Acoustic Enrichment Prevents Early Life Stress-Induced Disruptions in Sound Azimuth Processing

Early life stress (ELS) has been shown to disrupt cognitive and limbic functions, yet its impact on sensory systems, particularly the auditory system, remains insufficiently understood. In this study, we investigated the enduring effects of ELS induced by neonatal maternal separation (MS) on behavioral and cortical processing of sound azimuth in adult male rats. We found that MS significantly impairs sound-azimuth discrimination, paralleled by broader azimuth tuning and reduced dendritic branching and spine density in neurons within the primary auditory cortex. Notably, exposure to an enriched acoustic environment during the stress period effectively protects against these MS-induced alterations, restoring behavioral performance, cortical tuning, and dendritic spine density of neurons to levels comparable with controls. Further analyses reveal that epigenetic regulation of cortical brain-derived neurotrophic factor by histone H3 lysine 9 dimethylation may underlie the observed changes in cortical structure and function. These results underscore the profound and lasting impact of MS-induced ELS on auditory processing, particularly within cortical circuits involved in spatial processing. They suggest that sensory enrichment is a potential therapeutic strategy to ameliorate the adverse effects of ELS on sensory processing, with broader implications for understanding and treating sensory deficits in stress-related disorders.