Grip-force variability in asymptomatic carriers of the Huntington gene – a biomarker for presymptomatic clinical studies?

The cerebellum, parietal cortex, and premotor cortex are integral to visuomotor processing. The parameters of visual information that modulate their role in visuomotor control are less clear. From motor psychophysics, the relation between the frequency of visual feedback and force variability has been identified as nonlinear. Thus we hypothesized that visual feedback frequency will differentially modulate the neural activation in the cerebellum, parietal cortex, and premotor cortex related to visuomotor processing. We used functional magnetic resonance imaging at 3 Tesla to examine visually guided grip force control under frequent and infrequent visual feedback conditions. Control conditions with intermittent visual feedback alone and a control force condition without visual feedback were examined. As expected, force variability was reduced in the frequent compared with the infrequent condition. Three novel findings were identified. First, infrequent (0.4 Hz) visual feedback did not result in visuomotor activation in lateral cerebellum (lobule VI/Crus I), whereas frequent (25 Hz) intermittent visual feedback did. This is in contrast to the anterior intermediate cerebellum (lobule V/VI), which was consistently active across all force conditions compared with rest. Second, confirming previous observations, the parietal and premotor cortices were active during grip force with frequent visual feedback. The novel finding was that the parietal and premotor cortex were also active during grip force with infrequent visual feedback. Third, right inferior parietal lobule, dorsal premotor cortex, and ventral premotor cortex had greater activation in the frequent compared with the infrequent grip force condition. These findings demonstrate that the frequency of visual information reduces motor error and differentially modulates the neural activation related to visuomotor processing in the cerebellum, parietal cortex, and premotor cortex.

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Grip Force Variability and Its Effects on Children’s Handwriting Legibility, Form, and Strokes

Journal of Biomechanical Engineering ◽

10.1115/1.4002611 ◽

2010 ◽

Vol 132 (11) ◽

Cited By ~ 14

Author(s):

Tiago H. Falk ◽

Cynthia Tam ◽

Heidi Schwellnus ◽

Tom Chau

Keyword(s):

Grip Force ◽

First Grade ◽

Second Grade ◽

Force Variability ◽

Writing Difficulties ◽

Force Dynamics ◽

Intervention Planning ◽

Underlying Processes ◽

Writing Task ◽

Shed Light

A comprehensive understanding of the underlying biomechanical processes during handwriting is needed to accurately guide clinical interventions. To date, quantitative measurement of such biomechanical processes has largely excluded measurements of the forces exerted radially on the barrel of the writing utensil (grip forces) and how they vary over time during a handwriting task. An instrumented writing utensil was deployed for a direct measurement of kinematic and temporal information during a writing task, as well as forces exerted on the writing surface and on the barrel of the pen. The writing utensil was used by a cohort of 35 students (19 males), 16 in first grade and 19 in second grade, as they performed the Minnesota Handwriting Assessment (MHA) test. Quantitative grip force variability measures were computed and tested as correlates of handwriting legibility, form, and strokes. Grip force variability was shown to correlate strongly with handwriting quality, in particular for students classified by the MHA as nonproficient writers. More specifically, static grip force patterns were shown to result in poor handwriting quality and in greater variation in handwriting stroke durations. Grip force variability throughout the writing task was shown to be significantly lower for nonproficient writers (t-test, p<0.01) while the number of strokes and per-stroke durations were shown to be higher (p<0.03). The results suggest that grip force dynamics play a key role in determining handwriting quality and stroke characteristics. In particular, students with writing difficulties exhibited more static grip force patterns, lower legibility and form scores, as well as increased variation in stroke durations. These findings shed light on the underlying processes of handwriting and grip force modulation and may help to improve intervention planning.

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Visual and proprioceptive feedback mechanisms of precision manual motor control in autism spectrum disorder

10.21203/rs.3.rs-387580/v1 ◽

2021 ◽

Author(s):

Robin L Shafer ◽

Zheng Wang ◽

James Bartolotti ◽

Matthew W. Mosconi

Keyword(s):

Autism Spectrum Disorder ◽

Visual Feedback ◽

Grip Force ◽

Motor Behavior ◽

Autism Spectrum ◽

Spectrum Disorder ◽

Proprioceptive Feedback ◽

Force Variability ◽

Tendon Vibration ◽

Motor Behaviors

Abstract Background Individuals with Autism Spectrum Disorder (ASD) show deficits processing sensory feedback to reactively adjust ongoing motor behaviors. Atypical reliance on visual and proprioceptive feedback each have been reported during motor behaviors in ASD suggesting that impairments are not specific to one sensory domain but may instead reflect a deficit in multisensory processing, resulting in reliance on unimodal feedback. The present study tested this hypothesis by examining motor behavior across different visual and proprioceptive feedback conditions during a visually guided precision grip force test. Methods Participants with ASD (N = 43) and age-matched typically developing (TD) controls (N = 23), range 10–20 years, completed a test of precision gripping. They pressed on force sensors with their index finger and thumb while receiving visual feedback on a computer screen in the form of a horizontal bar that moved upwards with increased force. They were instructed to press so that the bar reached the level of a static target bar and then to hold their grip force as steadily as possible. Visual feedback was manipulated by changing the gain of the force bar. Proprioceptive feedback was manipulated by applying 80 Hz tendon vibration at the wrist to induce an illusion of muscle elongation. Force variability (standard deviation) and irregularity (sample entropy) were examined using multilevel linear models. Results While TD controls showed increased force variability with the tendon vibration on compared to off, individuals with ASD showed similar levels of force variability across tendon vibration conditions. Individuals with ASD showed stronger age-associated reductions in force variability relative to controls across conditions. The ASD group also showed greater age-associated increases in force irregularity relative to controls, especially at higher gain levels and when the tendon vibrator was turned on. Conclusions Our findings that individuals with ASD show similar levels of force variability and regularity during induced proprioceptive illusions suggest a reduced ability to integrate proprioceptive feedback information to guide ongoing precision manual motor behavior. We also document stronger age-associated gains in force control in ASD relative to TD suggesting delayed development of multisensory feedback control of motor behavior.

