Skip to main content
Journal cover image

Isolating two sources of variability of subcortical stimulation to quantify fluctuations of corticospinal tract excitability.

Publication ,  Journal Article
Goetz, SM; Howell, B; Wang, B; Li, Z; Sommer, MA; Peterchev, AV; Grill, WM
Published in: Clin Neurophysiol
June 2022

OBJECTIVE: Investigate the variability previously found with cortical stimulation and handheld transcranial magnetic stimulation (TMS) coils, criticized for its high potential of coil position fluctuations, bypassing the cortex using deep brain electrical stimulation (DBS) of the corticospinal tract with fixed electrodes where both latent variations of the coil position of TMS are eliminated and cortical excitation fluctuations should be absent. METHODS: Ten input-output curves were recorded from five anesthetized cats with implanted DBS electrodes targeting the corticospinal tract. Goodness of fit of regressions with a conventional single variability source as well as a dual variability source model was quantified using a Schwarz Bayesian Information approach to avoid overfitting. RESULTS: Motor evoked potentials (MEPs) through DBS of the corticospinal tract revealed short-term fluctuations in excitability of the targeted neuron pathway reflecting endogenous input-side variability at similar magnitude as TMS despite bypassing cortical networks. CONCLUSION: Input-side variability, i.e., variability resulting in changing MEP amplitudes as if the stimulation strength was modulated, also emerges in electrical stimulation at a similar degree and is not primarily a result of varying stimulation, such as minor coil movements in TMS. More importantly, this variability component is present, although the cortex is bypassed. Thus, it may be of spinal origin, which can include cortical input from spinal projections. Further, the nonlinearity of the compound variability entails complex heteroscedastic non-Gaussian distributions and typically does not allow simple linear averages in statistical analysis of MEPs. As the average is dominated by outliers, it risks bias. With appropriate regression, the net effects of excitatory and inhibitory inputs to the targeted neuron pathways become noninvasively observable and quantifiable. SIGNIFICANCE: The neural responses evoked by artificial stimulation in the cerebral cortex are variable. For example, MEPs in response to repeated presentations of the same stimulus can vary from no response to saturation across trials. Several sources of such variability have been suggested, and most of them may be technical in nature, but localization is missing.

Duke Scholars

Altmetric Attention Stats
Dimensions Citation Stats

Published In

Clin Neurophysiol

DOI

EISSN

1872-8952

Publication Date

June 2022

Volume

138

Start / End Page

134 / 142

Location

Netherlands

Related Subject Headings

  • Transcranial Magnetic Stimulation
  • Pyramidal Tracts
  • Neurology & Neurosurgery
  • Motor Cortex
  • Humans
  • Evoked Potentials, Motor
  • Electrodes, Implanted
  • Bayes Theorem
  • 3209 Neurosciences
  • 17 Psychology and Cognitive Sciences
 

Citation

APA
Chicago
ICMJE
MLA
NLM
Goetz, S. M., Howell, B., Wang, B., Li, Z., Sommer, M. A., Peterchev, A. V., & Grill, W. M. (2022). Isolating two sources of variability of subcortical stimulation to quantify fluctuations of corticospinal tract excitability. Clin Neurophysiol, 138, 134–142. https://doi.org/10.1016/j.clinph.2022.02.009
Goetz, Stefan M., Bryan Howell, Boshuo Wang, Zhongxi Li, Marc A. Sommer, Angel V. Peterchev, and Warren M. Grill. “Isolating two sources of variability of subcortical stimulation to quantify fluctuations of corticospinal tract excitability.Clin Neurophysiol 138 (June 2022): 134–42. https://doi.org/10.1016/j.clinph.2022.02.009.
Goetz SM, Howell B, Wang B, Li Z, Sommer MA, Peterchev AV, et al. Isolating two sources of variability of subcortical stimulation to quantify fluctuations of corticospinal tract excitability. Clin Neurophysiol. 2022 Jun;138:134–42.
Goetz, Stefan M., et al. “Isolating two sources of variability of subcortical stimulation to quantify fluctuations of corticospinal tract excitability.Clin Neurophysiol, vol. 138, June 2022, pp. 134–42. Pubmed, doi:10.1016/j.clinph.2022.02.009.
Goetz SM, Howell B, Wang B, Li Z, Sommer MA, Peterchev AV, Grill WM. Isolating two sources of variability of subcortical stimulation to quantify fluctuations of corticospinal tract excitability. Clin Neurophysiol. 2022 Jun;138:134–142.
Journal cover image

Published In

Clin Neurophysiol

DOI

EISSN

1872-8952

Publication Date

June 2022

Volume

138

Start / End Page

134 / 142

Location

Netherlands

Related Subject Headings

  • Transcranial Magnetic Stimulation
  • Pyramidal Tracts
  • Neurology & Neurosurgery
  • Motor Cortex
  • Humans
  • Evoked Potentials, Motor
  • Electrodes, Implanted
  • Bayes Theorem
  • 3209 Neurosciences
  • 17 Psychology and Cognitive Sciences