Parietal area BA7 integrates motor programs for reaching, grasping, and bimanual coordination.
Skillful interaction with the world requires that the brain uses a multitude of sensorimotor programs and subroutines, such as for reaching, grasping, and the coordination of the two body halves. However, it is unclear how these programs operate together. Networks for reaching, grasping, and bimanual coordination might converge in common brain areas. For example, Brodmann area 7 (BA7) is known to activate in disparate tasks involving the three types of movements separately. Here, we asked whether BA7 plays a key role in integrating coordinated reach-to-grasp movements for both arms together. To test this, we applied transcranial magnetic stimulation (TMS) to disrupt BA7 activity in the left and right hemispheres, while human participants performed a bimanual size-perturbation grasping task using the index and middle fingers of both hands to grasp a rectangular object whose orientation (and thus grasp-relevant width dimension) might or might not change. We found that TMS of the right BA7 during object perturbation disrupted the bimanual grasp and transport/coordination components, and TMS over the left BA7 disrupted unimanual grasps. These results show that right BA7 is causally involved in the integration of reach-to-grasp movements of the two arms.



Our manuscript describes a role of human Brodmann area 7 (BA7) in the integration of multiple visuomotor programs for reaching, grasping, and bimanual coordination. Our results are the first to suggest that right BA7 is critically involved in the coordination of reach-to-grasp movements of the two arms. The results complement previous reports of right-hemisphere lateralization for bimanual grasps.
Department of Psychology, University of Toronto Scarborough, Toronto, Ontario, Canada.|Centre for Vision Research, York University, Toronto, Ontario, Canada.
Ada
A
Le
Centre for Vision Research, York University, Toronto, Ontario, Canada.|Division of Neurology and Krembil Neuroscience Centre, Toronto Western Research Institute, University of Toronto, Toronto, Ontario, Canada.
Michael
M
Vesia
Centre for Vision Research, York University, Toronto, Ontario, Canada.
Xiaogang
X
Yan
Centre for Vision Research, York University, Toronto, Ontario, Canada.|Neuroscience Graduate Diploma Program and Departments of Psychology, Biology, and Kinesiology & Health Sciences, York University, Toronto, Ontario, Canada; and.|Canadian Action and Perception Network, Toronto, Ontario, Canada.
J Douglas
JD
Crawford
Department of Psychology, University of Toronto Scarborough, Toronto, Ontario, Canada; niemeier@utsc.utoronto.ca.|Centre for Vision Research, York University, Toronto, Ontario, Canada.
Matthias
M
Niemeier
D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D005260:Female; D007839:Functional Laterality; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008297:Male; D009068:Movement; D010296:Parietal Lobe / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
TMS; bimanual; coordination; grasping; reaching