title: Speech-evoked activation in adult temporal cortex measured using functional near-infrared spectroscopy (fNIRS): Are the measurements reliable?
abstract: Functional near-infrared spectroscopy (fNIRS) is a silent, non-invasive neuroimaging technique that is potentially well suited to auditory research. However, the reliability of auditory-evoked activation measured using fNIRS is largely unknown. The present study investigated the test-retest reliability of speech-evoked fNIRS responses in normally-hearing adults. Seventeen participants underwent fNIRS imaging in two sessions separated by three months. In a block design, participants were presented with auditory speech, visual speech (silent speechreading), and audiovisual speech conditions. Optode arrays were placed bilaterally over the temporal lobes, targeting auditory brain regions. A range of established metrics was used to quantify the reproducibility of cortical activation patterns, as well as the amplitude and time course of the haemodynamic response within predefined regions of interest. The use of a signal processing algorithm designed to reduce the influence of systemic physiological signals was found to be crucial to achieving reliable detection of significant activation at the group level. For auditory speech (with or without visual cues), reliability was good to excellent at the group level, but highly variable among individuals. Temporal-lobe activation in response to visual speech was less reliable, especially in the right hemisphere. Consistent with previous reports, fNIRS reliability was improved by averaging across a small number of channels overlying a cortical region of interest. Overall, the present results confirm that fNIRS can measure speech-evoked auditory responses in adults that are highly reliable at the group level, and indicate that signal processing to reduce physiological noise may substantially improve the reliability of fNIRS measurements.
authors.affiliation: National Institute for Health Research (NIHR) Nottingham Hearing Biomedical Research Unit, 113 The Ropewalk, Nottingham, NG1 5DU, United Kingdom; Otology and Hearing Group, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, Nottingham, NG7 2UH, United Kingdom; Medical Research Council (MRC) Institute of Hearing Research, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom. Electronic address: ian.wiggins@nottingham.ac.uk.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Wiggins
authors.affiliation: National Institute for Health Research (NIHR) Nottingham Hearing Biomedical Research Unit, 113 The Ropewalk, Nottingham, NG1 5DU, United Kingdom; Otology and Hearing Group, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, Nottingham, NG7 2UH, United Kingdom.
authors.forename: Carly A
authors.initials: CA
authors.lastname: Anderson
authors.affiliation: National Institute for Health Research (NIHR) Nottingham Hearing Biomedical Research Unit, 113 The Ropewalk, Nottingham, NG1 5DU, United Kingdom; Otology and Hearing Group, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, Nottingham, NG7 2UH, United Kingdom.
authors.forename: Pádraig T
authors.initials: PT
authors.lastname: Kitterick
authors.affiliation: National Institute for Health Research (NIHR) Nottingham Hearing Biomedical Research Unit, 113 The Ropewalk, Nottingham, NG1 5DU, United Kingdom; Otology and Hearing Group, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, Nottingham, NG7 2UH, United Kingdom; Medical Research Council (MRC) Institute of Hearing Research, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom; Nottingham University Hospitals NHS Trust, Derby Road, Nottingham, NG7 2UH, United Kingdom.
authors.forename: Douglas E H
authors.initials: DE
authors.lastname: Hartley
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000368:Aged; D000465:Algorithms; D001303:Auditory Cortex / Q000502:physiology*; D001921:Brain / Q000502:physiology; D001931:Brain Mapping / Q000379:methods*; D005072:Evoked Potentials, Auditory; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D019265:Spectroscopy, Near-Infrared; D013060:Speech; D013702:Temporal Lobe / Q000502:physiology*
keywords: Auditory cortex; Functional near-infrared spectroscopy; Speech; Speechreading; Test-retest reliability; fNIRS