Differential effects of slow deep inhalation and exhalation on brain functional connectivity

Slow conscious breathing is an integral aspect of many therapeutic techniques due to its relaxing effects. While the neuroscience of conscious breathing has been explored widely, the exact neural mechanisms linking slow breathing to its therapeutic effects are still debated. This work utilizes electroencephalography (EEG) to identify functional connections specific to the inhalation and exhalation phases of slow deep breathing at 2 cycles per minute. EEG data were collected from 20 healthy participants using the 61-channel eego
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mylab system from ANT Neuro. Functional connectivity (FC) for all possible pairs of EEG time series data was estimated using the phase slope index, for 7 EEG bands. Further, feature selection and classification were performed to identify functional connections that could effectively distinguish the inhale from the exhale phase of the respiratory cycle. The best accuracy of 99.08% was obtained when 340 low gamma-band functional connections were fed as input to a support vector machine with radial basis function kernel. Furthermore, the inter- and intra-cortical distribution of these functional connections was explored based on the topographical grouping of EEG electrodes. It was observed that most of the statistically significant connections were within central or between central and parieto-occipital regions of the brain.