Parietal area BA7 integrates motor programs for reaching, grasping, and bimanual coordination

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Neuroscience

Background:

• Coordinated movements, like reaching and grasping, rely on complex sensorimotor programs.
• The brain's integration of these programs, especially for bimanual tasks, remains poorly understood.
• Brodmann area 7 (BA7) is implicated in individual reaching, grasping, and bimanual coordination tasks.

Purpose of the Study:

• To investigate the causal role of Brodmann area 7 (BA7) in integrating bimanual reach-to-grasp movements.
• To determine if BA7 contributes to the coordination of movements involving both arms simultaneously.

Main Methods:

• Transcranial magnetic stimulation (TMS) was used to temporarily disrupt activity in the left and right BA7.
• Participants performed a bimanual size-perturbation grasping task involving a rectangular object.
• Object orientation was manipulated to alter the grasp-relevant width dimension.

Main Results:

• Disruption of the right BA7 by TMS impaired bimanual grasp and transport/coordination during object perturbation.
• Disruption of the left BA7 by TMS specifically affected unimanual grasp performance.
• These findings indicate a causal role for right BA7 in integrating bilateral reach-to-grasp actions.

Conclusions:

• Right BA7 is causally involved in the integration of reach-to-grasp movements for both arms.
• Left BA7 plays a role in unimanual grasp control.
• The study highlights hemispheric specialization within BA7 for sensorimotor integration and coordination.