Zur bedeutung des menschlichen kleinhirns fur die anpassung posturaler reflexmuster an wechselnde breiten der standflache: 'Ankle'-und 'hip'- strategie

The aim of the present study was to investigate the role of the human cerebellum in postural adaptation for changes in the width of the support surface following backward translations. Standing on a flat surface, healthy subjects usually activate dorsal and distal leg muscles in response to backward translations ('ankle'-strategy). Standing on a small beam, ventral and proximal leg muscles are activated more frequently ('hip'-strategy). 'Ankle'-and 'hip'-strategies are the extremes of a continuum of possible postural reflex strategies. A total of 6 patients with isolated lesions of the cerebellum and 6 sexy-and age-matched controls were tested. Both control and cerebellar subjects changed postural strategies with changes in the width of the support surface. Most control subjects demonstrated 'ankle'-strategies while standing on the flat surface and 'mixed'-strategies while standing on the beam. In contrast, most cerebellar subjects utilized 'mixed'-strategies while standing on the flat surface and 'hip'-strategies while standing on the narrow beam. The more frequent use of ventral and proximal muscles might reflect a compensatory mechanism for postural hypermetria in cerebellar subjects.