Decreased dynamical complexity during quiet stance in children with autism spectrum disorders.

BACKGROUND: Postural control deficits in individuals with Autism Spectrum Disorders (ASD) are widely acknowledged; however, the underlying biomechanical features of these deficits remain unknown. Nonlinear analyses provide insight into the nature of how movement is controlled and have the potential to provide new insight into the postural control abnormalities associated with ASD. The purpose of this study was to further investigate postural control deficits in children with ASD through linear and nonlinear analyses of center of pressure (COP) data. METHODS: We evaluated COP data during quiet standing for 16 children with ASD and 17 age-matched typically developing (TD) children. The magnitude of COP fluctuations (COP ranges, velocity, and sway area) and complexity of postural control dynamics, quantified by multiscale entropy (MSE), were compared across groups. RESULTS: Children with ASD displayed larger fluctuations in their COP data, observed in COP ranges (95.5% mediolaterally and 46.9% anteroposteriorly, p<0.05 respectively) and COP sway area (885%, p<0.05). Children with ASD also displayed less complexity in their COP data, observed in the MSE complexity index (CI) (32.4% mediolaterally and 35.7% anteroposteriorly, p<0.05 respectively). CONCLUSIONS: The present study successfully revealed that children with ASD have more repetitive patterns in their COP data, indicating a less complex control of posture, on multiple time scales, during quiet stance. These findings suggest a more regular or restricted control of posture and may be an initial step in linking postural instability to stereotypic behavior and the neurobiology of ASD.

Decreased static and dynamic postural control in children with autism spectrum disorders.

The purpose of this study was to investigate postural control in children with Autism Spectrum Disorders (ASD) during static and dynamic postural challenges. We evaluated postural sway during quiet stance and the center of pressure (COP) shift mechanism during gait initiation for 13 children with ASD and 12 age-matched typically developing (TD) children. Children with ASD produced 438% greater normalized mediolateral sway (p<0.05) and 104% greater normalized anteroposterior sway (p<0.05) than TD children. Consequently, normalized sway area was also significantly greater (p<0.05) in the group with ASD. Similarly, the maximum separation between the COP and center of mass (COM) during quiet stance was 100% greater in the anteroposterior direction (p<0.05) and 146% greater in the resultant direction (p<0.05) for children with ASD. No significant difference was observed in the mediolateral direction, in spite of the 123% greater separation detected in children with ASD. During gait initiation, no group differences were detected in the posterior COP shift mechanism, suggesting the mechanism for generating forward momentum is intact. However, significantly smaller lateral COP shifts (p<0.05) were observed in children with ASD, suggesting instability or an alternative strategy for generating momentum in the mediolateral direction. These results help to clarify some discrepancies in the literature, suggesting an impaired or immature control of posture, even under the most basic conditions when no afferent or sensory information have been removed or modified. Additionally, these findings provide new insight into dynamic balance in children with ASD.

Performance of children with autism spectrum disorders on the dimension-change card sort task.

Restricted and repetitive behaviors in autism spectrum disorders have been conceptualized to reflect impaired executive functions. In the present study, we investigated the performance of 6-17-year-old children with and without an autism spectrum disorder on a dimension-change card sort task that explicitly indicated sorting rules on every trial. Diagnostic groups did not differ in speed of responses after the first rule switch or in speed or accuracy on blocks with mixed versus single sort rules. However, performance of the ASD group was significantly slower and less accurate overall than the typically-developing group. Furthermore, within the ASD group, poorer DCCS task performance did not predict more severe autism symptoms. Implications for the executive dysfunction theory of autism are discussed.

Duration judgments in children with ADHD suggest deficient utilization of temporal information rather than general impairment in timing.

Clinicians, parents, and teachers alike have noted that individuals with ADHD often have difficulties with "time management," which has led some to suggest a primary deficit in time perception in ADHD. Previous studies have implicated the basal ganglia, cerebellum, and frontal lobes in time estimation and production, with each region purported to make different contributions to the processing and utilization of temporal information. Given the observed involvement of the frontal-subcortical networks in ADHD, we examined judgment of durations in children with ADHD (N = 27) and age- and gender-matched control subjects (N = 15). Two judgment tasks were administered: short duration (550 ms) and long duration (4 s). The two groups did not differ significantly in their judgments of short interval durations; however, subjects with ADHD performed more poorly when making judgments involving long intervals. The groups also did not differ on a judgment-of-pitch task, ruling out a generalized deficit in auditory discrimination. Selective impairment in making judgments involving long intervals is consistent with performance by patients with frontal lobe lesions and suggests that there is a deficiency in the utilization of temporal information in ADHD (possibly secondary to deficits in working memory and/or strategy utilization), rather than a problem involving a central timing mechanism.