Neuroscience Seminar : A representation of effort in decision making and movement control
Dr Alaa A. Ahmed, Associate Professor (Department of Integrative Physiology and Department of Mechanical Engineering, University of Colorado Boulder)
Thursday, 14 July 2016, 1pm to 2pm
C113 Weiskrantz Room, Department of Experimental Psychology
Hosted by Tamar Makin (firstname.lastname@example.org)
Abstract: Decisions depend on the reward at stake and the effort required. However, these same variables influence the vigor of the ensuing movement, suggesting that factors that affect evaluation of action also influence performance of the selected action. In this talk, I will describe a mathematical framework that links decision-making with motor control. Each action has a utility, i.e. cost function, that combines the reward at stake with its effort requirements, both discounted as a hyperbolic function of time. The critical assumption of this model is to represent effort via the metabolic energy expended to produce the movement. This energetic representation describes a parameterization of effort as a function of movement duration, mass of the limb, distance, and force, which we confirmed experimentally in reaching movements. Our main result is to show that a single mathematical formulation of action, a utility describing the goodness of the movement via effort, reward, and time, predicts both the decisions that animals make as well as the vigor of the movements that follow. This framework accounts for choices that birds make in walking vs. flying, choices that people make in reaching and force production, and the curious fact that pedestrians walk faster in certain cities. We suggest that decision-making and movement control share a common utility in which the expected rewards and the energetic costs are discounted as a function of time.