Objective: To identify behavioral differences of motor sequence representation in persons with dystonia.

Background: Dystonia is a movement disorder characterized by variable twisting postures and movements that have been attributed to an inability to inhibit competing motor patterns or programs. A motor program is a representation of a movement that facilitates automatic motor control and aids in motor learning. However, it is unknown whether persons with dystonia use movement strategies that allow them to create, update, retain, and access new motor sequence representations.

Methods: Adults with dystonia and healthy controls performed finger tapping tasks where different visual stimuli prompted the same finger movements. At the conclusion of each tapping sequence, subjects were verbally probed for awareness that the motor sequence was identical across blocks. Awareness indicated that a subject was able to create and retain a representation of that sequence throughout performance of the task. We compared awareness, error rate, inter-tap-interval, savings (measured as faster improvement on subsequent presentations of a motor sequence), and smoothness between the dystonia and control groups. A Generalized Procrustes Analysis of the velocity-acceleration plot of each fingertip was used to compare variability in movement trajectories.

Results: There were no differences in performance parameters between people with dystonia and controls, but individuals with dystonia were less likely than controls to obtain awareness of the common motor sequence. Within the control group, higher procrustes values were the best predictor of awareness, indicating that control subjects who used a motor strategy of consistent finger movements were more likely to gain awareness than control subjects who did not use this strategy. However, subjects with dystonia that used this strategy were still unlikely to develop sequence awareness.

Conclusions: Movement consistency has been attributed to automatic control processes and is known to increase the quality and reliability of a sequence representation. Indivdiuals with dystonia were less likely to develop sequence awareness than were controls despite similar tapping consistency, indicating that people with dystonia might not be able to access this representation during motor performance.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/abnormal-motor-sequence-representation-in-dystonia/