Complexity of central processing in simple and choice multilimb reaction-time tasks.

Area of Science:

• Motor control
• Human movement science
• Cognitive neuroscience

Background:

• The motor system defaults to coupled limb movements.
• Decoupling limbs requires selection and inhibition/facilitation processes.
• Understanding recruitment vs. selection complexity is crucial for motor control research.

Purpose of the Study:

• To investigate the relative contributions of recruitment and selection processes to motor processing complexity.
• To quantify the impact of different limb coordination modes on reaction time and errors.
• To develop a model explaining motor system coupling and decoupling dynamics.

Main Methods:

• A novel multilimb reaction-time task (MUL-RT) was developed.
• Thirty-six adults performed 15 coordination modes involving varying limb recruitment.
• Simple and normalized reaction times (RTs) were analyzed to assess recruitment and selection, respectively.

Main Results:

• Limb selection complexity varied: diagonal > ipsilateral > homologous.
• Upper limb selection was less complex than lower limb selection.
• Recruitment complexity decreased with more limbs, while selection complexity varied by coordination mode.

Conclusions:

• Motor control involves a balance between limb recruitment and selection processes.
• The complexity of motor tasks is influenced by the number of limbs and their coordination patterns.
• The 'recruitment principle' dominates simple RT, while both 'recruitment' and 'selection principles' contribute to choice RT complexity.