Functional and structural asymmetry in primary motor cortex in Asperger syndrome: a navigated TMS and imaging study

Abstract

Motor functions are frequently impaired in Asperger syndrome (AS). In this study, we examined the motor cortex structure and function using navigated transcranial magnetic stimulation (nTMS) and voxel-based morphometry (VBM) and correlated the results with the box and block test (BBT) of manual dexterity and physical activity in eight boys with AS, aged 8-11 years, and their matched controls. With nTMS, we found less focused cortical representation areas of distinct hand muscles in AS. There was hemispheric asymmetry in the motor maps, silent period duration and active MEP latency in the AS group, but not in controls. Exploratory VBM analysis revealed less gray matter in the left postcentral gyrus, especially in the face area, and less white matter in the precentral area in AS as compared to controls. On the contrary, in the right leg area, subjects with AS displayed an increased density of gray matter. The structural findings of the left hemisphere correlated negatively with BBT score in controls, whereas the structure of the right hemisphere in the AS group correlated positively with motor function as assessed by BBT. These preliminary functional (neurophysiological and behavioral) findings are indicative of asymmetry, and co-existing structural alterations may reflect the motor impairments causing the deteriorations in manual dexterity and other motor functions commonly encountered in children with AS.

Atypical Integration of Sensory-to-Transmodal Functional Systems Mediates Symptom Severity in Autism

“…This pattern also revealed significant associations with repetitive/restricted behaviors. Our results join the line of accumulating evidence that repetitive/restricted behaviors are related to deficits in the motor cortex ( 93 – 95 ), suggesting high specificity of our connectopic gradient for brain-symptom mapping. ASD-specific anomalies in the gradient organization were also found in the foveal and peripheral fields of V1, which patterns follow the main direction of the eccentricity observed in the retinotopic mapping.…”

Reduced asymmetry of the hand knob area and decreased sensorimotor u-fiber connectivity in middle-aged adults with autism

“…Our finding of increased right PrChand volume in middle-aged and older adults with ASD is consistent with previous reports of increased grey matter density in right pericentral cortex at the level of the hand knob in younger adults with ASD (DeRamus & Kana, 2015;Ecker et al, 2012). Our findings of reduced asymmetry in PrChand and PoChand volumes are also consistent with previous unilateral findings of increased right and/or decreased left grey matter density and volume in the pre-and postcentral gyri in ASD (Cauda et al, 2011;DeRamus & Kana, 2015;Ecker et al, 2012;Mahajan et al, 2016;Nickl-Jockschat et al, 2012;Säisänen et al, 2019), which may be interpreted in the context of reduced asymmetry. To our knowledge, morphological asymmetry has only been examined in a few studies on ASD Herbert et al, 2005;Postema et al, 2019).…”

Atypical representation of sensorimotor cortex in a patient with autism and epilepsy confirmed by direct electrocortical stimulation

“…Moreover, increased activation in prefrontal and parietal areas during motor learning tasks was demonstrated in ASD patients compared to non-autistic control subjects [9] . A navigated transcranial magnetic stimulation (nTMS) study in individuals with Asperger syndrome found less focused cortical organization of individual hand muscles as compared to healthy controls [16] .…”