Low-frequency stimulation reverses kindling-induced neocortical motor map expansion

Abstract

Repeated application of low-frequency stimulation can interrupt the development and progression of seizures. Low-frequency stimulation applied to the corpus callosum can also induce long-term depression in the neocortex of awake freely moving rats as well as reduce the size of neocortical movement representations (motor maps). We have previously shown that seizures induced through electrical stimulation of the corpus callosum, amygdala or hippocampus can expand the topographical expression of neocortical motor maps. The purpose of the present study was to determine if low-frequency stimulation administered to the corpus callosum could reverse the expansion of neocortical motor maps induced by seizures propagating from the hippocampus. Adult Long-Evans hooded rats were electrically stimulated in the right ventral hippocampus, twice daily until 30 neocortical seizures were recorded. Subsequently, low-frequency stimulation was administered to the corpus callosum once daily for 20 sessions. High-resolution intracortical microstimulation was then utilized to derive forelimb-movement representations in the left (un-implanted) sensorimotor neocortex. Our results show that hippocampal seizures result in expanded motor maps and that subsequent low-frequency application can reduce the size of the expanded motor maps. Low-frequency stimulation may be an effective treatment for reversing seizure-induced reorganization of brain function.