Neostriatal stimulation activates tongue-protruder muscle, but not tongue-retractor or facial muscles: an electrical and chemical microstimulation study in rats

Whether electrical microstimulation of a rat's striatal jaw region (SJR) in fact induced tongue or facial muscle activity in addition to jaw muscle ac tivity was tested. Microstimulation of SJR-evoked EMG activity in a jaw-ope ner (anterior digastricus) and tongue-protruder (genioglossus). No activity was evoked in jaw-dosers (temporalis or masseter), tongue-retractor (hyogl ossus) or in facial muscles. In addition, the EMG effect could still be ind uced after extensive ablation of the neocortex; it was reproduced by microi njection of 50 mM kainic acid into SJR. The effective sites were histologic ally localized to a small central striatal region adjoining the anterior co mmissure. These findings may be of considerable value in understanding the striatal mechanism of orolingual dyskinesia involving involuntary jaw and t ongue movements. (C) 2001 Elsevier Science B.V. All rights reserved.