Increased Force Variability Is Associated with Altered Modulation of the Motorneuron Pool Activity in Autism Spectrum Disorder (ASD)

Abstract

Force control deficits have been repeatedly documented in autism spectrum disorder (ASD). They are associated with worse social and daily living skill impairments in patients suggesting that developing a more mechanistic understanding of the central and peripheral processes that cause them may help guide the development of treatments that improve multiple outcomes in ASD. The neuromuscular mechanisms underlying force control deficits are not yet understood. Seventeen individuals with ASD and 14 matched healthy controls completed an isometric index finger abduction test at 60% of their maximum voluntary contraction (MVC) during recording of the first dorsal interosseous (FDI) muscle to determine the neuromuscular processes associated with sustained force variability. Central modulation of the motorneuron pool activation of the FDI muscle was evaluated at delta (0–4 Hz), alpha (4–10 Hz), beta (10–35 Hz) and gamma (35–60 Hz) frequency bands. ASD patients showed greater force variability than controls when attempting to maintain a constant force. Relative to controls, patients also showed increased central modulation of the motorneuron pool at beta and gamma bands. For controls, reduced force variability was associated with reduced delta frequency modulation of the motorneuron pool activity of the FDI muscle and increased modulation at beta and gamma bands. In contrast, delta, beta, and gamma frequency oscillations were not associated with force variability in ASD. These findings suggest that alterations of central mechanisms that control motorneuron pool firing may underlie the common and often impairing symptoms of ASD.

Static and dynamic postural control deficits in aging fragile X mental retardation 1 (FMR1) gene premutation carriers

“…Our findings of reduced COP ML complexity ( α exponent of DFA measure was within the range from 1.5 to 2 indicating increased long-range correlation and reductions in COP ML complexity) in premutation carriers are consistent with previous studies documenting progressive decay of lateral postural sway associated with spinocerebellar and cerebellar-brainstem circuitry decline in Friedreich’s ataxia [13]. Evidence of reductions in COP variability in target directions and in stochastic processes of lateral sway in FMR1 premutation carriers each suggest atypical deterioration of dynamic postural control mechanisms involved in modulating center of mass movement in relation to the base of support [21, 34] .…”

“…Importantly, cerebellar inputs from neocortical regions are critical to the cerebellum’s role in integrating internal and external sensory feedback information in order to dynamically calibrate motor output. Greater motor variability [34, 47, 48] and reduced sensorimotor complexity [49] each have been demonstrated in individuals with disorders affecting the cerebellum. The postural control deficits reported here in premutation carriers thus may provide important indices of cerebellar mechanisms contributing to clinical issues in individuals with FMR1 premutations.…”

“…The COP time series were derived from the force and moment data for each standing posture [22]. The variability of individuals’ postural sway was quantified using COP standard deviation in both the AP (COP AP ) and ML (COP ML ) directions as we did previously [34].…”

Resting-State Brain Network Dysfunctions Associated With Visuomotor Impairments in Autism Spectrum Disorder

“…Our group has documented that individuals with ASD show increased force variability relative to typically developing (TD) controls during visually guided precision gripping (Mosconi et al, 2015; Wang et al, 2015) and isometric index finger abduction (Wang et al, 2017). Precision force control is essential for manual dexterity, and increased grip force variability is associated with diminished capacity to execute manual motor tasks such as writing, buttoning clothes, and manipulating small or delicate items (Potter et al, 2009).…”

Effect of Visual-Cueing on Two-Legged Hopping Variability in Children With Autism Spectrum Disorder: A Pilot Study

“…Although visual feedback has been proposed as a strategy to improve motor control in children with ASD (Somogyi et al 2016), visuomotor integration deficits are a relatively consistent finding in this population (Masterton and Biederman 1983;Haswell et al 2009;Dowd et al 2012;Greffou et al 2012;Papadopoulos et al 2012;Ament et al 2015;Nebel et al 2016;Sharer et al 2016). Furthermore, there is evidence that children with ASD show impaired integration of visual cueing and feedback to modulate ongoing fine-motor Wang et al 2015Wang et al , 2017 and gross-motor commands (Nayate et al 2012), with increased visuomotor integration demands associated with increased variability of motor output compared to TD children. Individuals with ASD also show deficits during whole-body gross motor tasks involving multi-modal integration of auditory and proprioception sources (Moran et al 2013).…”