Peripheral stimulation affects subthreshold Triple Stimulation Technique.
L Caranzano1, M A Stephan2, M Bedulli2
1Neurology Service, Department of Clinical Neurosciences, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland; Faculté de Biologie et de Médecine, Doctoral School, Université de Lausanne, Lausanne, Switzerland.
Journal of Neuroscience Methods
|October 1, 2020
Summary
The triple stimulation technique (TST) does not reliably detect more peripheral motor neuron discharges than conventional transcranial magnetic stimulation (TMS) at subthreshold intensities. TST can be confounded by peripheral stimulation effects.
Area of Science:
- Neuroscience
- Neurophysiology
- Motor Control
Background:
- Conventional transcranial magnetic stimulation (TMS) can be affected by desynchronization and phase cancellation, limiting its sensitivity in quantifying motor evoked potentials (MEPs).
- The triple stimulation technique (TST) was proposed as a more sensitive method to overcome these limitations in TMS.
Purpose of the Study:
- To investigate whether sub-threshold TMS, when combined with TST, can evoke peripheral motor neuron discharges (MNs).
- To compare the number of MEPs elicited by TMS versus TST at sub-threshold intensities.
- To assess the potential confounding effects of peripheral stimulation on TST.
Main Methods:
- Fifteen healthy participants received both TMS and TST at 80% resting motor threshold.
- A subgroup of five participants underwent a peripheral stimulation control condition to isolate TST effects.
- Comparison of MEPs elicited by conventional TMS and TST was performed.
Main Results:
- TST at sub-threshold TMS intensities did not significantly detect more cortical responses compared to conventional TMS.
- Peripheral supra-maximal stimuli in the TST condition introduced confounding effects that mimicked cortical responses.
- TST did not show increased detection of spinal MN discharges at subthreshold TMS intensities.
Conclusions:
- At sub-threshold TMS intensities, TST does not offer superior detection of spinal MN discharges compared to conventional TMS.
- TST is susceptible to confounding effects from peripheral stimulation, particularly near threshold intensities.
- While TST may assess MN pool and corticospinal tract integrity, careful consideration of peripheral stimulation artifacts is crucial for paradigms like paired-pulse stimulation.
