Environmental enrichment rescues the degraded auditory temporal resolution of cortical neurons induced by early noise exposure.

Abstract

The accurate processing of sound temporal information is crucial to human speech perception and other species-specific communication. During postnatal development, the auditory cortex shows environmental and experience-dependent plasticity. However, how the postnatal environment affects cortical processing of sound temporal information is not fully understood. The aim of the present study was to determine whether postnatal noise exposure impairs neural temporal resolution in the auditory cortex, and, if so, whether environmental enrichment can rescue this degraded neural temporal acuity. Using the neural gap detection threshold determined in anesthetized rats as an index of temporal acuity, we found that exposure of juvenile rats to moderate-level noise induced much higher neural gap detection thresholds in adulthood than exposure of adult rats to the same noise. Environmental enrichment did not affect cortical neural gap detection thresholds in normally developing rats. However, rearing of rats with early noise exposure in an enriched environment promoted recovery from the noise-induced degraded neural temporal resolution. In addition, the tonal stimuli in the enriched environment contributed to only a portion of the recovery. These results provide evidence for noise-induced developmental impairment in neural gap detection thresholds in the auditory cortex, and suggest a therapeutic potential for environmental enrichment as a non-invasive approach to rescue developmentally degraded auditory temporal processing.