# Decline of long-range temporal correlations in the human brain during sustained wakefulness

## TL;DR

This study shows that long-range temporal correlations in human brain activity decrease during extended wakefulness, highlighting sleep's role in maintaining optimal cortical network dynamics for cognitive functions.

## Contribution

It provides empirical evidence that sleep deprivation reduces LRTCs in EEG signals, supporting the hypothesis that sleep reorganizes brain networks towards criticality.

## Key findings

- LRTCs decline with increased sleep deprivation
- Decline in LRTCs correlates with reduced cognitive performance
- Sleep helps maintain critical brain dynamics

## Abstract

Sleep is crucial for daytime functioning, cognitive performance and general well-being. These aspects of daily life are known to be impaired after extended wake, yet, the underlying neuronal correlates have been difficult to identify. Accumulating evidence suggests that normal functioning of the brain is characterized by long-range temporal correlations (LRTCs) in cortex, which are supportive for decision-making and working memory tasks. Here we assess LRTCs in resting state human EEG data during a 40-hour sleep deprivation experiment by evaluating the decay in autocorrelation and the scaling exponent of the detrended fluctuation analysis from EEG amplitude fluctuations. We find with both measures that LRTCs decline as sleep deprivation progresses. This decline becomes evident when taking changes in signal power into appropriate consideration. Our results demonstrate the importance of sleep to maintain LRTCs in the human brain. In complex networks, LRTCs naturally emerge in the vicinity of a critical state. The observation of declining LRTCs during wake thus provides additional support for our hypothesis that sleep reorganizes cortical networks towards critical dynamics for optimal functioning.