Analysis of generic coupling between EEG activity and PETCO2 in free breathing and breath-hold tasks using Maximal Information Coefficient (MIC)

Maria Sole Morelli,Nicola Vanello,Alberto Giannoni,Gaetano Valenza,Michele Emdin,Enzo Pasquale Scilingo,Alberto Greco

doi:10.1038/s41598-018-22573-6

Abstract

Brain activations related to the control of breathing are not completely known. The respiratory system is a non-linear system. However, the relationship between neural and respiratory dynamics is usually estimated through linear correlation measures, completely neglecting possible underlying nonlinear interactions. This study evaluate the linear and nonlinear coupling between electroencephalographic (EEG) signal and variations in carbon dioxide (CO2) signal related to different breathing task. During a free breathing and a voluntary breath hold tasks, the coupling between EEG power in nine different brain regions in delta (1–3 Hz) and alpha (8–13 Hz) bands and end-tidal CO2 (PET CO2) was evaluated. Specifically, the generic associations (i.e. linear and nonlinear correlations) and a “pure” nonlinear correlations were evaluated using the maximum information coefficient (MIC) and MIC-ρ2 between the two signals, respectively (where ρ2 represents the Pearson’s correlation coefficient). Our results show that in delta band, MIC indexes discriminate the two tasks in several regions, while in alpha band the same behaviour is observed for MIC-ρ2, suggesting a generic coupling between delta EEG power and PETCO2 and a pure nonlinear interaction between alpha EEG power and PETCO2. Moreover, higher indexes values were found for breath hold task respect to free breathing.

Highlights

(EEG) signal and variations in carbon dioxide (CO2) signal related to different breathing task
The Maximal Information Coefficient (MIC) increased during the breath hold (BH) task, and, in particular, the higher increase was found in the middle-right anterior (MA and RA) regions and the middle-left central (MC and LC) regions
The nonlinear correlation between EEG power and PETCO2 significantly increased during the BH task in the middle anterior (MA) area for both bandwidths and in the whole anterior brain area, as well as in the right central (RC) and in the middle posterior (MP) regions considering only the alpha band

Summary

Introduction

(EEG) signal and variations in carbon dioxide (CO2) signal related to different breathing task. Some models describe the dynamics between CO2 and ventilation using a linear interaction[2,3,4] This assumption does not consider that the respiratory system is a non-linear system[5], especially moving away from the steady state, as in oscillatory phenomena, such as periodic breathing or central/obstructive apneas. Hypercapnia reduces spontaneous neuronal oscillatory power in anaesthetized primate[22] and rats with intracortical electrodes[23] and, if prolonged (8 weeks), causes hypnotic effects without changing the morphological aspect of the brain in rabbits[24] In humans, it is responsible for increasing the δ band (1–4 Hz) EEG power as well as for decreasing the power in the α (8–13 Hz) band[25,26], suggesting that during hypercapnic inhalation, brain activity resembles low arousal state. It has been observed a reduction in EEG power in α- and in β-, and γ-frequency bands[22,27]

Methods

Results

Conclusion