Objectives: Two experiments examine the motor coordination and anticipatory control during a grasping task in children with ASD to determine development and specificity of deficits.
Methods: Experiment 1 was quasi-experimental, contrasting ASD and typically developing (TD) groups (ages 8y2m -19y1m). Experiment 2 was quasi-experimental, contrasting autism, DD and TD groups., (ages 1y9m - 6y5m). Participants were recruited through an autism registry and collaborating projects/agencies. For both experiments, the dependent measures were onset latency between grip and load forces, grip force at the onset of load force, maximum grip force, and time to maximum grip force across three load categories (0.5N, 1.5N, and 3N). A pincer or three-jaw-chuck were used to grasp the experimental apparatus. Each subject performed 15 trials across 3 load categories (1N, 2N, and 4N). Data was processed and reduced using Datapac 2000. ANOVAs (group X load; group X load X age) were used to analyze the data..
Results: Experiment 1: Precision grip data were collected from 28 participants (ASD=14, TD =14), matched on chronological age and gender. Mean age was 11 years (range=8-19y). There was a significant main effect of group for grip to load force onset latency, F (1, 78) = 9.855, p = 0.002, and grip force at onset of load force, F (1, 75) = 9.056, p = 0.004. With respect to peak grip force, only the main effect for load was found to be significant, F (1, 78) = 5.737, p = 0.005. Similarly, for time to peak grip force only the main effect for load was significant F (1, 78) = 4.213, p = 0.018. Tukey's post hoc analysis revealed that for peak grip force and time to peak grip force 1 N load was significantly different from 4 N load, while the 2 N load was different from neither the 1 N nor the 4 N load categories. Experiment 2: Participants were 2-6 years (ASD=25; DD=13; TD=34 TD), matched on mental age. Analyses are in progress.
Conclusions: In Experiment 1, prolonged onset latencies indicated that during the initial phase of precision grip (i.e.prior to lift-off), participants with ASD exhibited serial control of grip and load forces as opposed to the parallel control demonstrated by their TD peers. After liftoff, participants with ASD exhibited a trend toward higher peak grip forces and longer time to peak grip forces compared to controls. The results of Experiment 2 will determine if abnormalities in precision grip are unique to autism as compared to DD and to what extent age is a mediating variable. Understanding the motor features of ASD will expand the diagnostic profile for persons with ASD and lead to more refined intervention strategies.