Abstract
We evaluated whether blind subjects have advantages in auditory spectral resolution, temporal resolution, and speech perception in noise compared with sighted subjects. We also compared psychoacoustic performance between early blind (EB) subjects and late blind (LB) subjects. Nineteen EB subjects, 16 LB subjects, and 20 sighted individuals were enrolled. All subjects were right-handed with normal and symmetric hearing thresholds and without cognitive impairments. Three psychoacoustic measurements of the subjects’ right ears were performed via an inserted earphone to determine spectral-ripple discrimination (SRD), temporal modulation detection (TMD), and speech recognition threshold (SRT) in noisy conditions. Acoustic change complex (ACC) responses were recorded during passive listening to standard ripple-inverted ripple stimuli. EB subjects exhibited better SRD than did LB (p = 0.020) and sighted (p = 0.003) subjects. TMD was better in EB (p < 0.001) and LB (p = 0.007) subjects compared with sighted subjects. SRD was positively correlated with the duration of blindness (r = 0.386, p = 0.024). Acoustic change complex data for ripple noise change at the Cz and Fz electrodes showed trends toward significant correlations with the behavioral results. In conclusion, compared with sighted subjects, EB subjects showed advantages in terms of auditory spectral and temporal resolution, while LB subjects showed an advantage in temporal resolution exclusively. These findings suggest that it might take longer for auditory spectral resolution to functionally enhance following visual deprivation compared to temporal resolution. Alternatively, a critical period of very young age may be required for auditory spectral resolution to improve following visual deprivation.
Highlights
Humans commonly perceive surrounding information via sensory convergence
The Bonferroni post hoc test revealed that temporal modulation detection (TMD) was better in early blind (EB) and late blind (LB) subjects than in sighted subjects (p < 0.001 and p = 0.035, respectively; Figure 2B)
In the 35 EB and LB subjects, spectral-ripple discrimination (SRD) thresholds were significantly correlated with the duration of blindness (r = 0.386, p = 0.024; Figure 3A), whereas TMD thresholds and speech recognition threshold (SRT) were not correlated with duration of blindness (r = −0.298, p = 0.082 and r = −0.104, p = 0.552)
Summary
Humans commonly perceive surrounding information via sensory convergence. The integration of multiple senses can reduce perceptual ambiguity, speed up reactions, and increase the accuracy of stimulus detection. Few studies have compared speech perception without visual cues between blind and sighted subjects, and the results varied considerably (Muchnik et al, 1991; Hugdahl et al, 2004; Gougoux et al, 2009; Arnaud et al, 2018). It has been reported that compared with sighted subjects, blind subjects show better spectral and temporal resolutions, as measured by pitch discrimination or pure-tone discrimination (Gougoux et al, 2004; Rokem and Ahissar, 2009; Wan et al, 2010; Voss and Zatorre, 2012) and an auditory backward temporal masking task (Stevens and Weaver, 2005), the acoustic stimuli used in these previous studies were often band-limited and, may not reflect the temporal and spectral resolution of hearing for broad-band stimuli such as speech signals. In the current study, we used a broad-band noise carrier that is either spectrally modulated (i.e., rippled spectra noise to evaluate spectral envelope sensitivity) or temporally modulated (i.e., temporally modulated noise to evaluate amplitude envelope sensitivity)
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