Neural speech encoding in fetal alcohol spectrum disorder: an exploratory study using frequency-following responses

Fetal alcohol spectrum disorder (FASD) is associated with neurodevelopmental impairments, including listening difficulties not always explained by peripheral hearing loss, suggesting alterations at the level of neural auditory processing. The frequency-following response (FFR) provides an objective measure of neural speech encoding and may offer insight into auditory function in this population.

Twenty-five normal-hearing participants were included: 11 individuals with FASD and 14 controls. Speech-evoked FFRs were recorded using a 160 ms /da/ stimulus at 80 dB SPL with a stimulation rate of 4.35/s. Pitch tracking, stimulus-response correlation, response latency, and signal quality were analyzed using non-parametric statistics. Given the exploratory nature of the study and uncontrolled demographic variables - including a significant age difference between groups - findings should be interpreted as preliminary and hypothesis-generating.

Compared to controls, individuals with FASD showed reduced pitch-tracking consistency and lower stimulus-response correlation, with the most robust finding being a large-effect reduction in F0-range correlation (R[70-120 Hz]: p < 0.001, rank-biserial r = 0.823). Prolonged latencies were observed across multiple response components, and signal-to-noise ratio tended to be lower in the FASD group.

This exploratory proof-of-concept study provides preliminary evidence of altered neural speech encoding in individuals with FASD despite normal peripheral hearing. Given uncontrolled confounds, observed differences cannot be specifically attributed to FASD. These findings establish the feasibility of FFR in this population and provide the empirical foundation for future controlled research on auditory biomarkers and intervention monitoring in FASD.