The objective of this study was to examine phase- and task-dependent modulation of stretch reflexes during repetitive finger movements in writer's cramp, and compare them with normal controls from our previous study. A subject with writer's cramp conducted two rhythmic tasks, index finger abduction (RFA) and a pen-squeezing (RPS) task akin to handwriting. Stretch reflexes were evoked by mechanical perturbations at random phases of each task. Surface electromyograms (EMG) were recorded from two hand muscles, first dorsal interosseous (FDI) and flexor digitorum superficialis (FDS). The reflex response and background EMG activity of each muscle were modulated in a phase-dependent manner in both tasks. However, they varied largely in phase during the RFA task, but in approximately inverse phase-relationship during RPS. Reflex sensitivity, as represented by the slope of the linear regression between response and background, was much lower for both muscles in the 'writing' task (RPS) than in the RFA task with its positively correlated responses. These phase- and task-related modulation patterns differed dramatically from those observed in our control subjects, where reflex responses were modulated largely in phase with background activity and reflex sensitivity was much higher, particularly in FDI during RFA and FDS during RPS. The altered reflex modulation patterns in writer's cramp may reflect deficiencies of integration of proprioceptive afferent inputs and reduced inhibition at cortical and spinal levels during writing performance. Results from this case study support clinically identified task-specific feature of focal hand dystonia.
We test two fundamental tenets of the theory of fixed income: (i) the
Stock market variations and the yield changes should be anti-correlated; (ii)
The change in central bank rates, as a proxy of the monetary policy of the
Central bank, should be a predictor of the future stock market direction. Usi...
At 1 year a novel reflex arc with stimulation of the appropriate dermatome was seen in the majority of subjects. Improvements in voiding and bowel function were noted. Lower extremity weakness was mostly self-limited, except in 1 subject with a persistent foot drop. More patients and longer followup...
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