THE CONTROL OF MULTIJOINT MOVEMENTS RELIES ON DETAILED INTERNAL REPRESENTATIONS

This paper addresses the question what level of detail is required in internal representations used in control of multi-joint movements, foc using on contact control tasks. Following Bernstein, we define the cen tral problem to be which strategies are used in the nervous system in order to control the vastly redundant musculoskeletal system. Simplifi cations based on equilibrium point theories are rejected on the basis that when they are simple they do not lead to adequate behaviour, wher eas when they are complex they implicitly introduce the detailed inter nal representations that they were meant to dispense with. Based on bo th experimental data and on simulation results, it is argued that timi ng of muscle activation needs to be precisely tuned to the task at han d and the environmental conditions. It is argued that it is impossible to achieve this without detailed internal representations of the prop erties of the effector system in relation to the environment. It is at tempted to link Bernstein's notion of a hierarchical organization of t he nervous system in which tasks are delegated to subsystems as low as possible in the hierarchical structure of the central nervous system, to recent advances in neuroscience.