title: Neurophysiology of prehension. II. Response diversity in primary somatosensory (S-I) and motor (M-I) cortices.
abstract: Prehension responses of 76 neurons in primary somatosensory (S-I) and motor (M-I) cortices were analyzed in three macaques during performance of a grasp and lift task. Digital video recordings of hand kinematics synchronized to neuronal spike trains were compared with responses in posterior parietal areas 5 and AIP/7b (PPC) of the same monkeys during seven task stages: 1) approach, 2) contact, 3) grasp, 4) lift, 5) hold, 6) lower, and 7) relax. S-I and M-I firing patterns signaled particular hand actions, rather than overall task goals. S-I responses were more diverse than those in PPC, occurred later in time, and focused primarily on grasping. Sixty-three percent of S-I neurons fired at peak rates during contact and/or grasping. Lift, hold, and lowering excited fewer S-I cells. Only 8% of S-I cells fired at peak rates before contact, compared with 27% in PPC. M-I responses were also diverse, forming functional groups for hand preshaping, object acquisition, and grip force application. M-I activity began < or =500 ms before contact, coinciding with the earliest activity in PPC. Activation of specific muscle groups in the hand was paralleled by matching patterns of somatosensory feedback from S-I needed for efficient performance. These findings support hypotheses that predictive and planning components of prehension are represented in PPC and premotor cortex, whereas performance and feedback circuits dominate activity in M-I and S-I. Somatosensory feedback from the hand to S-I enables real-time adjustments of grasping by connections to M-I and updates future prehension plans through projections to PPC.
authors.affiliation: Department of Physiology and Neuroscience, New York University School of Medicine, 550 First Avenue, MSB 442, New York, NY 10016, USA. gardne01@endeavor.med.nyu.edu
authors.forename: Esther P
authors.initials: EP
authors.lastname: Gardner
authors.forename: Jin Y
authors.initials: JY
authors.lastname: Ro
authors.forename: K Srinivasa
authors.initials: KS
authors.lastname: Babu
authors.forename: Soumya
authors.initials: S
authors.lastname: Ghosh
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D003627:Data Interpretation, Statistical; D019054:Evoked Potentials, Motor / Q000502:physiology; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005246:Feedback / Q000502:physiology; D005260:Female; D006225:Hand / Q000502:physiology; D018737:Hand Strength / Q000502:physiology*; D008253:Macaca mulatta; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology; D010296:Parietal Lobe / Q000502:physiology; D011434:Proprioception / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology*; D014110:Touch / Q000502:physiology