Concurrent reinforcement in a valproic acid-induced animal model of autism, and environmental enrichment

Autism spectrum disorder (ASD) is a behavioral disorder characterized by dysfunction in social interactions, as well as hypersensitivity to sensory stimulation. Valproic acid (VPA), an anticonvulsant medication that has been shown to increase the risk of autism in humans, has become the standard for inducing a model of autism in animals. Some pathologies modeled in animals have been reversed using environmental enrichment paradigms. 84 Sprague-Dawley rats were used to test the effects of VPA and enrichment in a reinforcement paradigm across a three day pre-exposure period, followed by three days of sensory reinforcement (light), and finally three days of social reinforcement concurrent with light reinforcement on the opposite side of the testing chamber. A multifactorial analysis was conducted to assess the effects of the manipulations on absolute and relative responding across the three phases of testing. Introduction of the light stimulus increased responding proportionately more for VPA treated animals than controls; enrichment did not affect light responding. Upon introduction of the social reinforcer on the opposite side of the test apparatus, enrichment increased relative preference but not absolute responding for the social side; VPA had no effect. The two manipulations did not interact. The current model of VPA-induced autism in rats may lack ecological validity, given that a concurrent reinforcement paradigm extinguishes some of the effects of VPA.