Journal ArticleDOI
Signal-dependent noise determines motor planning
Chris Harris,Daniel M. Wolpert +1 more
TLDR
This theory provides a simple and powerful unifying perspective for both eye and arm movement control and accurately predicts the trajectories of both saccades and arm movements and the speed–accuracy trade-off described by Fitt's law.Abstract:
When we make saccadic eye movements or goal-directed arm movements, there is an infinite number of possible trajectories that the eye or arm could take to reach the target1,2. However, humans show highly stereotyped trajectories in which velocity profiles of both the eye and hand are smooth and symmetric for brief movements3,4. Here we present a unifying theory of eye and arm movements based on the single physiological assumption that the neural control signals are corrupted by noise whose variance increases with the size of the control signal. We propose that in the presence of such signal-dependent noise, the shape of a trajectory is selected to minimize the variance of the final eye or arm position. This minimum-variance theory accurately predicts the trajectories of both saccades and arm movements and the speed–accuracy trade-off described by Fitt's law5. These profiles are robust to changes in the dynamics of the eye or arm, as found empirically6,7. Moreover, the relation between path curvature and hand velocity during drawing movements reproduces the empirical ‘two-thirds power law’8,9. This theory provides a simple and powerful unifying perspective for both eye and arm movement control.read more
Citations
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Journal ArticleDOI
Effect of fatigue on force fluctuations in knee extensors in young adults
TL;DR: NMAE, NSAE and NPAE increased significantly post-fatigue, together with a shift towards higher frequency (MnPF and MdPF) components, indicating that the set-up was sensitive enough to detect the decreased force accuracy and steadiness of the musculature after fatigue.
Journal ArticleDOI
Adaptation of motor behavior to preserve task success in the presence of muscle fatigue.
TL;DR: An optimal control model was used to determine how fatigue-induced changes in variables such as noise in motor commands, muscle contraction and relaxation times, and the gain between neural activation and muscle force may contribute to changes in Fitts's law with fatigue.
Journal ArticleDOI
Cortisol-induced effects on human cortical excitability.
Paolo Milani,Pietro Piu,Traian Popa,Raimondo della Volpe,Marco Bonifazi,Alessandro Rossi,Riccardo Mazzocchio +6 more
TL;DR: It is suggested that high circulating levels of cortisol rapidly increase corticospinal excitability and reduce gamma aminobutyric acid activity, as measured by short-intracortical inhibition, in humans, compatible with a nongenomic mechanism.
Journal ArticleDOI
Emulsification of Silicone Oil and Eye Movements
Yau Kei Chan,Chiu-On Ng,Paul C. Knox,Michael Joseph Garvey,Rachel Williams,David Wong,David Wong +6 more
TL;DR: The results showed that it was the shear viscosity that determined the relative velocity between the oil and the wall of the vitreous cavity, and thus the propensity to emulsify.
Journal ArticleDOI
Individual Differences in Motor Noise and Adaptation Rate Are Optimally Related.
Rick van der Vliet,Maarten A. Frens,Maarten A. Frens,Linda de Vreede,Zeb D. Jonker,Gerard M. Ribbers,Ruud W. Selles,Jos N. van der Geest,Opher Donchin,Opher Donchin +9 more
TL;DR: The results of this visuomotor adaptation experiment suggest that motor adaptation is tuned to approximate optimal learning, consistent with the “optimal control” framework that has been used to explain motor control.
References
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Journal ArticleDOI
The information capacity of the human motor system in controlling the amplitude of movement.
TL;DR: The motor system in the present case is defined as including the visual and proprioceptive feedback loops that permit S to monitor his own activity, and the information capacity of the motor system is specified by its ability to produce consistently one class of movement from among several alternative movement classes.
Journal ArticleDOI
The coordination of arm movements: an experimentally confirmed mathematical model.
Tamar Flash,Neville Hogan +1 more
TL;DR: A mathematical model is formulated which is shown to predict both the qualitative features and the quantitative details observed experimentally in planar, multijoint arm movements, and is successful only when formulated in terms of the motion of the hand in extracorporal space.
Journal ArticleDOI
An Internal Model for Sensorimotor Integration
TL;DR: A sensorimotor integration task was investigated in which participants estimated the location of one of their hands at the end of movements made in the dark and under externally imposed forces, providing direct support for the existence of an internal model.
Journal ArticleDOI
Adaptive representation of dynamics during learning of a motor task
TL;DR: The investigation of how the CNS learns to control movements in different dynamical conditions, and how this learned behavior is represented, suggests that the elements of the adaptive process represent dynamics of a motor task in terms of the intrinsic coordinate system of the sensors and actuators.
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Optimal feedback control as a theory of motor coordination.
The coordination of arm movements: an experimentally confirmed mathematical model.
Tamar Flash,Neville Hogan +1 more