Neurophysiology of prehension. III. Representation of object features in posterior parietal cortex of the macaque monkey.


Journal Article

Neurons in posterior parietal cortex (PPC) may serve both proprioceptive and exteroceptive functions during prehension, signaling hand actions and object properties. To assess these roles, we used digital video recordings to analyze responses of 83 hand-manipulation neurons in area 5 as monkeys grasped and lifted objects that differed in shape (round and rectangular), size (large and small spheres), and location (identical rectangular blocks placed lateral and medial to the shoulder). The task contained seven stages -- approach, contact, grasp, lift, hold, lower, relax -- plus a pretrial interval. The four test objects evoked similar spike trains and mean rate profiles that rose significantly above baseline from approach through lift, with peak activity at contact. Although representation by the spike train of specific hand actions was stronger than distinctions between grasped objects, 34% of these neurons showed statistically significant effects of object properties or hand postures on firing rates. Somatosensory input from the hand played an important role as firing rates diverged most prominently on contact as grasp was secured. The small sphere -- grasped with the most flexed hand posture -- evoked the highest firing rates in 43% of the population. Twenty-one percent distinguished spheres that differed in size and weight, and 14% discriminated spheres from rectangular blocks. Location in the workspace modulated response amplitude as objects placed across the midline evoked higher firing rates than positions lateral to the shoulder. We conclude that area 5 neurons, like those in area AIP, integrate object features, hand actions, and grasp postures during prehension.

Full Text

Cited Authors

  • Gardner, EP; Babu, KS; Ghosh, S; Sherwood, A; Chen, J

Published Date

  • December 2007

Published In

Volume / Issue

  • 98 / 6

Start / End Page

  • 3708 - 3730

PubMed ID

  • 17942625

Pubmed Central ID

  • 17942625

Electronic International Standard Serial Number (EISSN)

  • 1522-1598

International Standard Serial Number (ISSN)

  • 0022-3077

Digital Object Identifier (DOI)

  • 10.1152/jn.00609.2007


  • eng