PATTERN OF ACTIVITY IN MUSCLES OF SHOULDER AND ELBOW DURING FORELIMB REACHING IN THE RAT

Forelimb reaching by rats is commonly used as a model motor performance for neurophysiological investigations into the control of skilled limb movements. However, the activities of muscles involved in the task have not been previously described. The aim of this study was to identify the relationships between muscles of the shoulder and elbow in terms of the timing of activitY onset during performance of fore-limb reaching movements in the rat. The results showed that reach-related activity in flexor muscles of the shoulder can precede attainment of the goal of the movement (grasping of food) by 400 ms or more, with activity in elbow muscles occurring within 100 ms of food grasp. These data highlight the importance of EMG recordings in interpreting recordings from brain structures during movement, since the early muscle activity recorded here is considerably in advance of reach-associated neural activity previously recorded in rats, that was assumed to be related to movement preparation.