title: Modelling confounding effects from extracerebral contamination and systemic factors on functional near-infrared spectroscopy.
abstract: Haemodynamics-based neuroimaging is widely used to study brain function. Regional blood flow changes characteristic of neurovascular coupling provide an important marker of neuronal activation. However, changes in systemic physiological parameters such as blood pressure and concentration of CO2can also affect regional blood flow and may confound haemodynamics-based neuroimaging. Measurements with functional near-infrared spectroscopy (fNIRS) may additionally be confounded by blood flow and oxygenation changes in extracerebral tissue layers. Here we investigate these confounds using an extended version of an existing computational model of cerebral physiology, 'BrainSignals'. Our results show that confounding from systemic physiological factors is able to produce misleading haemodynamic responses in both positive and negative directions. By applying the model to data from previous fNIRS studies, we demonstrate that such potentially deceptive responses can indeed occur in at least some experimental scenarios. It is therefore important to record the major potential confounders in the course of fNIRS experiments. Our model may then allow the observed behaviour to be attributed among the potential causes and hence reduce identification errors.
authors: University College London, Department of Medical Physics and Biomedical Engineering, Biomedical Optics Research Laboratory, Gower Street, London WC1E 6BT, United Kingdom.
authors: Matthew
authors: M
authors: Caldwell
authors: University Hospital Zurich, Department of Neonatology, Biomedical Optics Research Laboratory, 8091 Zurich, Switzerland.
authors: Felix
authors: F
authors: Scholkmann
authors: University of Bern, Institute of Complementary Medicine, 3012 Bern, Switzerland.
authors: Ursula
authors: U
authors: Wolf
authors: University Hospital Zurich, Department of Neonatology, Biomedical Optics Research Laboratory, 8091 Zurich, Switzerland.
authors: Martin
authors: M
authors: Wolf
authors: University College London, Department of Medical Physics and Biomedical Engineering, Biomedical Optics Research Laboratory, Gower Street, London WC1E 6BT, United Kingdom.
authors: Clare
authors: C
authors: Elwell
authors: University College London, Department of Medical Physics and Biomedical Engineering, Biomedical Optics Research Laboratory, Gower Street, London WC1E 6BT, United Kingdom. Electronic address: i.tachtsidis@ucl.ac.uk.
authors: Ilias
authors: I
authors: Tachtsidis
mesh_terms: D000328:Adult; D002560:Cerebrovascular Circulation / Q000502:physiology*; D059907:Functional Neuroimaging / Q000379:methods* / Q000592:standards; D006801:Humans; D008962:Models, Theoretical; D019265:Spectroscopy, Near-Infrared / Q000379:methods* / Q000592:standards
keywords: Brain; CO2 reactivity; Confounding; Functional near-infrared spectroscopy; Modelling; Scalp