From Tying Shoelaces to Understanding Neurological Disorders: New Research Offers a Fresh Perspective on Motor Learning - Rehabilitation Institute of Chicago

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RIC in the News

Published on July 11, 2016

From Tying Shoelaces to Understanding Neurological Disorders: New Research Offers a Fresh Perspective on Motor Learning

CHICAGO — (July 11, 2016) — Consider an everyday action such as tying shoelaces. It consists of discrete halts in movement between continuous elemental actions, such as making a loop, or tugging at the lace. As people repeat movements, these elemental actions are merged into “chunks.” A new study, led by researchers at the Rehabilitation Institute of Chicago (RIC), makes significant advances in explaining the phenomenon of movement chunking and has important implications for the early diagnosis, treatment and rehabilitation therapy for patients with neurological disorders.

The field of computational motor control focuses on how the brain ought to control movements, given its goals and resource constraints (i.e., how the brain ought to optimize the efficiency of movement). In this context, researchers have had difficulty explaining how people learn to transition from computationally simple (but inefficient) movements to those that are computationally demanding (but efficient). This study resolves the issue by demonstrating that chunking is the natural by-product of a physiologically clever strategy that minimizes learning costs.

The research, published today in Nature Communications, presents two main findings. First, it develops a theory to explain why chunking occurs. By measuring how the nervous system in monkeys produces movement sequences over several days of practice, the authors found empirical evidence that chunks occur because of a tradeoff between efficiency and computational cost. On the one hand, the nervous system aims to produce movements as efficiently as possible. On the other, there is a computational cost to calculating efficient trajectories. Chunks are the sweet spot between these goals.

Second, the study demonstrates that there are certain stages during the learning of complex movements at which it is optimally cost-effective to merge small chunks. The data show that monkeys are indeed cost-effective learners whose nervous system decides when to merge chunks in an intelligent way. Specifically, the movement sequence is divided into chunks, optimizing for efficiency within chunks, and then merging chunks only when further gains in efficiency are required.

“By framing chunking as an economic tradeoff in the motor system, it opens up a broad range of questions regarding how the brain controls movements,” said Pavan Ramkumar, PhD, study lead author and RIC research associate. “For instance, other recent studies have reported evidence for the representation of chunks in patterns of neural circuit activity. These ideas should be re-examined in light of computational theories to understand whether neurons are coding movement states, control signals, computational budgets or efficiency goals.”

The research also has significant implications for the millions of people in the United States who suffer from neurological disorders.

“Ordinary movement chunking is severely disrupted in neurological disorders such as Parkinson’s disease, Huntington’s disease, and stroke, making the understanding of chunking crucial for rehabilitation and treatment,” said Konrad Kording, PhD, the study’s senior author, research scientist and head of the Economics of Movement Lab at RIC. “Framing chunking as an economic tradeoff offers a fresh perspective on motor learning and its disorders. Any rehabilitation approach can benefit from this insight.”

As an example, the irregular nature of movements post-stroke may be attributed to lower computational budgets for motor learning, and the inefficient movements seen in stroke may thus be adaptive to this budget.

In addition to Drs. Ramkumar and Kording, who have appointments at both RIC and the Department of Physical Medicine and Rehabilitation at Northwestern University, additional study co-authors include Daniel E. Acuna (Rehabilitation Institute of Chicago, Department of Physical Medicine and Rehabilitation, Northwestern University, and School of Information Studies, Syracuse University), Max Berniker (Department of Mechanical and Industrial Engineering, University of Illinois at Chicago), Scott T. Grafton (Department of Psychological and Brain Sciences, University of California, Santa Barbara), and Robert S. Turner (Department of Neurobiology and Systems Neurosciences Institute, University of Pittsburgh). The study’s experiments with monkeys were performed in Robert Turner’s lab at the University of Pittsburgh.

About the Rehabilitation Institute of Chicago (RIC)

The Rehabilitation Institute of Chicago (RIC) is the nation’s leading provider of comprehensive physical medicine and rehabilitation care to patients from around the world. Founded in 1953, RIC has been designated the “No. 1 Rehabilitation Hospital in America” by U.S. News & World Report every year since 1991. RIC sets the standard of care in the post-acute market through its innovative applied research and discovery programs, particularly in the areas of neuroscience, bionic medicine, musculoskeletal medicine and technology transfer. The Shirley Ryan AbilityLab — RIC’s new, state-of-the-art research hospital, will open in early 2017. For more information, go to

Media inquiries can be directed to Megan Washburn.