Movement speed is biased by prior experience.

Area of Science:

• Motor control
• Human movement science
• Neuroplasticity

Background:

• Current models of motor control often focus on balancing movement speed costs against goal achievement rewards.
• The role of pre-existing, modifiable internal representations of preferred movement speed is less understood.

Purpose of the Study:

• To investigate the influence of a practiced preferred movement speed on motor system's speed selection.
• To determine if prolonged practice can alter the internal representation of movement speed.

Main Methods:

• Participants performed time-constrained 25-cm reaching movements under various speed requirements (300-900 ms).
• Three days of training focused on executing movements at either the slowest (900 ms) or fastest (300 ms) speed.
• Movement speed, amplitude errors, and directional errors were assessed before and after training.

Main Results:

• Post-training movements under all time constraints showed a bias toward the practiced speed.
• Trial-to-trial speed variability decreased significantly for the trained movement.
• Reduced speed variability correlated with improved movement amplitude accuracy, particularly for fast training, and showed generalization to new directions.

Conclusions:

• A stable yet adaptable internal prior for preferred movement speed exists and influences motor execution.
• Use-dependent plasticity modifies this internal speed representation, impacting movement selection and variability.
• Practice-induced changes in speed preference can enhance movement accuracy and generalize across different contexts.