Interaction of Evoked Cortical Potentials in the Rabbit
There have previously been several studies of the interaction of evoked cortical potentials. When paired electrical stimuli of differing intervals were applied to the superficial radial nerve, it was apparent that the evoked cortical potentials of the sensorimotor area exhibited an absolute and a relative inexcitability. With comparatively light anesthesia, there was also apparent an afterdischarge corresponding to an oscillatory decrease in the excitability . In the monkey and in the cat, if direct cortical stimulation were used as the conditioning stimuli and brief sounds were used as the test stimuli and the time course of changes of evoked potentials from the auditory area were examined, a post-excitatory depression as well as oscillatory excitability changes corresponding to the afterdischarge were also seen, such that corresponding to the positive waves of the afterdischarge, cortical excitability decreased . Under the latter experimental conditions, although the mutual interaction of conditioning and test stimuli which results if subcortical afferent systems are employed is avoided, direct cortical stimulation is far from a normal means of activation of the cortex. Consequently, we have presented conditioning and test stimuli to the two somatosensory nerves of different somatic levels, respectively, so that the above-mentioned experimental deficiency could be overcome to some degree, since the extent of the mutual interference of their afferent pathways subcortically is very small. Moreover, utilizing nerves of different somatic levels facilitates the investigation of the spatial aspects of cortical excitability changes as well as features of changes of cortical excitability evoked by different afferent nerves, and similar questions. This paper reports some observations obtained by using this method in rabbits.
KeywordsConditioning Stimulus Test Stimulus Radial Nerve Sural Nerve Test Response
Unable to display preview. Download preview PDF.
- 1.Jarcho, L. W., Excitability of cortical afferent systems during barbiturate anesthesia, J. Neurophysiol., 12:447–457 (1949).Google Scholar
- 2.Chang, H.-T., Changes in excitability of the cerebral cortex following a single electric shock applied to the cortical surface, J. Neurophysiol., 14:95–111 (1951).Google Scholar
- 3.Chang, H.-T., Similarity in action between curare and strychnine on cortical neurons, J. Neurophysiol., 16:221–233 (1953).Google Scholar