Objectives: To determine whether neural reward systems (e.g. orbitofrontal cortex (OFC), amygdala, insular cortex, ventral striatum) are active when individuals with ASD view images related to their restricted interests, relative to a visual baseline, and whether the BOLD response in these areas was greater in a group of children with ASD than a control group whose members have a regular hobby.
Methods: Nine children with ASD and seven children with TD, ages 8-17, completed the study. Children and parents were given a questionnaire to assess hobbies and activities engaged during spare time. Parents were given the Yale Special Interests Interview (Volkmar and Klin, 1996) to assess the presence and severity of restricted interest. Information from the interview and questionnaires was used to create an “Own Interest” image stimulus set. Several of each child’s “Own Interest” images were pooled to create an “Others’ Interest” stimulus set for use as a visual baseline. This provided consistency between conditions in image complexity and size. A block design was implemented in 5 runs, each containing 15 presentations of each condition. Image processing and analysis was performed in SPM5; contrast maps were created for each subject and entered into a group level model. Regions of interest were chosen to include bilateral amygdala, OFC, insula, and nucleus accumbens. Percent signal change in these regions were correlated with variables obtained from the ADI-R and ADOS, the Yale Special Interest Interview, and an operant behavioral “button press” task, in which subjects used key presses to control the display time of images in both categories, yielding a quantitative measure of the reward value of the images. After the scan, recognition memory was tested for each subject to ensure that they attended to the images in each condition.
Results: Both individuals with ASD and controls showed activation in OFC, amygdala, and insular regions in the “Own Interest – Others’ Interest” contrast. This difference was significantly greater in the ASD group for the insula and OFC. Percent signal change extracted from this region correlated with differential display time in the operant button press task.
Conclusions: Although behavioral sciences have long since established that restricted interests are rewarding for individuals with ASD, this study provides the first neurobiological evidence that neural reward pathways are involved in restricted interests.