Abstract
The current study characterized subcortical speech sound processing among monolinguals and bilinguals in quiet and challenging listening conditions and examined the relation between subcortical neural processing and perceptual performance. A total of 59 normal-hearing adults, ages 19–35 years, participated in the study: 29 native Hebrew-speaking monolinguals and 30 Arabic-Hebrew-speaking bilinguals. Auditory brainstem responses to speech sounds were collected in a quiet condition and with background noise. The perception of words and sentences in quiet and background noise conditions was also examined to assess perceptual performance and to evaluate the perceptual-physiological relationship. Perceptual performance was tested among bilinguals in both languages (first language (L1-Arabic) and second language (L2-Hebrew)). The outcomes were similar between monolingual and bilingual groups in quiet. Noise, as expected, resulted in deterioration in perceptual and neural responses, which was reflected in lower accuracy in perceptual tasks compared to quiet, and in more prolonged latencies and diminished neural responses. However, a mixed picture was observed among bilinguals in perceptual and physiological outcomes in noise. In the perceptual measures, bilinguals were significantly less accurate than their monolingual counterparts. However, in neural responses, bilinguals demonstrated earlier peak latencies compared to monolinguals. Our results also showed that perceptual performance in noise was related to subcortical resilience to the disruption caused by background noise. Specifically, in noise, increased brainstem resistance (i.e., fewer changes in the fundamental frequency (F0) representations or fewer shifts in the neural timing) was related to better speech perception among bilinguals. Better perception in L1 in noise was correlated with fewer changes in F0 representations, and more accurate perception in L2 was related to minor shifts in auditory neural timing. This study delves into the importance of using neural brainstem responses to speech sounds to differentiate individuals with different language histories and to explain inter-subject variability in bilinguals’ perceptual abilities in daily life situations.
Highlights
Interactions frequently occur in acoustically challenging environments, which often pose challenges to listeners
The current study characterized the subcortical neural processing of speech sounds and the perceptual performance of normal-hearing bilinguals and monolinguals in quiet and noisy conditions. We examined how this subcortical neural processing is related to perceptual performance
Our results demonstrated that the effect of lifelong experience with two languages–bilingualism–was reflected mainly in perceptual and neural measures in challenging listening conditions
Summary
Interactions frequently occur in acoustically challenging environments, which often pose challenges to listeners. One challenging listening condition that deteriorates speech perception is background noise [1,2,3] It is well-known that speech perception in the presence of background noise can be more challenging for bilinguals compared to monolinguals [4,5,6,7,8,9,10,11,12,13,14,15,16] and that this disadvantage is present even when bilinguals have early exposure and strong proficiency in both languages [7, 16, 17]. The puzzling question of how the perceptual disadvantage of bilinguals aligns with the advantage seen in subcortical processes remains. In an attempt to answer this question, the current study examined the association between perceptual and physiological outcomes
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