Single Units in the Posterior Parietal Cortex Encode Patterns of Bimanual Coordination.

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Science

Background:

• Bimanual coordination is essential for many daily activities, yet the neural mechanisms underlying its planning remain unclear.
• Neurons in the parietal reach region (PRR) of the posterior parietal cortex (PPC) show activity during unilateral arm movements, suggesting a role in coordination.
• Understanding the early stages of movement planning is crucial for deciphering complex motor behaviors.

Purpose of the Study:

• To investigate the role of PRR neurons in planning unilateral versus bimanual arm movements.
• To determine whether PRR activity reflects sensory responses or motor plans during arm movements.
• To elucidate the neural basis of bimanual coordination planning within the PPC.

Main Methods:

• Electrophysiological recordings of single neurons in the PRR during unilateral and bimanual reaching tasks.
• Analysis of neuronal activity preceding and during arm movements.
• Comparison of neural responses to visual targets and motor commands.

Main Results:

• Activity preceding ipsilateral arm movements was primarily a sensory response to visual targets.
• Activity preceding contralateral arm movements reflected a combination of motor planning and sensory input.
• Approximately half of the recorded PRR neurons discriminated between different bimanual movement patterns, despite not coding ipsilateral movements.

Conclusions:

• PRR neurons play a critical role in representing bimanual reach plans.
• Bimanual coordination planning originates within the PPC's sensory-to-motor processing stream, preceding motor cortex involvement.
• These findings offer direct evidence for the PPC's contribution to complex, coordinated movements involving multiple limbs.