Seminars in Hearing Research

Date: Thursday, March 27, 2025

Location: Nelson 1215

Time: Noon - 1:00 pm

Speaker: Abigail Anne Mollison PhD Student, SLHS 

Title: Analyzing group auditory test-retest reliability through systemic physiology augmented fNIRS

Abstract:  Functional near-infrared spectroscopy (fNIRS) is a neuroimaging technique that is both affordable and accessible, making it a valuable tool for measuring cortical activation in clinical populations. However, fNIRS data captures both cortical activity and systemic physiological processes, resulting in “noise” that reduces fNIRS signal quality. Such noise can compromise the reliability of group-level data, potentially leading to false positives in cortical activity. Additionally, fNIRS cap placement may vary across individuals and across sessions, possibly leading to additional measurement noise caused by changes in optode location. The aim of this study was to assess the test-retest reliability of group-level fNIRS data reflecting cortical activity associated with speech listening across multiple sessions. Participants completed two sessions of a passive-listening task followed by a 3D head scan used to digitize and track optode placement across sessions. Different denoising methods that corrected for both extracerebral and full-body systemic physiology were compared based on degree of systemic noise removal for each session. Test-retest reliability across sessions was measured using the intraclass correlation coefficient (ICC). Changes in within subject optode scalp location was measured by calculating the Euclidean distance between sessions. During passive speech-listening conditions, we observed significant activity in the auditory cortices following stimuli presentation. At the group-level, hemodynamic responses elicited by speech stimuli were more reliable compared to silent conditions. However, implementing denoising methods that accounted for more systemic noise reduced test-retest reliability. The presence of systemic noise can erroneously reinforce cortical activation patterns; more intensive denoising methods likely reduce reliability because the presence of systemic noise in fNIRS data can artificially inflate reliability metrics. Slight variations in optode placement across sessions did not significantly affect signal repeatability, as channel movement remained within specified regions of interest. This study supports the use of fNIRS for reliable group-level task-evoked studies, demonstrating that denoising methods can enhance data accuracy at the group level and that small changes in cap placement do not substantially impact data reliability.

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The working schedule is available here: https://purdue.edu/TPAN/hearing/shrp_schedule

The titles and abstracts of the talks will be added here: https://purdue.edu/TPAN/hearing/shrp_abstracts