title: Cerebral hemodynamic and oxygenation changes induced by inner and heard speech: a study combining functional near-infrared spectroscopy and capnography.
abstract: The aim of this study was to investigate the effects of inner and heard speech on cerebral hemodynamics and oxygenation in the anterior prefrontal cortex (PFC) using functional near-infrared spectroscopy and to test whether potential effects were caused by alterations in the arterial carbon dioxide pressure (PaCO2). Twenty-nine healthy adult volunteers performed six different tasks of inner and heard speech according to a randomized crossover design. During the tasks, we generally found a decrease in PaCO2 (only for inner speech), tissue oxygen saturation (StO2), oxyhemoglobin ([O2Hb]), total hemoglobin ([tHb]) concentration and an increase in deoxyhemoglobin concentration ([HHb]). Furthermore, we found significant relations between changes in [O2Hb], [HHb], [tHb], or StO2 and the participants' age, the baseline PETCO2, or certain speech tasks. We conclude that changes in breathing during the tasks led to lower PaCO2 (hypocapnia) for inner speech. During heard speech, no significant changes in PaCO2 occurred, but the decreases in StO2, [O2Hb], and [tHb] suggest that changes in PaCO2 were also involved here. Different verse types (hexameter and alliteration) led to different changes in [tHb], implying different brain activations. In conclusion, StO2, [O2Hb], [HHb], and [tHb] are affected by interplay of both PaCO2 reactivity and functional brain activity.
authors.affiliation: University of Bern, Institute of Complementary Medicine IKOM, 3010 Bern, SwitzerlandbUniversity Hospital Zurich, Division of Neonatology, Biomedical Optics Research Laboratory, 8091 Zurich, Switzerland.
authors.forename: Felix
authors.initials: F
authors.lastname: Scholkmann
authors.affiliation: University of Bern, Institute of Complementary Medicine IKOM, 3010 Bern, Switzerland.
authors.forename: Sabine D
authors.initials: SD
authors.lastname: Klein
authors.affiliation: University of Bern, Institute of Complementary Medicine IKOM, 3010 Bern, Switzerland.
authors.forename: Ursina
authors.initials: U
authors.lastname: Gerber
authors.affiliation: University Hospital Zurich, Division of Neonatology, Biomedical Optics Research Laboratory, 8091 Zurich, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Wolf
authors.affiliation: University of Bern, Institute of Complementary Medicine IKOM, 3010 Bern, Switzerland.
authors.forename: Ursula
authors.initials: U
authors.lastname: Wolf
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology; D001931:Brain Mapping; D019296:Capnography / Q000379:methods*; D002245:Carbon Dioxide / Q000032:analysis; D018592:Cross-Over Studies; D005260:Female; D006309:Hearing; D006439:Hemodynamics; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009068:Movement; D010100:Oxygen / Q000032:analysis / Q000737:chemistry*; D010108:Oxyhemoglobins / Q000032:analysis; D017397:Prefrontal Cortex / Q000098:blood supply* / Q000473:pathology; D012815:Signal Processing, Computer-Assisted; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013060:Speech; D013997:Time Factors
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins; D002245:Carbon Dioxide; C100003:deoxyhemoglobin; D010100:Oxygen