Poster A69, Thursday, August 16, 10:15 am – 12:00 pm, Room 2000AB
Neural processing of sound in bilinguals: The influence of early-life dual language exposure on auditory processing in adults
Erika Skoe1;1University of Connecticut
The literature on the neurobiological correlates of bilingualism is vast. Yet, despite this wealth of knowledge, comparatively little is known about how being exposed to multiple spoken languages influences sound processing in the brain. Over the past decade, the frequency-following response (FFR) has emerged as an important electrophysiological tool for studying individual variability in the neural processing of sound associated with language. The FFR, a neuro-electric potential recorded at the scalp, is a phase-locked response to periodic aspects of sound (e.g. vowels, vocal pitch contours) that reflects a composite of multiple generators within the auditory neuroaxis. Recent reports indicate that bilingual children, adolescents, and adults, who learned both languages simultaneously, have more robust neural responses to the fundamental frequency (F0) of vowels, as measured by the FFR. Comparisons of simultaneous vs. sequential bilingual children have further suggested that these neural enhancements track with the total years of bilingual experience. However, an alternative interpretation is that these group differences are reflective of differential patterns of auditory exposure during sensitive periods in the development of the auditory neuroaxis. The FFR undergoes considerable developmental changes: the amplitude of the FFR to the F0 increases sharply in early childhood, reaching its maximum between ages 5-8, after which the amplitude declines progressively. Studies of FFRs from musicians have suggested that experience-dependent plasticity is amplified and longer lasting when it coincides with periods of significant developmental change. If early-life auditory experiences are indeed critical for shaping later-life auditory function, this leads to the prediction that the magnitude of the FFR enhancement should relate to individual differences in language exposure early in life, with current language exposure making less of a contribution. To test this possibility, FFRs to synthesized speech sounds were recorded in young adults (n=23, 18-24 years), who learned English in conjunction with another language before the age of 4 years. At the time of testing, all participants self-rated their English proficiency at the native-level. Participants ranged in terms of their current proficiency in the non-English language (NEL), with ratings spanning from 4-10 (10 = native level of fluency). They also ranged in terms of their current daily exposure to NEL (0-50%), and their early life (0-3 years of age) NEL exposure (5-100%). In this data sample, there was also a strong association between the amount of NEL exposure during the 0-3 age window and the amount of decay in NEL exposure from infancy to current age. Consistent with predictions, the magnitude of the neural response to F0 correlated with participants’ earliest language exposure to NEL but not their current language exposure. Specifically, participants with greater exposure to NEL during the first three years of their life had stronger neural responses to sound than those reporting less early life exposure to NEL. These findings add to the evidence that dual-language experience influences the neural processing of sound, and they provide new insight into the underlying mechanisms, and experiential factors, that contribute to auditory plasticity associated with bilingualism.
Topic Area: Multilingualism