White Matter Differences Correlate with Social and Emotional Deficits in Autism

Children with autism spectrum disorders (ASD) exhibited differences in white matter diffusivity corresponding to autism-specific social and emotional deficits unrelated to motor impairments when compared with children with developmental coordination disorder (DCD). These are the findings of a study published in the journal Scientific Reports.

White matter studies indicate that many white matter differences found in ASD may correlate to motor impairments instead of core ASD symptoms, including social and communication deficits.

Researchers in the United States sought to understand specific white matter signatures in children with ASD (n=22) besides those associated with motor impairments and differentiate them from white matter signatures in children with DCD (n=16) and typically developing youth (n=22). The mean age of participants was 11 years (range, 8-17 years).

Researchers used the Total Movement Assessment Battery for Children-2 (MABC-2) to measure motor skills and identify motor deficits in children and adolescence aged 3-16 years. A higher score total score on the MABC-2 indicates better functioning. The total scores for each group were as follows: 5.76 for children in the ASD group, 4.31 for children in the DCD group, and 10.57 for children in the control group.

The Florida Apraxia Battery modified for children (FAB-2) was also used to assess motor development.

To measure social skills, the researchers used the Social Responsivity Scale (SRS Total), a survey completed by a parent or guardian of a child that generates a total score (T-score; 50 is the mean; T-scores ≤59 not tied to ASD) to determine social deficit severity in ASD. SRS Total scores were 77.45, 55.81, and 45.95, for children in the ASD group, the DCDC group, and the control group.

In addition, the researchers collected data using diffusion weighted magnetic resonance imaging (MRI), comparing radial, axial, and mean diffusivity as well as quantitative anisotropy between the 3 groups of children.

They discovered that children with ASD demonstrated white matter diffusivity differences in the mid-cingulum’s longitudinal and u-fibers, the corpus callosum forceps minor/anterior commissure, and the left middle cerebellar peduncle when compared with children in the other 2 groups.

Reduced diffusivity within the longitudinal fibers of the cingulum, especially the bilateral front-parietal and left parolfactory cingulum fibers, correlated with autism severity and alexithymia. White matter differences in the u-fibers of the cingulum suggested reduction of long-distance functional connectivity, affecting emotional, language, sensory, and autonomic processes.

Researchers speculated that diffusivity differences in the corpus callosum forceps minor/anterior commissure correlated with social deficits, a hallmark of ASD. Anomalies in the left middle cerebellar peduncle correlated significantly with autism severity.

Children with autism also demonstrated unique white matter diffusivity differences in the right inferior frontal occipital/extreme capsule, which correlated with autism severity, particularly difficulties with communication and interpretation of facial expressions, and genu of the corpus callosum, which correlated with difficulties verbalizing emotions, compared with typically developing children.

In contrast, children with DCD displayed unique abnormalities within the left cortico-spinal and cortico-pontine tracts when compared with children in the other 2 groups. These tracts strongly correlated with motor deficits predominant in DCD.  

“… [T]his is the first study to identify the fronto-parietal and the parolfactory portions of the cingulum as well as the anterior caudal u-fibers as specific to core ASD symptomatology and not related to motor-related comorbidity.”

Study limitations included decreased within-group variability, small sample size, and lack of generalizability of results outside of right-handed youth between the ages of 8 and 18.

This article originally appeared on Neurology Advisor