Serotonin transporter knockout in rats modulates category learning

Abstract

Lower function of the serotonin transporter (5-HTT) has a strong relationship with the development of autism spectrum disorder (ASD) in humans. One characteristic of ASD is the repetitive and restrictive behavior, which may form the basis for better memory and savant skills in some people with ASD. This characteristic in ASD may reflect a tendency towards an exploitation strategy rather than an exploration strategy during learning. Using a rat model, we developed a touchscreen-based task for testing 5-HTT knockout effects on stimulus category learning. By analyzing the data with a reinforcement learning drift diffusion model, we find that 5-HTT knockout rats show a lower learning rate and apply more of an exploitation versus exploration strategy compared to WT rats during category learning. The decision bound of decision-making during stimulus generalization indicates that more 5-HTT knockout rats than WT rats exploit irrelevant information to categorize stimuli. The touchscreen-based task we developed greatly increases the translational value from animals to humans and helps to understand the behavioral mechanisms underlying repetitive behavior in ASD.