Localization of Cortical Responses to Audiovisual, Visual, and Auditory Presented Speech Using fNIRS: An Exploratory Study in Normal-Hearing Adults

Background: Functional near-infrared spectroscopy (fNIRS) is a promising non-invasive functional imaging technique that is compatible with hearing devices. However, fNIRS is only recently adopted in auditory research, and considerable variability exists in the experimental designs and analysis techniques used. Hence, the current study aimed to set up and test an fNIRS protocol to localize cortical activation to audiovisual, visual, and auditory speech in normal-hearing adults. Methods: A group of 31 normal-hearing adults was included. A semi-random block design was applied, using speech samples of bi-syllabic Dutch words as stimuli, randomly alternating between auditory, visual, and audio-visual presentations. Besides, a silent control condition was included. Optodes were placed bilaterally on the auditory and visual cortices. Data were analyzed using MNE-Python. Cortical activation pat terns per condition were determined. Results: Results showed that cortical activity was localized in the left temporal cortex during auditory speech stimulation. However, this activation was not significantly different from baseline. During visual speech stimulation, significant activation was found in the occipital cortex. This region also showed significant activation during audiovisual speech stimulation, in addition to non-significant activity in the left temporal cortex. Conclusion: The current study provides evidence that fNIRS can be a useful neuroimaging technique in auditory research, especially for mea suring cortical activation patterns during auditory, visual, and audiovisual speech stimuli. Future work will compare the current results obtained in normal-hearing individuals to the activation patterns of cochlear implant users and hearing aid users. Cite this article as: Ceuleers D, Eqlimi E, Swinnen F, Hannah H, Dhooge I. Localization of cortical responses to audiovisual, visual, and auditory presented speech using fNIRS: An exploratory study in normal-hearing adults. B-ENT. 2025;21(1):31-38.