The intermuscular 3–7 Hz drive is not affected by distal proprioceptive input in myoclonus-dystonia

Abstract

In dystonia, both sensory malfunctioning and an abnormal intermuscular low-frequency drive of 3–7 Hz have been found, although cause and effect are unknown. It is hypothesized that sensory processing is primarily disturbed and induces this drive. Accordingly, experimenter-controlled sensory input should be able to influence the frequency of the drive. In six genetically confirmed myoclonus-dystonia (MD) patients and six matched controls, the low-frequency drive was studied with intermuscular coherence analysis. External perturbations were applied mechanically to the wrist joint in small frequency bands (0–4, 4–8 and 8–12 Hz; ‘angle protocol) and at single frequencies (1, 5, 7 and 9 Hz; ‘torque’ protocol). The low-frequency drive was found in the neck muscles of 4 MD patients. In these patients, its frequency did not shift due to the perturbation. In the torque protocol, the externally applied frequencies could be detected in all controls and in the two patients without the common drive. The common low-frequency drive was not be affected by external perturbations in MD patients. Furthermore, the torque protocol did not induce intermuscular coherences at the applied frequencies in these patients, as was the case in healthy controls and in patients without the drive. This suggests that the dystonic 3–7 Hz drive is caused by a sensory-independent motor drive and sensory malfunctioning in MD might rather be a consequence than a cause of dystonia.

Quantifying connectivity via efferent and afferent pathways in motor control using coherence measures and joint position perturbations

“…Our results may appear different from the results in van der Meer et al (2010) who used a similar approach applying position perturbations to the wrist to investigate intermuscular drive in dystonia patients and healthy controls during an isotonic force task. In this study, no CMC was elicited in the healthy controls when position perturbations were applied.…”

“…Corticomuscular coherence has also been measured in a clinical setting to study movement disorders such as various types of tremor (van der Meer et al 2010;Grosse et al 2003;van Rootselaar et al 2006), including the tremor present in Parkinson's disease (Florin et al 2010;Amtage et al 2009). In addition, CMC has been proposed as an attractive measure of connectivity in motor control after stroke (Braun et al 2007;Fang et al 2009;Meng et al 2009;Yao and Dewald 2006).…”

Spasms after spinal cord injury show low-frequency intermuscular coherence

“…Intermuscular coherence at 3–10 Hz has also been reported in myoclonus dystonia, which is a movement disorder with a genetic basis ( Foncke et al 2007 ; Grosse et al 2004 ; van der Meer et al 2010 ). Similar to the spasms investigated in the present study, this is characterized by involuntary muscle contractions.…”

Identification of connectivity in human motor control: exciting the afferent pathways

“…However, van der Meer et al (2010) applied perturbations up to 12Hz while we applied a perturbation also including frequencies in the beta band. Williams and Baker (2009b) showed that Renshaw cell recurrent inhibition reduces oscillatory coupling at frequencies under approximately 10 Hz which may explain why van der Meer et al (2010) found no CMC. We argue, therefore, that to elicit CMC using a continuous perturbation, the perturbation signal should contain frequencies in the beta band.…”

“…Corticomuscular coherence has also been measured in a clinical setting to study movement disorders such as various types of tremor (van der Meer et al, 2010;Grosse et al, 2003;van Rootselaar et al, 2006), including the tremor present in Parkinson's disease (Florin et al, 2010b;Amtage et al, 2009). In addition, CMC has been proposed as an attractive measure of connectivity in motor control after stroke (Braun et al, 2007;Fang et al, 2009;Meng et al, 2009;Yao and Dewald, 2006).…”