Effects of Breathing and Breath-hold on Brain Functional Connectivity

Recent years have seen a wealth of literature increasingly recognizing the concept that breathing rhythms entrain the activity of the human brain. However, the mechanisms underlying this phenomenon, and the extent to which rhythmic brain activity is modulated by breathing are not fully understood at the moment. The study reported herein is a preliminary step towards that goal. The variations in the electroencephalogram (EEG) based functional connectivity (FC) of the human brain during normal breathing, and voluntary breath-hold has been investigated and reported here. An experimental protocol involving breathing and breath-hold sessions, synchronized to a visual-metronome was designed and administered on 20 healthy subjects (9 females and 11 males within a range of 23–60 years). EEG data were collected from all subjects during breathing and breath-hold sessions using the 64 channel eego™mylab system from ANT Neuro. Further, FC was estimated on brain hemispheres and 7 cortical regions for 5 specific EEG bands, and variations were examined statistically. The observations illustrated that the brain FC exhibits a hemispherical symmetry during breath-hold in the delta and alpha bands. Synchronization of neuronal assemblies in different cortical regions of the brain was found to be higher in low-frequency EEG bands and lower in high-frequency EEG bands. Furthermore, the study also revealed that gamma-band FC of the pre-frontal cortex could distinctly identify an inhale-hold from exhale-hold.