A reappraisal of rat motor cortex organization by intracortical microstimulation.

The organization of the motor cortex was reinvestigated with intracortical microstimulation, in light-anaesthetized (ketamine) rats. A posterolateral (PL) vibrissae area was found in addition to the rostral one, and blinks of the contralateral eyelids were elicited from a part of this PL area. Several cortical representations such as neck or tail were largely overlapping with neighbouring areas. Vegetative effects (mainly myosis and swallowing) were obtained from a medial cortical strip. Within the PL vibrissae area, a topical arrangement related to the vibrissal rows was observed, whereas in the leg areas, no individual representation of muscles could be evidenced. These results are compared with the maps previously published, and discussed in terms of specificity, musculotopy and overlapping of motor areas.