Environment Enrichment Reverses Defects In Learning And Memory Of ASD Rats Induced By VPA

It has been shown that the environment enrichment can enhance structural and functional plasticity in the brain,thereby improving learning and memory processing.In this dissertation,we aim to study the reversal effects of the environment enrichment on deficits in learning and memory in Valproic Acid(VPA)-induced autism rat models.VPA animals were exposed to an enriched environment for 50 days.The acoustic frequency discrimination task,T-maze,and Y-maze were then used to examine behavioral changes in learning and memory in these model rats.The results showed that abilities to discriminate the sound frequencies,the percent correct in the T-maze test,and the time spent in the novel arm of the Y-maze for VPA animals were all decreased significantly than those of the normal animals.All above behavioral performances,however,have various degrees of improvement in VPA animals after the processing of the environment enrichment.Due to the important roles of Parvalbumin(PV)and Somatostatin(SOM)inhibitory inter-neurons in learning and memory processing,we further investigated the changes of the distribution density of these two types of inter-neurons in the hippocampus and medial prefrontal cortex.The distribution density of the PV-positive neurons in the VPA animals decreased significantly in both the hippocampus and medial frontal cortex compared to the normal animals.The subsequent environment enrichment,however,reversed these changes in the density of PV-positive neurons induced by VPA.The further analysis showed that the observed reversal in the density of the PV-positive neurons in the medial frontal cortex was mainly attributed to changes in the III,V and VI layers.Neither VPA exposure nor the subsequent environment enrichment affected the distribution density of SOM-positive neurons in both the hippocampus and medial prefrontal cortex.These results in an animal model suggest that environment enrichment can reverse VPA-induced deficits in learning and memory function,and this reversal is probably associated with changes in PV-positive inter-neurons in both the hippocampus and medial prefrontal cortex.