Functional and structural neural bases of task specificity in isolated focal dystonia

Abstract

Background Task‐specific focal dystonias selectively affect movements during the production of highly learned and complex motor behaviors. Manifestation of some task‐specific focal dystonias, such as musician's dystonia, has been associated with excessive practice and overuse, whereas the etiology of others remains largely unknown. Objectives In this study, we aimed to examine the neural correlates of task‐specific dystonias in order to determine their disorder‐specific pathophysiological traits. Methods Using multimodal neuroimaging analyses of resting‐state functional connectivity, voxel‐based morphometry and tract‐based spatial statistics, we examined functional and structural abnormalities that are both common to and distinct between four different forms of task‐specific focal dystonias. Results Compared to the normal state, all task‐specific focal dystonias were characterized by abnormal recruitment of parietal and premotor cortices that are necessary for both modality‐specific and heteromodal control of the sensorimotor network. Contrasting the laryngeal and hand forms of focal dystonia revealed distinct patterns of sensorimotor integration and planning, again involving parietal cortex in addition to inferior frontal gyrus and anterior insula. On the other hand, musician's dystonia compared to nonmusician's dystonia was shaped by alterations in primary and secondary sensorimotor cortices together with middle frontal gyrus, pointing to impairments of sensorimotor guidance and executive control. Conclusion Collectively, this study outlines a specialized footprint of functional and structural alterations in different forms of task‐specific focal dystonia, all of which also share a common pathophysiological framework involving premotor‐parietal aberrations. © 2019 International Parkinson and Movement Disorder Society

Normal Temporal Discrimination in Musician's Dystonia Is Linked to Aberrant Sensorimotor Processing

“…Abnormalities in resting‐state function activity and connectivity in patients with musician's and nonmusician's dystonia were reported in our previous articles . In this study, voxelwise correlations between TDT z scores and resting‐state brain activity were examined within each group.…”

“…Taking into account these findings in healthy individuals, the correlations between temporal discrimination and inferior parietal activity as well as any other brain regions present in healthy individuals were lost in nonmusician's dystonia, likely leading to abnormally increased TDT in these patients. Abnormal structural organization, functional activity, and connectivity of the inferior parietal cortex, including the angular gyrus, have been increasingly implicated in the pathophysiology of focal hand dystonia and laryngeal dystonia . Vulnerable parietal–premotor functional connectivity has been associated with the polygenic risk of dystonia, whereas maladaptive plasticity of the inferior parietal cortex has been related to the loss of inhibition as a result of reduced gamma‐aminobutyric acid (GABA)‐ergic function .…”

“…All of the participants provided written informed consent, which was approved by the institutional review board of Partners HealthCare Research Program. Data from some participants were reported in our previous studies …”

A microstructural neural network biomarker for dystonia diagnosis identified by a DystoniaNet deep learning platform

“…Specifically, the biomarker components that were automatically learned by DystoniaNet as most informative for discriminating the disorder have been previously demonstrated to be aberrant in patients with dystonia. While gray matter changes appear to be more relevant to dystonia form-specific aberrations ( 29 – 32 ), white matter alterations across different forms of dystonia emerge as a more common feature of this disorder. Structural abnormalities in the corpus callosum were previously reported within the dystonia spectrum, including laryngeal dystonia, cervical dystonia, and blepharospasm, as well as focal hand dystonia, musician’s dystonia, X-linked dystonia-parkinsonism, and poststroke lingual dystonia (e.g., refs.…”

Parietal conditioning enhances motor surround inhibition

“…The anterior part of inferior parietal lobule (aIPL) has inhibitory control over the ipsilateral primary motor cortex (M1) [8] and is also involved in precision grasp [9]. Moreover, FHD patients exhibiting reduced mSI [3,10] also have aberrant parietal-premotor-motor functional connectivity [11,12]. Hence, we speculated that this inhibitory parietomotor network would influence mSI.…”