhemispheric interactions on waking from sleep. Analysis using the Ward hierarchical clustering method identified four clusters. Mean values of behavioral indicators in these clusters were estimated and two sets of clusters were compared using the Pearson χ2 test. A marked pattern of asymmetry between the hands was very rare; the least “sleepy” cluster was characterized by alternation of the hands on awakening, while the most “sleepy” cluster was characterized by less predictability of patterns over time. The results also showed that that the “asymmetric” and “sleepy” clusters never replaced each other between falling asleep and waking up and were more often replaced by the remaining two clusters than vice versa. These results may reflect the dynamics of interhemispheric interactions during transitions between sleep and waking. It is suggested that between-cluster differences are due to the characteristic features of restructuring of the functional connectivity of the brain in different ranges of EEG activity. © 2025 Elsevier B.V., All rights reserved.