Luc P.J. Selen (Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, The Netherlands ) | Deciding, acting and adapting in an uncertain world

Abstract

We act on uncertain information in an ever changing world with an unreliable motor system. Here I will present a number of studies investigating how we deal with uncertainty, change and unreliability, trying to maintain stable interactions with our environment. First I will argue that there is a continuous flow of perceptual evidence to the motor system to prepare for possible action outcomes (Selen, Shadlen and Wolpert, 2012) and possibly changes-of-mind. In this work I use classic stretch reflexes of muscles to probe the state of the motor system in preparation for action based on a noisy stream of evidence. Second I will talk about ongoing work on the sophisticated interplay between vestibular inputs and task specification in goal-directed arm movement. It has been shown that both visually (e.g. Franklin and Wolpert 2008) and proprioceptively (Pruszynski, Kurtzer and Scott, 2008) elicited reflex behaviour is extremely dependent on task instruction. Here we galvanic vestibular stimulation to induce a vestibular perturbation that is reflexively compensated for in goal directed reaching. Finally, I will present an experimental and modelling study on how the brain tries to keep multiple internal models about environmental dynamics separated and how this influences learning and generalization curves. Subjects had to learn two opposing force fields simultaneously and we varied the spatial separation between the two targets associated with the two fields. Our motor primitives and adaptation model suggests that the tuning width of the primitives decreases with decreasing target separation. Furthermore, updating of the primitives’ weights seems to move from movement-referenced to plan-referenced (Gonzalez-Castro et al., 2011) with decreasing target separation.