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Initial action output and feedback-guided motor behaviors in autism spectrum disorder

Molecular Autism ◽

10.1186/s13229-021-00452-8 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Kathryn E. Unruh ◽

Walker S. McKinney ◽

Erin K. Bojanek ◽

Kandace K. Fleming ◽

John A. Sweeney ◽

...

Keyword(s):

Autism Spectrum Disorder ◽

Grip Strength ◽

Grip Force ◽

Feedforward Control ◽

Autism Spectrum ◽

Spectrum Disorder ◽

Force Variability ◽

Force Output ◽

Motor Behaviors ◽

Age Related

Abstract Background Sensorimotor issues are common in autism spectrum disorder (ASD), related to core symptoms, and predictive of worse functional outcomes. Deficits in rapid behaviors supported primarily by feedforward mechanisms, and continuous, feedback-guided motor behaviors each have been reported, but the degrees to which they are distinct or co-segregate within individuals and across development are not well understood. Methods We characterized behaviors that varied in their involvement of feedforward control relative to feedback control across skeletomotor (precision grip force) and oculomotor (saccades) control systems in 109 individuals with ASD and 101 age-matched typically developing controls (range: 5–29 years) including 58 individuals with ASD and 57 controls who completed both grip and saccade tests. Grip force was examined across multiple force (15, 45, and 85% MVC) and visual gain levels (low, medium, high). Maximum grip force also was examined. During grip force tests, reaction time, initial force output accuracy, variability, and entropy were examined. For the saccade test, latency, accuracy, and trial-wise variability of latency and accuracy were examined. Results Relative to controls, individuals with ASD showed similar accuracy of initial grip force but reduced accuracy of saccadic eye movements specific to older ages of our sample. Force variability was greater in ASD relative to controls, but saccade gain variability (across trials) was not different between groups. Force entropy was reduced in ASD, especially at older ages. We also find reduced grip strength in ASD that was more severe in dominant compared to non-dominant hands. Limitations Our age-related findings rely on cross-sectional data. Longitudinal studies of sensorimotor behaviors and their associations with ASD symptoms are needed. Conclusions We identify reduced accuracy of initial motor output in ASD that was specific to the oculomotor system implicating deficient feedforward control that may be mitigated during slower occurring behaviors executed in the periphery. Individuals with ASD showed increased continuous force variability but similar levels of trial-to-trial saccade accuracy variability suggesting that feedback-guided refinement of motor commands is deficient specifically when adjustments occur rapidly during continuous behavior. We also document reduced lateralization of grip strength in ASD implicating atypical hemispheric specialization.

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Visual and somatosensory feedback mechanisms of precision manual motor control in autism spectrum disorder

Journal of Neurodevelopmental Disorders ◽

10.1186/s11689-021-09381-2 ◽

2021 ◽

Vol 13 (1) ◽

Author(s):

Robin L. Shafer ◽

Zheng Wang ◽

James Bartolotti ◽

Matthew W. Mosconi

Keyword(s):

Autism Spectrum Disorder ◽

Visual Feedback ◽

Grip Force ◽

Motor Behavior ◽

Autism Spectrum ◽

Spectrum Disorder ◽

Force Variability ◽

Tendon Vibration ◽

Motor Behaviors ◽

Somatosensory Feedback

Abstract Background Individuals with autism spectrum disorder (ASD) show deficits processing sensory feedback to reactively adjust ongoing motor behaviors. Atypical reliance on visual and somatosensory feedback each have been reported during motor behaviors in ASD suggesting that impairments are not specific to one sensory domain but may instead reflect a deficit in multisensory processing, resulting in reliance on unimodal feedback. The present study tested this hypothesis by examining motor behavior across different visual and somatosensory feedback conditions during a visually guided precision grip force test. Methods Participants with ASD (N = 43) and age-matched typically developing (TD) controls (N = 23), ages 10–20 years, completed a test of precision gripping. They pressed on force transducers with their index finger and thumb while receiving visual feedback on a computer screen in the form of a horizontal bar that moved upwards with increased force. They were instructed to press so that the bar reached the level of a static target bar and then to hold their grip force as steadily as possible. Visual feedback was manipulated by changing the gain of the force bar. Somatosensory feedback was manipulated by applying 80 Hz tendon vibration at the wrist to disrupt the somatosensory percept. Force variability (standard deviation) and irregularity (sample entropy) were examined using multilevel linear models. Results While TD controls showed increased force variability with the tendon vibration on compared to off, individuals with ASD showed similar levels of force variability across tendon vibration conditions. Individuals with ASD showed stronger age-associated reductions in force variability relative to controls across conditions. The ASD group also showed greater age-associated increases in force irregularity relative to controls, especially at higher gain levels and when the tendon vibrator was turned on. Conclusions Our findings that disrupting somatosensory feedback did not contribute to changes in force variability or regularity among individuals with ASD suggests a reduced ability to integrate somatosensory feedback information to guide ongoing precision manual motor behavior. We also document stronger age-associated gains in force control in ASD relative to TD suggesting delayed development of multisensory feedback control of motor behavior.

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