Exploring brain functional connectivity in rest and sleep states: a fNIRS study

Area of Science:

• Neuroscience
• Cognitive Science
• Biomedical Engineering

Background:

• Understanding brain functional connectivity is crucial for studying cognitive states like rest and sleep.
• Simultaneous electroencephalography (EEG), electrooculography (EOG), and functional near-infrared spectroscopy (fNIRS) offer a multimodal approach to investigate brain activity.

Purpose of the Study:

• To investigate brain functional connectivity across different rest and sleep states using simultaneous EEG, EOG, and fNIRS.
• To evaluate the potential of fNIRS as a primary tool for studying brain connectivity during rest and sleep.

Main Methods:

• Collected simultaneous EEG, EOG, and fNIRS signals during quiet wake-eyes open (w_o), quiet wake-eyes closed (w_c), non-rapid eye movement sleep stage 1 (N1), and stage 2 (N2) states.
• Calculated cerebral hemodynamic responses (oxy-, deoxy-, and total hemoglobin) from fNIRS signals.
• Computed network connectivity using Pearson correlation coefficients of hemodynamic responses across 15 brain networks derived from 133 fNIRS channels grouped into five regions.

Main Results:

• The connection ratio was higher in the w_c and N1 states compared to w_o and N2 states across all networks and hemoglobin types.
• Connection strength was similar between w_c and N1 states, and lower in w_o and N2 states.
• fNIRS demonstrated high potential for studying brain connectivity in rest and sleep states.

Conclusions:

• Brain functional connectivity patterns differ significantly across wake and sleep stages.
• fNIRS is a promising tool for non-invasive assessment of brain connectivity during various physiological states, including sleep.
• The findings provide valuable insights into the dynamic changes in brain networks during the transition from wakefulness to sleep.