Breath-hold task induces temporal heterogeneity in electroencephalographic regional field power in healthy subjects

We demonstrated that changes in CO2 values cause oscillations in the cortical activity in d-and a-bands. The analysis of the regional field power (RFP) showed evidence that different cortical areas respond with different time delays to CO2 challenges. An opposite behavior was found for the end-tidal O2. We suppose that the different cortical time delays likely expresse specific ascending pathways to the cortex, generated by chemoreceptor nuclei in the brain stem. Although the brain stem is in charge of the automatic control of ventilation, the cortex is involved in the voluntary control of breathing but also receives inputs from the brain stem, which influences the perception of breathing, the arousal state and sleep architecture in conditions of hypoxia/hypercapnia. We evaluated in 11 healthy subjects the effects of breath hold (BH; 30 s of apneas and 30 s of normal breathing) and BH-related CO2/O2 changes on electroencephalogram (EEG) global field power (GFP) and RFP in nine different areas (3 rostrocaudal sections: anterior, central, and posterior; and 3 sagittal sections: left, middle, and right) in the d- and a-bands by cross correlation analysis. No significant differences were observed in GFP or RFP when comparing free breathing (FB) with the BH task. Within the BH task, the shift from apnea to normal ventilation was accompanied by an increase in the d-power and a decrease in the a-power. The end-tidal pressure of CO2 (PETCO2 ) was positively correlated with the d-band and negatively with the a- band with a positive time shift, whereas an opposite behavior was found for the end-tidal pressure of O2 (PETO2 ). Notably, the time shift between PETCO2 / PETO2 signals and cortical activity at RFP was heterogenous and seemed to follow a hierarchical activation, with the d-band responding earlier than the a-band. Overall, these findings suggest that the effect of BH on the cortex may follow specific ascending pathways from the brain stem and be related to chemoreflex stimulation. NEW & NOTEWORTHY We demonstrated that the end tidal CO2 oscillation causes oscillations of delta and alpha bands. The analysis of the regional field power showed that different cortical areas respond with different time delays to CO2 challenges. An opposite behavior was found for the end-tidal O2. We can suppose that the different cortical time delay response likely expresses specific ascending pathways to the cortex generated by chemoreceptor nuclei in the brainstem.