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Effective Stimulation Type and Waveform for Force Control of the Motor Unit System: Implications for Intraspinal Microstimulation

Title
Effective Stimulation Type and Waveform for Force Control of the Motor Unit System: Implications for Intraspinal Microstimulation
Author(s)
Kim, HojeongJu, Youngchang
DGIST Authors
Kim, HojeongJu, Youngchang
Issued Date
2021-06
Type
Article
Author Keywords
stimulation waveformforce controlmotor unitneuromodulationintraspinal microstimulationstimulation type
Keywords
PERSISTENT INWARD CURRENTSMOTONEURONS IN-VIVOSPINAL MOTONEURONSELECTRICAL-STIMULATIONBISTABLE BEHAVIORCALCIUM CURRENTSMUSCLELENGTHMODELCAT
ISSN
1662-453X
Abstract
The input-output properties of spinal motoneurons and muscle fibers comprising motor units are highly non-linear. The goal of this study was to investigate the stimulation type (continuous versus discrete) and waveform (linear versus non-linear) controlling force production at the motor unit level under intraspinal microstimulation. We constructed a physiological model of the motor unit with computer software enabling virtual experiments on single motor units under a wide range of input conditions, including intracellular and synaptic stimulation of the motoneuron and variation in the muscle length under neuromodulatory inputs originating from the brainstem. Continuous current intensity and impulse current frequency waveforms were inversely estimated such that the motor unit could linearly develop and relax the muscle force within a broad range of contraction speeds and levels during isometric contraction at various muscle lengths. Under both continuous and discrete stimulation, the stimulation waveform non-linearity increased with increasing speed and level of force production and with decreasing muscle length. Only discrete stimulation could control force relaxation at all muscle lengths. In contrast, continuous stimulation could not control force relaxation at high contraction levels in shorter-than-optimal muscles due to persistent inward current saturation on the motoneuron dendrites. These results indicate that non-linear adjustment of the stimulation waveform is more effective in regard to varying the force profile and muscle length and that the discrete stimulation protocol is a more robust approach for designing stimulation patterns aimed at neural interfaces for precise movement control under pathological conditions.
URI
http://hdl.handle.net/20.500.11750/15404
DOI
10.3389/fnins.2021.645984
Publisher
Frontiers Media S.A.
Related Researcher
  • 김호정 Kim, Hojeong 바이오융합연구부
  • Research Interests Movement science; Neuromuscular physiology; Computational Medicine; Neural interface
Files in This Item:
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Appears in Collections:
Division of Biotechnology 1. Journal Articles

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