title: Functional magnetic resonance imaging suggests automatization of the cortical response to inspiratory threshold loading in humans.
abstract: Inspiratory threshold loading (ITL) induces cortical activation. It is sustained over time and is resistant to distraction, suggesting automaticity. We hypothesized that ITL-induced changes in cerebral activation may differ between single-breath ITL and continuous ITL, with differences resembling those observed after cortical automatization of motor tasks. We analyzed the brain blood oxygen level dependent (BOLD) signal of 11 naive healthy volunteers during 5 min of random, single-breath ITL and 5 min of continuous ITL. Single-breath ITL increased BOLD in many areas (premotor cortices, bilateral insula, cerebellum, reticular formation of the lateral mesencephalon) and decreased BOLD in regions co-localizing with the default mode network. Continuous ITL induced signal changes in a limited number of areas (supplementary motor area). These differences are comparable to those observed before and after overlearning of motor tasks. We conclude that the respiratory-related cortical activation observed in response to ITL is likely due to automated, attention-independent mechanisms. Also, ITL activates cortical circuits right from the first breath.
authors.affiliation: Department of Experimental Medicine, Transcranial Magnetic Stimulation Laboratory McGill University Health Centre, Montréal, QC, Canada; Université Paris 6, ER10UPMC Neurophysiologie Respiratoire Expérimentale et Clinique, Paris, France; Assistance Publique - Hôpitaux de Paris, Département d'Anesthésie Réanimation, Groupe Hospitalier Pitié-Salpêtrière, Paris, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Raux
authors.forename: Louise
authors.initials: L
authors.lastname: Tyvaert
authors.forename: Michael
authors.initials: M
authors.lastname: Ferreira
authors.forename: Félix
authors.initials: F
authors.lastname: Kindler
authors.forename: Eric
authors.initials: E
authors.lastname: Bardinet
authors.forename: Carine
authors.initials: C
authors.lastname: Karachi
authors.forename: Capucine
authors.initials: C
authors.lastname: Morelot-Panzini
authors.forename: Jean
authors.initials: J
authors.lastname: Gotman
authors.forename: G Bruce
authors.initials: GB
authors.lastname: Pike
authors.forename: Lisa
authors.initials: L
authors.lastname: Koski
authors.forename: Thomas
authors.initials: T
authors.lastname: Similowski
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000098:blood supply*; D004056:Differential Threshold / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D001239:Inhalation / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D005082:Physical Exertion / Q000502:physiology*; D012121:Respiration, Artificial; D013990:Tidal Volume / Q000502:physiology; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: Cerebral cortex; Control of breathing; Dyspnea; Inspiratory loading