Studies on the human spontaneous electromyelogram (EMyeloG). III. Spontaneous spinal cord activity of the cat relevant to the human spontaneous EMyeloG.

The spontaneous electromyelogram (EMyeloG) was investigated in 16 cats, some after laminectomy and some by a percutaneous intrathecal technique similar to the human approach. Small diphasic negative-positive waves at less than 50 microV, with short durations, were consistently recorded from the posterior aspect of the spinal cord in both laminectomized and intact cats. It was demonstrated that this kind of background activity is mainly located within the posterior halves of the spinal cord and is strictly dependent on the peripheral inputs producing excitability changes in the gray matter of the posterior horn. Monophasic positive waves of larger amplitude were often recorded from the anterior halves of the spinal cord in both types of recording. However, the amplitude of the background activity of spontaneous EMyeloG was smaller in the percutaneous approach and negative sharp waves (NSWs) of large amplitude were never seen in these intact cats. NSWs were only observed in the majority of the laminectomized cats and were facilitated after spinalization. It was proposed that when the central and peripheral nervous system are intact in awake states, it is impossible to see NSWs either in human subjects or in cats.