Prenatal exposure to antidepressants and depressed maternal mood alter trajectory of infant speech perception

Abstract

Language acquisition reflects a complex interplay between biology and early experience. Psychotropic medication exposure has been shown to alter neural plasticity and shift sensitive periods in perceptual development. Notably, serotonin reuptake inhibitors (SRIs) are antidepressant agents increasingly prescribed to manage antenatal mood disorders, and depressed maternal mood per se during pregnancy impacts infant behavior, also raising concerns about long-term consequences following such developmental exposure. We studied whether infants' language development is altered by prenatal exposure to SRIs and whether such effects differ from exposure to maternal mood disturbances. Infants from non-SRI-treated mothers with little or no depression (control), depressed but non-SRI-treated (depressed-only), and depressed and treated with an SRI (SRI-exposed) were studied at 36 wk gestation (while still in utero) on a consonant and vowel discrimination task and at 6 and 10 mo of age on a nonnative speech and visual language discrimination task. Whereas the control infants responded as expected (success at 6 mo and failure at 10 mo) the SRI-exposed infants failed to discriminate the language differences at either age and the depressed-only infants succeeded at 10 mo instead of 6 mo. Fetuses at 36 wk gestation in the control condition performed as expected, with a response on vowel but not consonant discrimination, whereas the SRI-exposed fetuses showed accelerated perceptual development by discriminating both vowels and consonants. Thus, prenatal depressed maternal mood and SRI exposure were found to shift developmental milestones bidirectionally on infant speech perception tasks.L anguage, our most quintessential human characteristic, involves a complex interplay between biology and experience. At birth, infants possess an initial preparedness for language and a developmental readiness that supports learning any of the world's languages (1-3), yet also already show privileged processing to the native language from prenatal listening experience (4-6). During the following weeks and months of life, infants become progressively attuned to the properties of their native language, including its rhythmical and segmental (e.g., consonant) information (reviewed in refs. 7 and 8). The high degree of regularity in the timing of sequential tuning to properties of the native language suggests a series of critical or sensitive periods, i.e., points in development when the system is maximally influenced by input.The timing of onset of these sensitive periods seems to be maturationally constrained. Infants born 3 mo preterm attune to the phonetic properties (9) of their native language at the same gestational age as full-term infants, not according to the number of months of postnatal listening experience. Such maturational constraints can protect development: ensuring the optimal consecutive stabilization of the perceptual components that contribute in a step-wise fashion to language acquisition (10). However, it is known from research i...

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