Sensorimotor Deficits in Individuals with Autism Spectrum Disorder and Their Unaffected Biological Parents

Background: Sensorimotor impairments are highly prevalent in individuals with autism spectrum disorder (ASD), and reduced precision of eye movements in unaffected parents and siblings of individuals with ASD also has been documented. The degrees to which sensorimotor impairments are present across oculomotor and manual motor systems in unaffected parents and are familial have not yet been determined.

Objectives: 1) To examine the precision of eye movements and manual force in individuals with ASD and their biological parents, and 2) to determine whether sensorimotor abilities are inter-correlated among individuals with ASD and their parents.

Methods: We studied 48 probands with ASD and 102 parents of individuals with ASD (ASD parents). Among the probands and parents, 34 family trios were studied (i.e., proband and each biological parent). Thirty-three typically developing (TD) controls were matched with probands on age (range: 4-27 years), gender ratio, and nonverbal IQ. An additional 47 TD controls were matched with ASD parents on age, sex and IQ. Participants completed a visually-guided saccade (VGS) task in which they fixated on a central cue, and made rapid eye movements (i.e., saccades) to peripheral targets presented at ± 12 and 24 degrees from center. Participants also completed a sustained precision grip force task in which they pressed opposing load cells with their thumb and index finger while they viewed a static red/green target bar and a white force bar that moved upwards with increased force. They were instructed to press when the target bar turned green so that the white bar reached the level of the target bar and hold it there as steadily as possible for 8 seconds. Participants completed the precision force task at 15%, 45%, and 85% of their maximum force.

Results: During the VGS task, probands showed reduced saccade accuracy compared to controls at 24 deg. ASD parents showed greater saccade error variability compared to controls at 24 deg. During precision gripping, probands’ force was less accurate than controls during their initial pressing and when they sustained their force during the trial. ASD parents also were less accurate than controls during their initial pressing. Data collection is complete, and analysis of the familiality of sensorimotor issues in ASD is ongoing.

Conclusions: Our findings indicate that reductions in the precision of eye movements and manual motor behaviors previously documented in individuals with ASD also are present in unaffected biological parents suggesting that these deficits may be familial. Importantly, these deficits include reduced precision of both rapid movements controlled by predictive motor control processes as well as sustained motor behaviors guided by sensory feedback processes. These studies implicate multiple distinct sensorimotor control processes in the pathophysiology of ASD that may be important new targets for family genetic studies.