Mixed Body/Hand Reference Frame for Reaching in 3D Space in Macaque Parietal Area PEc

Area of Science:

• Neuroscience
• Motor Control
• Computational Neuroscience

Background:

• The posterior parietal cortex (PPC) is crucial for transforming sensory information into motor commands.
• Different medial PPC areas represent reaching targets in distinct coordinate frames (e.g., hand-centered in PE, eye/body-centered in V6A).

Purpose of the Study:

• To investigate the coordinate frame used by neurons in area PEc, located between V6A and PE in the medial PPC.
• To determine how PEc neurons encode target locations during reaching movements.

Main Methods:

• Electrophysiological recordings from 104 PEc neurons in three macaque monkeys.
• A reaching task in darkness with targets at various depths and directions.
• Starting hand positions varied (near trunk vs. far).

Main Results:

• Most PEc neurons encoded reaching targets in a mixed body/hand-centered reference frame.
• The influence of hand position on target encoding was significant but less pronounced than in area PE.
• This suggests a gradual transformation of coordinate frames within the medial PPC.

Conclusions:

• Area PEc acts as an intermediate processing stage in the visual-to-motor transformation pathway.
• PEc contributes to the integration of body and hand information for reaching.
• Findings elucidate the functional organization of the dorsomedial PPC in sensorimotor control.