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Intracellular contribution to extracellularly recorded waveforms: the 'membrane rent' hypothesis
D Dumitru1, J C King, W E Rogers
1University of Texas Health Science Center at San Antonio, Department of Rehabilitation Medicine, 78284-7798, USA.
Summary
Simulations suggest complex muscle fiber waveforms in denervated tissue may arise from needle electrodes recording both intracellular and extracellular potentials. This
Area of Science:
- Neuroscience
- Biophysics
- Computational Biology
Background:
- Complex muscle fiber waveforms in electromyography (EMG) can be challenging to interpret.
- Simultaneous recording of intracellular and extracellular potentials is a potential source of waveform complexity.
Purpose of the Study:
- To investigate if simulated muscle fiber action potentials, incorporating an electrode-induced 'rent' in the sarcolemma, can reproduce complex clinical waveforms.
- To differentiate the origins of complex waveforms in innervated versus denervated muscle tissue.
Main Methods:
- Utilized published intracellular action potentials from healthy and denervated rat skeletal muscle.
- Developed a single muscle fiber computer simulation to model electrode-induced sarcolemmal 'rent' or crush effects.
- Generated and summed simulated extracellular and intracellular waveforms to match clinical observations.
Main Results:
- Simulations could not reproduce complex waveforms from innervated muscle fibers.
- Successfully simulated 12 out of 14 complex waveforms observed in denervated muscle tissue.
- The simulated waveforms in denervated tissue showed morphologies similar to clinically recorded potentials.
Conclusions:
- A 'rent' in the sarcolemma, allowing simultaneous recording of intracellular and extracellular potentials, may explain some complex waveforms in denervated muscle.
- This 'rent' hypothesis is unlikely to explain complex potentials in innervated muscle.
- The morphology of denervated action potentials might contribute to the success of the 'rent' hypothesis, rather than an actual tear. Further research is needed to confirm needle electrode capabilities in recording intracellular potentials without disruption.