THE UNOBSERVABILITY OF CENTRAL COMMANDS - WHY TESTING HYPOTHESES IS SO DIFFICULT

The experiments Feldman and Levin suggest do not definitively test the ir proposed solution to be problem of selecting muscle activations. Th eir test of the movement directions that elicit EMG activity can be in terpreted without regard to the form of the central commands, and thei r fast elbow flexion test is based on a forward computation that obscu res the insensitivity of the predicted trajectory to the details of th e putative commands.