Neural mechanisms supporting language acquisition

We, as humans, are biologically predisposed to acquire language. The language journey begins already in the womb, where the fetus is first exposed to melodic and rhythmic features of the native language(s). Even if partial, this early auditory experience coupled with the innate predisposition of the human brain for language establishes the foundations for language acquisition. At birth, newborns show universal perceptual abilities that gradually attune toward the native language. Prenatal experience with speech prosody facilitates the neural tracking of the native language(s) and of those rhythmically similar, while the alteration or the complete absence of this early input can compromise subsequent linguistic acquisitions. When such alterations are further combined with a lack of sufficient postnatal auditory stimulation, as in the case of deaf or hard-of-hearing infants, the potential consequences for language development can be even more pronounced. In this thesis, we explored how congenitally deaf and hard-of-hearing infants process speech prosody. Our findings demonstrate that, depending on hearing loss severity, rhythmic and linguistic discrimination is still preserved, although the underlying neural processing diverges from what is observed in infants with normal hearing. Importantly, correctly amplified hearing residuals have emerged as an essential factor, especially in those infants who are candidates for cochlear implants. This minimal auditory experience seems to importantly support the restoration of more prototypical brain responses after cochlear implantation, as well as the development of better perceptual and language abilities. Additionally, we provided new evidence that the infant brain is neurodevelopmentally prepared to process linguistic input that is particularly relevant to the developmental stage the child is approaching in production, reinforcing the hypothesis of an early and tight link between speech perception and speech production abilities. Taken together, this work, alongside a growing body of research on infant speech perception, speech perception-production abilities and the consequences of auditory deprivation, highlights the impressive preparedness and plasticity of the developing brain, even in response to an altered sensory input and that timely and effective interventions can play a decisive role in optimizing developmental outcomes.