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. 2013;8(3):e60293.
doi: 10.1371/journal.pone.0060293. Epub 2013 Mar 26.

Integration of sensory force feedback is disturbed in CRPS-related dystonia

Winfred Mugge  1 , Frans C T van der Helm, Alfred C Schouten
Affiliations

Integration of sensory force feedback is disturbed in CRPS-related dystonia

Winfred Mugge et al. PLoS One. 2013.

Abstract

Complex regional pain syndrome (CRPS) is characterized by pain and disturbed blood flow, temperature regulation and motor control. Approximately 25% of cases develop fixed dystonia. The origin of this movement disorder is poorly understood, although recent insights suggest involvement of disturbed force feedback. Assessment of sensorimotor integration may provide insight into the pathophysiology of fixed dystonia. Sensory weighting is the process of integrating and weighting sensory feedback channels in the central nervous system to improve the state estimate. It was hypothesized that patients with CRPS-related dystonia bias sensory weighting of force and position toward position due to the unreliability of force feedback. The current study provides experimental evidence for dysfunctional sensory integration in fixed dystonia, showing that CRPS-patients with fixed dystonia weight force and position feedback differently than controls do. The study shows reduced force feedback weights in CRPS-patients with fixed dystonia, making it the first to demonstrate disturbed integration of force feedback in fixed dystonia, an important step towards understanding the pathophysiology of fixed dystonia.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Experimental setup.
The subject controlled a haptic manipulator that simulated a spring. During reference trials the measured force was displayed together with the target force. During blind and catch trials the visual feedback was disabled. The subject operated a foot switch to indicate (s)he believed to have acquired the target force.
Figure 2
Figure 2. The measured forces in the three trial types against spring stiffness.
Mean force with error bars indicating standard deviation in CRPS-patients (left) and in controls (right). For reference, both panels are supplemented with the measured forces in the reference and blind trials with the infinitely stiff spring.
Figure 3
Figure 3. Force difference (ΔF) between the catch and the blind trials.
Mean force difference in CRPS-patients (solid) and in controls (dashed) with error bars indicating the standard error of the mean.
Figure 4
Figure 4. Sensory weighting of position feedback.
Mean position weights in CRPS-patients (solid) and in controls (dashed) with error bars indicating the standard error of the mean. Note that 1.0 implies only position weighting, while 0.0 implies only force weighting.
Figure 5
Figure 5. Sensory weighting of force feedback.
Mean force weights in CRPS-patients (solid) and in controls (dashed) with error bars indicating the standard error of the mean. Note that 1.0 implies only force weighting, while 0.0 implies only position weighting.
See this image and copyright information in PMC

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