Measurements of cerebral and muscle oxygenation (StO2) and perfusion ([tHb]) with functional near-infrared spectroscopy (fNIRS) and near infrared spectroscopy (NIRS), respectively, can be influenced by changes in systemic physiology. The aim of our study was to apply the oblique subspace projections signal decomposition (OSPSD) to find the contribution from systemic physiology, i.e. heart rate (HR), electrocardiography (ECG)-derived respiration (EDR) and partial pressure of carbon dioxide (pCO2) to StO2 and [tHb] signals measured on the prefrontal cortex (PFC) and calf muscle. OSPSD was applied to two datasets (n1 = 42, n2 = 79 measurements) from two fNIRS/NIRS speech studies. We found that (i) all StO2 and [tHb] signals contained components related to changes in systemic physiology, (ii) the contribution from systemic physiology varied strongly between subjects, and (iii) changes in systemic physiology generally influenced fNIRS signals on the left and right PFC to a similar degree.
This is a preview of subscription content, log in to check access.
Tachtsidis I, Scholkmann F (2016) False positives and false negatives in functional near-infrared spectroscopy: issues, challenges, and the way forward. Neurophotonics 3(3):031405CrossRefGoogle Scholar
Scholkmann F, Kleiser S, Metz AJ et al (2014) A review on continuous wave functional near-infrared spectroscopy and imaging instrumentation and methodology. NeuroImage 1:6–27CrossRefGoogle Scholar
Scholkmann F, Gerber U, Wolf M et al (2013) End-tidal CO2: an important parameter for a correct interpretation in functional brain studies using speech tasks. NeuroImage 66:71–79CrossRefGoogle Scholar
Scholkmann F, Klein S, Gerber U et al (2014) Cerebral hemodynamic and oxygenation changes induced by inner and heard speech: a study combining functional near-infrared spectroscopy and capnography. J Biomed Opt 19(1):17002CrossRefGoogle Scholar
Wolf U, Scholkmann F, Rosenberger R et al (2011) Changes in hemodynamics and tissue oxygenation saturation in the brain and skeletal muscle induced by speech therapy – A near-infrared spectroscopy study. Sci World J 11:1206–1215CrossRefGoogle Scholar
Scholkmann F, Wolf M, Wolf U (2013) The effect of inner speech on arterial CO2 and cerebral hemodynamics and oxygenation: a functional NIRS study. Adv Exp Med Biol 789:81–87CrossRefGoogle Scholar
Caicedo A, Varon C, Hunadi B et al (2016) Decomposition of near-infrared spectroscopy signals using oblique subspace projections: applications in brain hemodynamic monitoring. Front Physiol 7:515CrossRefGoogle Scholar