Upper-Limb Movement Kinematics and Motor Proficiency Are Associated with the Severity of Autism Spectrum Disorder

Background: Although the core features of Autism Spectrum Disorder (ASD) are social impairment, communication abnormalities, and restricted and repetitive behaviors, fine and gross motor disturbances can present alongside core characteristics of the disorder and can have a significant impact on quality of life and social development (Lai et al., 2014). Quantitative methods, such as kinematic analysis, can describe precisely the spatial and temporal dimensions of the motor impairments associated with ASD, potentially identifying a well-defined motor phenotype within the spectrum.

Objectives: To investigate whether a group of school-aged, high functioning children with ASD would show abnormalities in kinematics of a simple reach-to-drop task. On the basis of our previous findings in a sample of preschool children with ASD (Forti et al., 2011, Crippa et al., 2015), we hypothesized that children with ASD would differ from typical developing peers in terms of the basic kinematics related to the second part of the movement, in which the participant transported the ball from a support to the target hole. In addition, to investigate whether, in our sample of individuals with ASD, kinematics abnormalities are linked with core clinical symptom severity, we correlated performance on this task and on other standardized motor measures with severity scores of ASD.

Methods: Fifteen children with ASD and twenty typically developing children (TD) aged between 6 and 12, matched by gender, age, and perceptual reasoning were enrolled. Three-dimensional kinematic data were collected by a motion-capture system based on eight infrared cameras during a simple reach-to-drop task. In addition, we assessed motor proficiency using the Movement Assessment Battery for Children—2 (MABC 2; Henderson et al., 2007), the Beery-Buktenica Developmental Test of Visual-Motor Integration (VMI; Beery and Beery, 2010) and an abbreviated battery of test from NEPSY-II (Korkman et al., 2007). The severity of ASD spectrum symptoms was measured with Social Responsiveness Scale (SRS; Constantino, 2002).

Results: Children with ASD showed lower peak of deceleration in the second part of movement (p<0.05), and scored significantly lower in MABC 2 and NEPSY-II (all p<0.05). The degree of clinical symptom severity was positively correlated with difficulties in balance, tapping, and with anomalous upper-limb kinematics all p<0.05).

Conclusions: These preliminary findings extend earlier investigations of our group (Forti et al., 2011; Crippa et al., 2015), depicting kinematics abnormalities also in children with ASD of school age. These peculiarities and other impairments in the motor domain are significantly associated with core clinical symptom severity of ASD.