Motor planning flexibly optimizes performance under uncertainty about task goals.

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Psychology

Background:

• The brain must select appropriate movements from multiple potential goals in complex environments.
• Previous theories proposed parallel preparation of multiple motor plans, evidenced by intermediate movements between competing goals.
• Intermediate movements were often interpreted as unintentional averaging of parallel motor plans.

Purpose of the Study:

• To investigate whether intermediate movements are unintentional averages or deliberate choices to optimize performance.
• To test the hypothesis that intermediate movements are generated when they offer a performance benefit over random selection.

Main Methods:

• Participants performed a task involving competing movement goals.
• Movement speed was manipulated to vary the potential benefit of executing an intermediate movement.
• The relationship between movement speed, intermediate movement generation, and task performance was analyzed.

Main Results:

• Intermediate movements were produced significantly only at slower movement speeds.
• Slower speeds were associated with measurable performance improvements when intermediate movements were executed.
• No intermediate movements were observed at faster speeds where they did not enhance performance.

Conclusions:

• Findings support normative theories suggesting the motor system selects a single, optimized motor plan for uncertain goals.
• Intermediate movements are not necessarily an artifact of parallel plan averaging but can be a deliberate strategy.
• Motor control is flexible and goal-directed, adapting to optimize performance under uncertainty.