Effect of inactivation of the intermediate cerebellum on overground locomotion in the rat: a comparative study of the anterior and posterior lobes.

The importance of the cerebellum in control of locomotion is demonstrated by the ataxic gait of cerebellar patients. The intermediate cerebellum contains somatotopical representations for forelimbs and hindlimbs in both anterior and posterior lobes. However, it is not known whether these separate regions have discrete roles in control of limb movements during locomotion. Here we compared the effect of muscimol-induced inactivation of the anterior or posterior intermediate cerebellum on limb movements in walking rats. Inactivation of the anterior intermediate cerebellum had clear effects on limb movements during overground locomotion, resulting in excessive toe elevation and hyperflexion of joints in the swing phase. Inactivation of the posterior region resulted in similar but less pronounced deficits. Postural defects were not present in either group of rats. These findings suggest that the intermediate cerebellum of the anterior lobe has a greater influence on the ability to control limb movements during overground locomotion than the posterior lobe.