Using threshold tracking, differences have been established between large myelinated sensory and α motor axons in humans. Major differences are that sensory axons are relatively depolarised at rest such that they have a greater persistent Na⁺ current, and have greater activity of hyperpolarisation-activated cyclic nucleotide-gated (HCN) channels. Sensory axons may thereby be protected from hyperpolarising stresses, and are less likely to develop conduction block. However, the corollary is that sensory axons are more excitable and more likely to become ectopically active.

Citations

• Strength-duration properties and excitability of motor and sensory axons across different target thresholds
  Yoshimitsu Shimatani, Cindy Shin-Yi Lin, José Manuel Matamala, Matthew C. Kiernan
  Journal of Neurophysiology.2023; 129(6): 1434.     CrossRef
• Does Essential Tremor Alter the Axonal Excitability Properties of Lower Motor Neurons?
  Yerim Kim, Young Eun Kim, Joo Young Lee, Hyeo-Il Ma, Soon Kyung Shim, Sun min Yoon, Jong Seok Bae
  Journal of Clinical Neurophysiology.2022; 39(6): 492.     CrossRef
• Autonomic and Somatic Nerve Functions in Type 2 Diabetes Mellitus Patients: Electrophysiological Aspects
  Anca Motataianu, Laura Barcutean, Zoltan Bajko, Adina Stoian, Smaranda Maier, Septimiu Voidazan, Rodica Balasa
  Diagnostics.2021; 11(11): 2005.     CrossRef
• Simulating perinodal changes observed in immune-mediated neuropathies: impact on conduction in a model of myelinated motor and sensory axons
  Boudewijn T. H. M. Sleutjes, Maria O. Kovalchuk, Naric Durmus, Jan R. Buitenweg, Michel J. A. M. van Putten, Leonard H. van den Berg, Hessel Franssen
  Journal of Neurophysiology.2019; 122(3): 1036.     CrossRef

Background
It is generally accepted that upper motor neuron (UMN) lesion can alter lower motor neuron (LMN) functionby the plasticity of neural circuit. However there have been only few researches regarding the axonal excitability of LMNafter UMN injury especially during the acute stage. The aim of this study was to investigate the nerve excitability propertiesof the LMNs following an acute to subacute supratentorial corticospinal tract lesion. Methods: An automated nerve excitabilitytest (NET) using the threshold tracking technique was utilized to measure multiple excitability indices in median motoraxons of 15 stroke patients and 20 controls. Testing of both paretic and non-paretic side was repeated twice, during theacute stage and subacute stage. The protocols calculated the strength-duration time constant from the duration?릀harge curve,parameters of threshold electrotonus (TE), the current-threshold relationship from sequential sub-threshold current, and therecovery cycle from sequential supra-threshold stimulation. Results: On the paretic side, compared with the control group,significant decline of superexcitablity and increase in the relative refractory period were observed during the subacute stageof stroke. Additionally, despite the absence of statistical significance, a mildly collapsing in (