Stereotyped skeletal configurations of cervical column and rest to motion transition underly the motor repertoire in rodents.

During forward locomotion, guinea pigs adopted a posture which, although di fferent, was as stereotyped as at rest. The whole extent of the vertebral c olumn was extended, parallel to the earth-horizontal plane. This result sup ports the hypothesis that, in mammals, gaze and postural control by the cen tral nervous system would be simplified by the adoption of a limited number of skeletal configurations. They would be optimized for energy saving, bio mechanical efficacy and limitation of the number of degrees of freedom of t he skeletal apparatus. Transition between rest and forward locomotion displ ayed two prominent characteristics: the head was stabilized versus space th roughout the whole transition and the modifications of the skeletal geometr y were confined to the median plane and to two major articular regions. Suc h an organization revealed a fourth characteristic of the guinea pig postur al control: the skeletal configurations retained by evolution would ensure that smooth transitions take place between rest and the various activities of its motor repertoire. Finally, our purely descriptive data shed new ligh t on the architecture of the neuronal network which underlies the vestibula r control of gaze and posture. (C) 2001 Editions scientifiques et medicales Elsevier SAS.