Reconfigurations in brain networks upon awakening from slow wave sleep: Interventions and implications in neural communication

The Awakening Brain is Characterized by a Widespread and Spatiotemporally Heterogeneous Increase in High Frequencies

Morning awakening is part of everyday life. Surprisingly, information remains scarce on its underlying neurophysiological correlates. Here simultaneous polysomnography and stereo-electroencephalography recordings from 18 patients are used to assess the spectral and connectivity content of the process of awakening at a local level 15 min before and after the awakening. Awakenings from non-rapid eye movement sleep are accompanied by a widespread increase in ripple (>80 Hz) power in the fronto-temporal and parieto-insular regions, with connectivity showing an almost exclusive increase in the ripple band in the somatomotor, default, dorsal attention, and frontoparietal networks. Awakenings from rapid eye movement sleep are characterized by a widespread and almost exclusive increase in the ripple band in all available brain lobes, and connectivity increases mainly in the low ripple band in the limbic system as well as the default, dorsal attention, somatomotor, and frontoparietal networks.

[Impairments in sustained attention and the efficiency of psychomotor activity during episodes of spontaneous awakening from daytime sleep]

OBJECTIVE

To study attention span (vigilance) disorders and identify their objective characteristics in a sleep inertia state after spontaneous awakening from daytime sleep.

MATERIAL AND METHODS

In 15 healthy subjects (students), a bimanual psychomotor test was used to analyze attention span disorders after waking up from the stage 2 of daytime sleep. The number of button presses with the right and left hands was used to assess the disorders: compliant and non-compliant (a smaller number) with the instruction. Attention was considered impaired if a subject did not fully follow the test instructions. Complete test was considered as a behavioral marker of no impairment. The power characteristics of electroencephalography (EEG), which was recorded with different attention span in a subject, were analyzed.

RESULTS

Attention span (vigilance) disorders upon awakening in the sleep inertia state are accompanied by generalized higher power of slow wave activity and lower power of the low-frequency alpha rhythm. These findings indicate differences in brain activation that impair the subjects' attention span in this state. The attention span does not affect the psychomotor activity switching from one hand to the other. Of note, the control over the instruction-based number of presses during switching in subjects who completed the test requires more brain resources, which is reflected in an increase in the gamma rhythm power during the test.

CONCLUSION

The detected neurocorrelates of impaired attention span (vigilance) due to the awakening state helps to create a set of markers that can be used to optimize the sleep-wake cycle in case of restrictions and shifts in the sleep period. They can also be used in clinical practice when patients complain of cognitive impairment due to sleep disorders.

The Effect of Sleep Deprivation on Brain Fingerprint Stability: A Magnetoencephalography Validation Study

This study examined the stability of the functional connectome (FC) over time using fingerprint analysis in healthy subjects. Additionally, it investigated how a specific stressor, namely sleep deprivation, affects individuals' differentiation. To this aim, 23 healthy young adults underwent magnetoencephalography (MEG) recording at three equally spaced time points within 24 h: 9 a.m., 9 p.m., and 9 a.m. of the following day after a night of sleep deprivation. The findings indicate that the differentiation was stable from morning to evening in all frequency bands, except in the delta band. However, after a night of sleep deprivation, the stability of the FCs was reduced. Consistent with this observation, the reduced differentiation following sleep deprivation was found to be negatively correlated with the effort perceived by participants in completing the cognitive task during sleep deprivation. This correlation suggests that individuals with less stable connectomes following sleep deprivation experienced greater difficulty in performing cognitive tasks, reflecting increased effort.