Visuomotor Adaptation Deficits in Patients with Essential Tremor

Abstract

Essential tremor (ET) is a progressive movement disorder whose pathophysiology is not fully understood. Current evidence supports the view that the cerebellum is critically involved in the genesis of the tremor in ET. However, it is still unknown whether cerebellar dysfunction affects not only the control of current movements but also the prediction of future movements through dynamic adaptation toward a changed environment. Here, we tested the capacity of 28 patients with ET to adapt in a visuomotor adaptation task known to depend on intact cerebellar function. We found specific impairments in that task compared to age-matched healthy controls. Adaptation to the visual perturbation was disrupted in ET patients, while de-adaptation, the phase after abrupt removal of the perturbation, developed similarly to control subjects. Baseline tremor-independent motor performance was as well similar to healthy controls, indicating that adaptation deficits in ET patients were not rooted in an inability to perform goal-directed movements. There was no association between clinical severity scores of ET and early visuomotor adaptation abilities. These results provide further evidence that the cerebellum is dysfunctional in ET.

Impairments of motor adaptation in Essential Tremor are linked to movement execution

“…Our results are consistent with previous adaptation studies performed with ET patients in various tasks (Bindel et al, 2022;Chen et al, 2006;Hanajima et al, 2016;Kronenbuerger et al, 2007). Here we reproduced the results of Chen et al (Chen et al, 2006), and added to this line of evidence that the impairment in adaptation in ET patients may reflect a general sensorimotor deficit as it also impacts the visual system despite the absence of ET symptoms in unperturbed saccades (Helmchen et al, 2003;Wójcik-Pȩdziwiatr et al, 2016).…”

“…The copyright holder for this preprint (which this version posted April 21, 2023. ; https://doi.org/10.1101/2023.04.21.537795 doi: bioRxiv preprint [4] Given the involvement of cerebellum in sensorimotor adaptation and its putative link with tremor, previous works studied adaptation in cohorts of ET patients. Generally, these patients were able to adapt to perturbations, but to a lesser extent than healthy volunteers in various tasks including adaptation to force field, visuomotor and prism adaptation, as well as eyeblink conditioning (Chen et al, 2006;Bindel et al, 2022;Hanajima et al, 2016;Kronenbuerger et al, 2007). Considering that sensorimotor adaptation may involve multiple components (Mathew & Crevecoeur, 2021), we aimed to better understand the mechanisms at the origin of this motor adaptation deficit using two sensorimotor adaptation tasks probing visual and upper limb motor systems.…”

Neurophysiology of cerebellar ataxias and gait disorders

“…Visuomotor adaptation deficits in other neurological disorders may therefore point to a cerebellar role in the underlying pathology. For instance, a visuomotor adaptation study in essential tremor patients found specific impairments in adaptation to a visual perturbation which were not associated with an inability to perform goal-directed movements, thus corroborating a cerebellar dysfunction hypothesis underlying ET ( Hanajaima et al, 2016 , Bindel et al, 2022 ). On the other hand, intact visuomotor adaptation found in patients with cervical dystonia may provide evidence for deficits along the cortico-basal-ganglia loop rather than cerebellar involvement in dystonia ( Loens et al, 2021 ).…”