The roles of various projection areas of the motor cortex in the reorganization of the natural coordination of head and forelimb movements in dogs

Abstract

A food-related operant reaction was developed in dogs, in which animals had to maintain tonic elevation of the forelimb to hold a bowl while eating with the head tilted towards the feeder. The acquisition of this reaction involved rearrangement of the natural coordination of head and limb movements which appeared at an early stage of training of the dogs. Forelimb elevation was initially accompanied by anticipatory raising of the head, while lowering of the head led to lowering of the elevated limb. Limb elevation could only be maintained in the posture in which the head was raised. The new coordination required for obtaining food, contrary to the innate coordination and consisting of tonic elevation of the limb with the head lowered, could only be achieved as a result of training. Previous studies have established that lesioning of the primary motor cortex (MI) in the hemisphere contralateral to the working limb leads to stable impairment of the learned coordination, with regression to the initial coordination. The present report describes studies of the effects of local lesions of various projection areas of MI on performance of the learned coordination. Dogs which had acquired the learned operant reaction requiring the new head/limb coordination showed impairment only after lesioning of the representation area of the working limb in the MI; lesioning of the representation area of the head had no such effect.