The cost and benefit of auditory cortex plasticity during development

A general theory of development holds that a heightened period of neural plasticity underlies both a greater capacity for learning and a greater vulnerability to sensory deprivation, such as hearing loss. To explore the neural mechanisms associated with developmental skill learning, we recorded telemetrically from auditory cortex neurons as freely moving adult and adolescent gerbils attended to, and trained on, an auditory task. Adolescents learned more slowly than adults, consistent with human studies, and auditory cortex neuron sensitivity to the acoustic stimuli displayed smaller improvements during training. Poorer psychometric performance was also observed in adults reared with developmental hearing loss. Again, this was correlated with degraded auditory cortex neuron sensitivity during task performance. Finally, we asked whether degraded perception could be attributed to intrinsic cellular deficits in auditory cortex. Here, we found that hearing loss well before adolescence induced both perceptual deficits and a long-lasting reduction of auditory cortex synaptic inhibition. Furthermore, rescuing synaptic inhibition with a pharmacological treatment, either during or after the period of hearing loss, could restore normal perceptual skills. Together, these findings illustrate age-dependent forms of cortical plasticity that influence both auditory perception and learning.