Biological Learning and Control ─ How the Brain Builds Representations, Predicts Events, and Makes Decisions

In Biological Learning and Control, Reza Shadmehr and SandroMussa-Ivaldi present a theoretical framework for understanding the regularity of the brain'sperceptions, its reactions to sensory stimuli, and its control of movements. They offer an accountof perception as the combination of prediction and observation: the brain builds internal modelsthat describe what should happen and then combines this prediction with reports from the sensorysystem to form a belief. Considering the brain's control of movements, and variations despitebiomechanical similarities among old and young, healthy and unhealthy, and humans and other animals,Shadmehr and Mussa-Ivaldi review evidence suggesting that motor commands reflect an economicdecision made by our brain weighing reward and effort. This evidence also suggests that the brainprefers to receive a reward sooner than later, devaluing or discounting reward with the passage oftime; then as the value of the expected reward changes in the brain with the passing of time(because of development, disease, or evolution), the shape of our movements will also change. Theinternal models formed by the brain provide the brain with an essential survival skill: the abilityto predict based on past observations. The formal concepts presented by Shadmehr and Mussa-Ivaldioffer a way to describe how representations are formed, what structure they have, and how thetheoretical concepts can be tested.

Reza Shadmehr is Professor of Biomedical Engineering and Neuroscience at Johns Hopkins University and the author of The Computational Neurobiology of Reaching and Pointing (MIT Press, 2005). Sandro Mussa-Ivaldi is Professor of Physiology in the Medical School at Northwestern University, with joint appointments in Physical Medicine and Rehabilitation and Biomedical Engineering. He is also Founder and Director of the Robotics Laboratory at the Rehabilitation Institute of Chicago.