PMID-13969854[0] Control and Training of Individual Motor Units
- humans have the ability to control the firing rate of peripheral motor units with a high resolution.
- "The quality of control over anterior horn cells may determine the rates of learning" yup!
- "Some learn such esquisite control that they soon can produce rhythms of contraction in one unit, imitating drum rolls etc"
- the youngest persons were among both the best and worst learners.
- after about 30 minutes the subject was required to learn how to repress the first unit and to recruit another one.
- motor unit = anterior horn cell, its axon, and all the muscle fibers on which the terminal branches of the axon end. max rate ~= 50hz.
- motor units can be discriminated, much like cortical neurons, by their shape.
- some patients could recruit 3-5 units altogether - from one bipolar electrode!
- in playback mode (task: trigger the queried unit), several subjects had particular difficulty in recruiting the asked-for units. "They groped around in their conscious efforts to find them sometimes, it seemed, only succeded by accident"
- some patients could recruit motor units in the absence of feedback, but they were unable to explain how they do it.
- 0.025 (25um) nylon-insulated Karma alloy EMG recording wire.
- feedback: auditory & visual (oscilloscope).
- motor units have a maximum rate, above which overflow takes place and other units are recruited (in accord with the size principle).
- "The controls (are) learned so quickly, are so esquisite, are so well retained after the feedbacks are eliminated that one must not dismiss them as tricks"
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