MONOSYNAPTIC IA PATHWAYS AND MOTOR BEHAVIOR OF THE CAT DISTAL FORELIMB

The projection pattern from large muscle spindle afferents (Ia) onto c at alpha-motoneurones innervating the elbow, wrist and digit muscles i s correlated with new electromyographical and x-ray kinematic data on the motor behaviour of the forelimb. This correlation suggests that th e Ia-synergistic groups may be one substrate to organize movement comp onents mobilized in motor behaviour. This hypothesis is based on the d ata on the active stabilization of the radio-ulnar joints during the s tance phase, on the data on the Ia-organization of a motor nucleus tak ing part in different motor behaviours and on the results showing how the Ia convergence onto the long digit extensor muscles fits the execu tion of finely tuned movements at ball joints.