Postural and kinetic coordination following cortical stimuli which induce flexion movements in the cat's limbs

The relationship between movement and the postural adjustment associated with it has been studied following flexion movements of a limb induced by cortical stimulation in chronically implanted cats. Variations in the vertical force exerted by each limb, as well as the displacement of the centre of gravity (projected onto the plane of stance), were investigated. It was established that: The pattern of postural adjustment observed in these conditions is diagonal; that is to say, flexion of one limb is accompanied by diminution in the vertical force exerted by the diagonally opposite limb and an increase in the force exerted by the other two. The displacement of the projected centre of gravity is sterotyped during the first phase of variation in forces. Its extent may be considered as an index of the efficiency of postural adjustment. The study of the latencies of the changes in force indicates, at least in the case of hindlimb movements, that postural adjustment is an active phenomenon and does not arise passively from the interplay of purely mechanical forces. In the same conditions, an analysis of the time course and latency of recorded changes in force indicates that postural adjustment is not triggered reflexly by the disequilibrium brought about by movement but is a result of a central nervous command.