Strategy of arm movement control is determined by minimization of neural effort for joint coordination

Abstract

Optimality criteria underlying organization of arm movements are often validated by testing their ability to adequately predict hand trajectories. However, kinematic redundancy of the arm allows production of the same hand trajectory through different joint coordination patterns. We therefore consider movement optimality at the level of joint coordination patterns. A review of studies of multi-joint movement control suggests that a 'trailing' pattern of joint control is consistently observed during which a single ('leading') joint is rotated actively and interaction torque produced by this joint is the primary contributor to the motion of the other ('trailing') joints. A tendency to use the trailing pattern whenever the kinematic redundancy is sufficient and increased utilization of this pattern during skillful movements suggests optimality of the trailing pattern. The goal of this study is to determine the cost function minimization of which predicts the trailing pattern. We show that extensive experimental testing of many known cost functions cannot successfully explain optimality of the trailing pattern. We therefore propose a novel cost function that represents neural effort for joint coordination. That effort is quantified as the cost of neural information processing required for joint coordination. We show that a tendency to reduce this 'neurocomputational' cost predicts the trailing pattern and that the theoretically developed predictions fully agree with the experimental findings on control of multi-joint movements. Implications for future research of the suggested interpretation of the trailing joint control pattern and the theory of joint coordination underlying it are discussed.

Perceptual suboptimality: Bug or feature?

“…In particular, the cost of neural effort for information processing should be taken into account (Dounskaia & Shimansky 2016;. Decision making is based on processing sensory information and integrating it with internal representations of past experience.…”

Minimum Torque Change Model Vs. Power Law for Elliptic Movements

“…If the human motor control system prefers the constancy of some parameters, for example the+ Dealt with in this study, relevant to the production of a movement in motor planning to the optimization of criterion functions, that is often hard to achieve, it allows us to conjecture the easiness of computation (Karniel, 2013;Dounskaia, 2016), as the criterion that the human motor control system respects in motor planning. It has to be made clear, how such mathematical parameters that are assumed to be constant, during a movement are interpreted in the biological system.…”

Advancing rational analysis to the algorithmic level

“…Finally, an application of the principle of the neurocomputational cost minimization to human movement control suggests that a learning process contributes to emergence of strategies that minimize the use of cognitive resources. This hypothesis is supported, for example, by an observation that more skillful movement performance is associated with the use of a more pronounced trailing joint control pattern, that is, the more intensive use of passive torques and spinal neural circuitries for production of training joint motion (Dounskaia and Shimansky 2016).…”

“…Multiple studies have demonstrated the trailing joint control pattern during various types of arm movements (for review, see Dounskaia 2005;. As discussed by Dounskaia and Shimansky (2016), this pattern is a result of movement optimization, which is apparent from a tendency to maximally exploit passive torques for rotation of the trailing joint and from an observation that the contribution of passive torques to control of the trailing joint increases with development of skill. Dounskaia and Shimansky (2016) used the information theory to show that the trailing pattern decreases the neurocomputational cost by reducing the amount of information that needs to be processed for joint coordination.…”