Abstract
A less precise force output impairs our ability to perform movements, learn new motor tasks, and use tools. Here we show that low-frequency oscillations in force are detrimental to force precision. We summarize the recent evidence that low-frequency oscillations in force output represent oscillations of the spinal motor neuron pool from the voluntary drive, and can be modulated by shifting power to higher frequencies. Further, force oscillations below 0.5 Hz impair force precision with increased voluntary drive, aging, and neurological disease. We argue that the low-frequency oscillations are (1) embedded in the descending drive as shown by the activation of multiple spinal motor neurons, (2) are altered with force intensity and brain pathology, and (3) can be modulated by visual feedback and motor training to enhance force precision. Thus, low-frequency oscillations in force provide insight into how the human brain regulates force precision.
Highlights
The force output always fluctuates around a mean value
We demonstrate that oscillations below 0.5 Hz are detrimental to force precision but the central nervous system (CNS) can modulate these oscillations by shifting power to higher frequencies
Force fluctuations are regarded as noise derived from various parts of the CNS and harmful to force precision
Summary
The force output always fluctuates around a mean value. This variability is detrimental to our ability to perform movements with accuracy, learn new motor skills, and use tools. We highlight that force fluctuations represent low-frequency oscillations of the spinal motor neuron pool from the descending drive. Lower limb contractions (e.g., ankle dorsiflexion; Kwon et al, 2011) These results suggest that the low-frequency oscillations are present in the force output regardless of the number or the type of effectors used. The force output, is not irregular (Gaussian noise) but highly rhythmical This rhythmicity may represent a strategy by the CNS to regulate the force output or a physiological oscillation that perturbs the motor command (see section below). The evidence that low-frequency oscillations in force are related to force precision is presented below
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