Developmental Trajectory of Auditory Brainstem Deficits in a Mouse Model of Fetal Alcohol Spectrum Disorders

Individuals with fetal alcohol spectrum disorders exhibit impaired auditory processing and atypical auditory behaviors across the disorder's spectrum. Although low to moderate prenatal alcohol exposure (PAE) is a prevalent type of exposure, the developmental trajectory of auditory processing deficits resulting from this level of exposure remains unknown. To examine the effects of PAE in the auditory system, we utilized the maternal voluntary alcohol consumption paradigm to model chronic low to moderate PAE throughout gestation. We measured auditory brainstem responses (ABRs) in juvenile mice (postnatal day 16-19) and longitudinally across early adolescence (4-5 weeks), late adolescence (7-8 weeks), and young adulthood (12-14 weeks). ABR abnormalities were first observed in juvenile PAE mice. The effects of PAE on brainstem auditory processing were most prominent in early adolescence, largely dissipated in late adolescence, and showed a reemergence in early adulthood. PAE mice showed elevated ABR thresholds, prolonged wave latencies, and reduced wave amplitudes. Ratios of ABR peak 3 relative to the first ABR peak indicated that the auditory brainstem pathways were hyperactive in PAE mice. The amplitude ratio was found to be elevated from early adolescence to early adulthood, suggesting that PAE has a persistent effect on auditory processing. We found a significant correlation between the amplitude ratios in early adolescent PAE mice and dam ethanol consumption, which point toward dose-dependent brainstem gain dysregulation. Our study shows multilevel auditory alterations highlighting the vulnerability of central auditory pathways to PAE and fills an important gap in understanding auditory processing deficits in a clinically relevant exposure model.