Mechanisms of supraspinal correction of scratching generator

The influences of signals in descending systems on the parameters of scratching generator activity were studied on decerebrate immobilized cats. It was shown that phasic electric stimulation of descending systems evoked certain phase-dependent reorganization of the parameters of scratching generator efferent activity. Maximum increase in scratching cycle duration during electric stimulation of Deiters' nucleus, red nucleus and pyramidal tract is observed during stimulation in the first half of aiming phase. Stimulation in the second half of aiming phase and at the beginning of scratching jerk phase virtually does not change the scratching cycle duration. Maximum increase in scratching cycle duration during electric stimulation of the nucleus reticularis gigantocellularis is observed in the second half of aiming phase. Electric activation of descending pathways during aiming phase increases its intensity and decreases the intensity of scratching jerk phase. Activation of descending pathways during scratching jerk phase increases its intensity and virtually does not change the aiming phase intensity. Influences of electric activation of descending systems on scratching generator work reveal dependence on limb position. They are increased when the limb is deflected to the rear and are decreased during over-aimed position. Decerebellation leads to a decrease of scratching generator activity parameters rearrangement under influence of electric stimulation of the red nucleus and nucleus reticularis gigantocellularis, and to its increase during Deiters' nucleus stimulation. On the basis of these results the principles of supraspinal correction of scratching generator work are discussed.