title: Time-frequency dynamics of the sum of intra- and extracerebral hemodynamic functional connectivity during resting-state and respiratory challenges assessed by multimodal functional near-infrared spectroscopy.
abstract: Monitoring respiratory processes is important for evaluating neuroimaging data, given their influence on time-frequency dynamics of intra- and extracerebral hemodynamics. Here we investigated the time-frequency dynamics of the sum of intra- and extracerebral hemodynamic functional connectivity states during hypo- and hypercapnia by using three different respiratory challenge tasks (i.e., hyperventilation, breath-holding, and rebreathing) compared to resting-state. The sum of intra- and extracerebral hemodynamic responses were assessed using functional near-infrared spectroscopy (fNIRS) within two regions of interest (i.e., the dorsolateral and the medial prefrontal cortex). Time-frequency fNIRS analysis was performed based on wavelet transform coherence to quantify functional connectivity in terms of positive and negative phase-coupling within each region of interest. Physiological measures were assessed in the form of partial end-tidal carbon dioxide, heart rate, arterial tissue oxygen saturation, and respiration rate. We found that the three respiration challenges modulated time-frequency dynamics differently with respect to resting-state: 1) Hyperventilation and breath-holding exhibited inverse patterns of positive and negative phase-coupling. 2) In contrast, rebreathing had no significant effect. 3) Low-frequency oscillations contributed to a greater extent to time-frequency dynamics compared to high-frequency oscillations. The results highlight that there exist distinct differences in time-frequency dynamics of the sum of intra- and extracerebral functional connectivity not only between hypo- (hyperventilation) and hypercapnia but also between different states of hypercapnia (breath-holding versus rebreathing). This suggests that a multimodal assessment of intra-/extracerebral and systemic physiological changes during respiratory challenges compared to resting-state may have potential use in the differentiation between physiological and pathological respiratory behavior accompanied by the psycho-physiological state of a human.
authors.affiliation: Department of Psychiatry, Psychotherapy, and Psychosomatics, University Hospital of Psychiatry Zurich, Lenggstrasse 31, 8032 Zurich, Switzerland. Electronic address: lisa.holper@puk.zh.ch.
authors.forename: L
authors.initials: L
authors.lastname: Holper
authors.affiliation: Biomedical Optics Research Laboratory, Division of Neonatology, University Hospital Zurich, University of Zurich, Frauenklinikstrasse 10, 8091 Zurich, Switzerland.
authors.forename: F
authors.initials: F
authors.lastname: Scholkmann
authors.affiliation: Department of Psychiatry, Psychotherapy, and Psychosomatics, University Hospital of Psychiatry Zurich, Lenggstrasse 31, 8032 Zurich, Switzerland.
authors.forename: E
authors.initials: E
authors.lastname: Seifritz
mesh_terms: D000328:Adult; D062485:Breath Holding; D019296:Capnography; D005260:Female; D059907:Functional Neuroimaging; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D006985:Hyperventilation / Q000503:physiopathology*; D016857:Hypocapnia / Q000503:physiopathology; D007040:Hypoventilation / Q000503:physiopathology*; D008297:Male; D000069336:Neurovascular Coupling / Q000502:physiology*; D017397:Prefrontal Cortex / Q000502:physiology* / Q000503:physiopathology; D012119:Respiration; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
keywords: Functional near-infrared spectroscopy; Partial pressure of carbon dioxide; Resting-state; Time–frequency dynamics of intra- and extracortical hemodynamic functional connectivity