Perception of the Length of Voluntary Movements

Background: Buccofacial Apraxia is defined as the inability to perform voluntary movements of the larynx, pharynx, mandible, tongue, lips and cheeks, while automatic or reflexive control of these structures is preserved. Buccofacial Apraxia frequently co-occurs with aphasia and apraxia of speech and it has been reported as almost exclusively resulting from a lesion of the left hemisphere. Recent studies have demonstrated the benefit of treating apraxia using motor training principles such as Augmented Feedback or Action Observation Therapy. In light of this, the study describes the treatment based on immersive Action Observation Therapy and Virtual Reality Augmented Feedback in a case of Buccofacial Apraxia. Participant and Methods: The participant is a right-handed 58-years-old male. He underwent a neurosurgery intervention of craniotomy and exeresis of infra axial expansive lesion in the frontoparietal convexity compatible with an atypical meningioma. Buccofacial Apraxia was diagnosed by a neurologist and evaluated by the Upper and Lower Face Apraxia Test. Buccofacial Apraxia was quantified also by a specific camera, with an appropriately developed software, able to detect the range of motion of automatic face movements and the range of the same movements on voluntary requests. In order to improve voluntary movements, the participant completed fifteen 1-hour rehabilitation sessions, composed of a 20-minutes immersive Action Observation Therapy followed by a 40-minutes Virtual Reality Augmented Feedback sessions, 5 days a week, for 3 consecutive weeks. Results: After treatment, participant achieved great improvements in quality and range of facial movements, performing most of the facial expressions (eg, kiss, smile, lateral angle of mouth displacement) without unsolicited movement. Furthermore, the Upper and Lower Face Apraxia Test showed an improvement of 118% for the Upper Face movements and of 200% for the Lower Face movements. Conclusion: Performing voluntary movement in a Virtual Reality environment with Augmented Feedbacks, in addition to Action Observation Therapy, improved performances of facial gestures and consolidate the activations by the central nervous system based on principles of experience-dependent neural plasticity.

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The primacy of rhythm: how discrete actions merge into a stable rhythmic pattern

Journal of Neurophysiology ◽

10.1152/jn.00587.2018 ◽

2019 ◽

Vol 121 (2) ◽

pp. 574-587 ◽

Cited By ~ 4

Author(s):

Zhaoran Zhang ◽

Dagmar Sternad

Keyword(s):

Building Blocks ◽

Periodic Pattern ◽

Voluntary Movements ◽

Rhythmic Pattern ◽

Rhythmic Movements ◽

Discrete Movements ◽

Floquet Multipliers ◽

Physiological Processes ◽

Rhythmic Behavior ◽

Virtual Target

This study examined how humans spontaneously merge a sequence of discrete actions into a rhythmic pattern, even when periodicity is not required. Two experiments used a virtual throwing task, in which subjects performed a long sequence of discrete throwing movements, aiming to hit a virtual target. In experiment 1, subjects performed the task for 11 sessions. Although there was no instruction to perform rhythmically, the variability of the interthrow intervals decreased to a level comparable to that of synchronizing with a metronome; furthermore, dwell times shortened or even disappeared with practice. Floquet multipliers and decreasing variability of the arm trajectories estimated in state space indicated an increasing degree of dynamic stability. Subjects who achieved a higher level of periodicity and stability also displayed higher accuracy in the throwing task. To directly test whether rhythmicity affected performance, experiment 2 disrupted the evolving continuity and periodicity by enforcing a pause between successive throws. This discrete group performed significantly worse and with higher variability in their arm trajectories than the self-paced group. These findings are discussed in the context of previous neuroimaging results showing that rhythmic movements involve significantly fewer cortical and subcortical activations than discrete movements and therefore may pose a computationally more parsimonious solution. Such emerging stable rhythms in neuromotor subsystems may serve as building blocks or dynamic primitives for complex actions. The tendency for humans to spontaneously fall into a rhythm in voluntary movements is consistent with the ubiquity of rhythms at all levels of the physiological system. NEW & NOTEWORTHY When performing a series of throws to hit a target, humans spontaneously merged successive actions into a continuous approximately periodic pattern. The degree of rhythmicity and stability correlated with hitting accuracy. Enforcing irregular pauses between throws to disrupt the rhythm deteriorated performance. Stable rhythmic patterns may simplify control of movement and serve as dynamic primitives for more complex actions. This observation reveals that biological systems tend to exhibit rhythmic behavior consistent with a plethora of physiological processes.

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