Zhang Guanghao

A model of injury potential for myelinated nerve fiber

Excellent models have been described in literatures which related membrane potential to extracellular electric or magnetic stimulation and which described the formation and propagation of action potentials along the axon, for both myelinated and nonmyelinated fibers. There is not, however, an adequate model for nerve injury which allows to compute the distribution of injury potential, a direct current potential difference between intact and injured nerve, because its importance has been ignored in the shadow of the well-known action potential. This paper focus on the injury potential and presents a model of the electrical properties of myelinated nerve which describes the time course of events following injury. The time-varying current and potential at all nodes can be computed from the model, and the factors relate to the amplitude of injury potential can be determined. It is shown that the amplitude of injury potential decreased gradually with injury time, and the recession curve was exponential. Results also showed that the initial amplitude of injury potential is positively related to the grade of injury and fiber diameter. This model explained the mechanism of formation of injury potential and can provide instruction for applied electric field to prevent the formation injury potential.

Influence of low-frequency rTMS on EEG of epileptic rats

The present research was to study the influence of low-frequency rTMS on epilepsy by EEG analysis. A train of 100, 0.5 Hz rTMS was applied on 15 Sprague-Dawley rats, and sham stimulation was also applied. EEG was recorded before stimulation and within 1 minute after rTMS and sham stimulation. Results showed that mean absolute power (MAP) of gamma band and relative power (RP) of beta and gamma band decreased significantly after low-frequency rTMS. In another experiment, pentylenetetrazol was injected immediately after 100 impulses of 0.5 Hz rTMS. Results showed that seizure susceptibility decreased greatly. These results indicate that low-frequency rTMS has certain suppressive effects on epilepsy due to power spectrum reduction.