State space analysis of timing: exploiting task redundancy to reduce sensitivity to timing

Area of Science:

• Motor control
• Human movement science
• Cognitive neuroscience

Background:

• Accurate timing of central nervous system commands is crucial for skilled motor performance.
• Hand trajectory shaping and temporal accuracy are key factors in achieving task success.

Purpose of the Study:

• To develop a novel analysis quantifying the contributions of timing accuracy and hand trajectory shaping to performance in a target-oriented throwing task.
• To investigate how learners improve timing accuracy and trajectory shaping with practice.
• To differentiate the learning strategies of skilled versus unskilled performers.

Main Methods:

• Utilized a virtual environment for a target-oriented throwing task.
• Developed a new analytical method to measure timing accuracy and trajectory shaping.
• Compared performance improvements in subjects with 6 days versus 15 days of practice.

Main Results:

• Performance is determined by projectile position and velocity at release, with a 'solution manifold' allowing for error correction.
• Learners improved both timing accuracy (around 10 ms) and trajectory alignment with practice.
• Skilled performers demonstrated superior timing accuracy and utilized both timing and trajectory optimization.
• Extended practice led to further trajectory shaping, while timing accuracy plateaued around 9 ms.

Conclusions:

• Skilled performers initially maximize timing accuracy and subsequently optimize trajectory shaping.
• Trajectory optimization is essential for compensating for the inherent limitations of motor timing accuracy.
• This study provides insights into the dual strategies underlying motor skill acquisition and refinement.