Donders Institute for Brain, Cognition and Behaviour
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Thesis defense Katrin Sutter (Donders Series 610)

23 June 2023

Promotor: Prof. dr. W.P. Medendorp
Co-promotors: Dr. L. Oostwoud Wijdenes and Dr. R.J. van Beers

Motor planning, control and learning in health and disease

A simple movement, like pushing the door open, requires complex control. Movement control entails a cascade of processes from movement planning to motor learning, and dealing with noise arising at different levels. This thesis sought to unravel how variability and motor learning shape reaching movements in health and disease.

To this aim we studied whether there is a tradeoff between movement planning time and movement precision. We observed a sizeable reduction of initial movement variability with increasing movement preparation time. Furthermore, we tested the hypothesis that repeating a well-practiced movement leads to a reduction of movement variability. Our findings show that, with repetition, movements are not only initiated earlier but their variability is reduced across the entire movement trajectory.

Finally, we investigated how an impairment of declarative memory affects the dynamics of motor learning. We measured Alzheimer’s disease patients and healthy age-matched controls in a reaching task with force-field learning. The time course of the motor learning was modeled by fitting a hierarchical Bayesian two-state model. Our results demonstrate that impairment of declarative memory leads to lower overall motor learning and pinpoints that this is due to faster forgetting of the fast motor learning process.

The results of the present thesis contribute to the understanding of reach planning, control, and adaptation in health and disease. There are numerous follow-up questions that require further study. These studies should not only address the neurocomputational correlates, but should also come up with paradigms that can translate the findings to rehabilitation practice and other applications.