[Natural head-forelimb coordination in dogs after vestibular de-afferentation]

We studied the influence of the vestibular lesion on the natural head--forelimb coordination. This coordination exists in intact dogs at the early stage of acquisition of the instrumental feeding reaction of tonic forelimb flexion in order to hold a cup with meat during eating when the head is bent down to foodwell. In untrained dogs, the forelimb flexion is preceded by lifting the head bent down to the food; the following lowering of the head leads to extension of the flexed forelimb. For performing the instrumental reaction, the innate coordination has to be rearranged into the opposite one. It is achieved only by learning. After the lesion of the primary motor cortex contralateral to the "working" forelimb in trained dogs, the innate coordination reappears, whereas the learned coordination breaks down steadily. It was shown that bilateral vestibular lesion do not disturb the innate coordination in intact dogs at the early stage of learning and in trained dogs after the motor cortex lesion. It was concluded that the studied natural head--forelimb coordination is not connected with the vestibular reflex.