Publications by Year: 2019

The extrinsic risk and its association with neural alterations in spasmodic dysphonia
Laura de Lima Xavier and Kristina Simonyan. 2019. “The extrinsic risk and its association with neural alterations in spasmodic dysphonia.” Parkinsonism Relat Disord.Abstract
INTRODUCTION: Spasmodic dysphonia (SD) is an isolated focal dystonia characterized by laryngeal spasms during voluntary voice production. Environmental factors have been assumed to play a role in SD pathophysiology; however, the exact extrinsic risk factors and their association with neural alterations remain unknown. METHODS: A total of 186 SD patients and 85 healthy controls completed a structured 177-question survey, consisting of questions on general biographical information, medical history, symptomatology of dystonia. Data were imputed in a stepwise regression model to identify extrinsic risk factors for SD. In addition, functional MRI data from a subset of this cohort were analyzed to determine brain activation abnormalities associated with the SD extrinsic risk. RESULTS: We found that (1) recurrent upper respiratory infections, gastroesophageal reflux, and neck trauma, all of which influence sensory feedback from the larynx, represent extrinsic risk factors, likely triggering the manifestation of SD symptoms, and (2) neural alterations in the regions necessary for sensorimotor preparation and integration are influenced by an extrinsic risk in susceptible individuals. CONCLUSIONS: These findings provide evidence for the extrinsic risk in SD development and demonstrate the link with alterations in the sensorimotor preparatory network that collectively contribute to the multifactorial pathophysiology of SD.
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Top-down alteration of functional connectivity within the sensorimotor network in focal dystonia
Giovanni Battistella and Kristina Simonyan. 2019. “Top-down alteration of functional connectivity within the sensorimotor network in focal dystonia.” Neurology.Abstract
OBJECTIVES: To determine the directionality of regional interactions and influences of one region on another within the functionally abnormal sensorimotor network in isolated focal dystonia. METHODS: A total of 40 patients with spasmodic dysphonia with and without dystonic tremor of voice and 35 healthy controls participated in the study. Independent component analysis (ICA) of resting-state fMRI was used to identify 4 abnormally coupled brain regions within the functional sensorimotor network in all patients compared to controls. Follow-up spectral dynamic causal modeling (DCM) estimated regional effective connectivity between patients and controls and between patients with spasmodic dysphonia with and without dystonic tremor of voice to expand the understanding of symptomatologic variability associated with this disorder. RESULTS: ICA found abnormally reduced functional connectivity of the left inferior parietal cortex, putamen, and bilateral premotor cortex in all patients compared to controls, pointing to a largely overlapping pathophysiology of focal dystonia and dystonic tremor. DCM determined that the disruption of the sensorimotor network was both top-down, involving hyperexcitable parieto-putaminal influence, and interhemispheric, involving right-to-left hyperexcitable premotor coupling in all patients compared to controls. These regional alterations were associated with their abnormal self-inhibitory function when comparing patients with spasmodic dysphonia patients with and without dystonic tremor of voice. CONCLUSIONS: Abnormal hyperexcitability of premotor-parietal-putaminal circuitry may be explained by altered information transfer between these regions due to underlying deficient connectivity. Identification of brain regions involved in processing of sensorimotor information in preparation for movement execution suggests that complex network disruption is staged well before the dystonic behavior is produced by the primary motor cortex.
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Functional and structural neural bases of task specificity in isolated focal dystonia
Serena Bianchi, Stefan Fuertinger, Hailey Huddleston, Steven J Frucht, and Kristina Simonyan. 2019. “Functional and structural neural bases of task specificity in isolated focal dystonia.” Mov Disord.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.
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Recent advances in understanding the role of the basal ganglia
Kristina Simonyan. 2019. “Recent advances in understanding the role of the basal ganglia.” F1000Res, 8.Abstract
The basal ganglia are a complex subcortical structure that is principally involved in the selection and implementation of purposeful actions in response to external and internal cues. The basal ganglia set the pattern for facilitation of voluntary movements and simultaneous inhibition of competing or interfering movements. In addition, the basal ganglia are involved in the control of a wide variety of non-motor behaviors, spanning emotions, language, decision making, procedural learning, and working memory. This review presents a comparative overview of classic and contemporary models of basal ganglia organization and functional importance, including their increased integration with cortical and cerebellar structures.
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