Manual Motor Deficits in Autism Spectrum Disorders (ASD)

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder that affects social, cognitive and sensorimotor skills. This dissertation explores three specific behavioral studies that investigate the motor deficits in individuals with ASD. The first study investigates how force amplitude affects the output force in subjects with ASD and healthy individuals. For both the groups, the variability in the force output increased and the accuracy decreased with an increase in the force amplitude. Compared with control subjects, the subjects with ASD showed increased variability and reduced accuracy in their force output. The second study examines how a change in spatial features such as the visual gain affects output force variability and accuracy in healthy subjects and subjects with ASD. Both the groups showed a decrease in variability and an increase in accuracy with an increase in the visual gain. However, the subjects with ASD showed higher variability and reduced accuracy in their force output compared to the healthy individuals. The third study was designed to examine force adaptation characteristics in healthy individuals. During this study, the visual gain was altered during each trial and the force adaptation characteristics were examined during each trial. Significant group effects in first and second experiments suggested that the individuals with ASD demonstrated higher variability and lower accuracy in their sustained grip force output compared to healthy individuals. During the first study, significant group x force interactions were observed which suggested manual motor processing deficits in subjects with ASD, especially at higher force amplitudes. The group x gain interactions did not reach significance which suggested normal sensorimotor processing in subjects with ASD. The third study was designed to examine manual motor force adaptation characteristics in healthy subjects. The suggested experiment was designed to characterize typical healthy pattern of force adaptation due to visual gain modulation. The experiment can be used, in future, to identify any cerebellar abnormalities that might contribute to motor control deficits in ASD.