High-fidelity musculoskeletal modeling reveals that motor planning variability contributes to the speed-accuracy tradeoff
Abstract
A long-standing challenge in motor neuroscience is to understand the relationship between movement speed and accuracy, known as the speed-accuracy tradeoff. Here, we introduce a biomechanically realistic computational model of three-dimensional upper extremity movements that reproduces well-known features of reaching movements. This model revealed that the speed-accuracy tradeoff, as described by Fitts’ law, emerges even without the presence of motor noise, which is commonly believed to underlie the speed-accuracy tradeoff. Next, we analyzed motor cortical neural activity from monkeys reaching to targets of different sizes. We found that the contribution of preparatory neural activity to movement duration (MD) variability is greater for smaller targets than larger targets, and that movements to smaller targets exhibit less variability in population-level preparatory activity, but greater MD variability. These results propose a new theory underlying the speed-accuracy tradeoff: Fitts’ law emerges from greater task demands constraining the optimization landscape in a fashion that reduces the number of ‘good’ control solutions (i.e., faster reaches). Thus, contrary to current beliefs, the speed-accuracy tradeoff could be a consequence of motor planning variability and not exclusively signal-dependent noise.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Dec 16, 2020
- Source ID
- 10.7554/elife.57021
Entities
People
- Krishna Shenoy
- Mazen Al Borno
- Saurabh Vyas
- Scott L. Delp
Organizations
- Defense Advanced Research Projects Agency
- Howard Hughes Medical Institute
- National Institute of Mental Health
- National Institute of Neurological Disorders and Stroke
- National Institutes of Health
- National Science Foundation
- Simons Foundation
- Stanford University
- University of Colorado Denver