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. 2025 Jan-Dec:29:23312165241311721.
doi: 10.1177/23312165241311721.

Measuring Speech Discrimination Ability in Sleeping Infants Using fNIRS-A Proof of Principle

Onn Wah Lee  1   2   3 , Demi Gao  1   2 , Tommy Peng  1   2 , Julia Wunderlich  1   2 , Darren Mao  1   2 , Gautam Balasubramanian  1   2 , Colette M McKay  1   2
Affiliations

Measuring Speech Discrimination Ability in Sleeping Infants Using fNIRS-A Proof of Principle

Onn Wah Lee et al. Trends Hear. 2025 Jan-Dec.

Abstract

This study used functional near-infrared spectroscopy (fNIRS) to measure aspects of the speech discrimination ability of sleeping infants. We examined the morphology of the fNIRS response to three different speech contrasts, namely "Tea/Ba," "Bee/Ba," and "Ga/Ba." Sixteen infants aged between 3 and 13 months old were included in this study and their fNIRS data were recorded during natural sleep. The stimuli were presented using a nonsilence baseline paradigm, where repeated standard stimuli were presented between the novel stimuli blocks without any silence periods. The morphology of fNIRS responses varied between speech contrasts. The data were fit with a model in which the responses were the sum of two independent and concurrent response mechanisms that were derived from previously published fNIRS detection responses. These independent components were an oxyhemoglobin (HbO)-positive early-latency response and an HbO-negative late latency response, hypothesized to be related to an auditory canonical response and a brain arousal response, respectively. The goodness of fit of the model with the data was high with median goodness of fit of 81%. The data showed that both response components had later latency when the left ear was the test ear (p < .05) compared to the right ear and that the negative component, due to brain arousal, was smallest for the most subtle contrast, "Ga/Ba" (p = .003).

Keywords: arousal; fNIRS; infant; sleep; speech discrimination.

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Conflict of interest statement

Declaration of Conflicting InterestsThe authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: A patent application has been submitted related to the contents of this paper (IP Australia 2022901011). The authors may obtain financial benefit from future use of that patent in a commercial device.

Figures

Figure 1.
Figure 1.
Optode montage. (A) The hemispheric-symmetrical arrangement of optodes used in an International 10-10 System. The sources are positioned over F3/4, FC5/6, CP5/6, and T7/8, whereas the detectors are positioned over FC3/4, F5/6, C5/6 and TP7/8. Red circle = source, blue circle = detector and yellow line = channels. The black circles enclose the four defined regions of interest: left and right temporal and prefrontal regions. (B) The sensitivity profile of our fNIRS measurements on the left hemisphere of the brain.
Figure 2.
Figure 2.
Schematic of the stimulus protocol. The procedure started with 5 min of nonsilence baseline (repeating “Ba” stimulus), followed by novel stimulus blocks where the contrast speech sound was alternated with “Ba.” The nonsilence baseline continued between novel blocks. A total of 20 trials of each of the three contrasts were presented.
Figure 3.
Figure 3.
The two HbO response components (arbitrary amplitude) derived via independent component analysis from detection data of Lee et al. (2024). These templates were used in the current study with limited ranges of amplitude and latency as fitting parameters.
Figure 4.
Figure 4.
HbO (solid red lines) and HbR (solid blue lines) waveforms, averaged across epochs, channels in each ROI and across subjects. The left and right columns are results from infants with left and right ear stimulation, respectively and rows are results for the three different speech contrasts. The dashed red lines are model fits to the HbO data. LPF, RPF signify left and right prefrontal ROIs respectively, and LT, RT signify left and right temporal ROIs respectively.
See this image and copyright information in PMC

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