Environmental enrichment improves behavioral performance and auditory spatial representation of primary auditory cortical neurons in rat

Environmental enrichment (EE) has an important role in brain plasticity. Early research has shown that EE increases the response strength of neurons in the auditory cortex, but it remains unknown whether EE can influence the process of spatial localization in the auditory system. In this study, we raised rats in enriched and standard conditions from postnatal day 10 to day 56. By testing behavioral tasks via auditory cues. we have shown that EE improved the number of correct scores, but decreased the reaction time and azimuth deviation in behavioral performance of sound-azimuth discrimination. By in vivo extracellular recording, we have shown that EE enhanced the directional sensitivity of neurons in the primary auditory cortex. For example, EE rats had a smaller spatial receptive field, sharper frequency tuning curve and directional selective curve of auditory neurons compared with normal rats. Our findings indicate that early exposure to EE increases directional sensitivity. These results provide an insight into developmental plasticity in the auditory system. (C) 2009 Elsevier Inc. All rights reserved.