Early coding of reaching: frontal and parietal association connections of parieto-occipital cortex

Eur J Neurosci. 1999 Sep;11(9):3339-45. doi: 10.1046/j.1460-9568.1999.00801.x.


The ipsilateral association connections of the cortex of the dorsal part of the rostral bank of the parieto-occipital sulcus and of the adjoining posterior part of the superior parietal lobule were studied by using different retrograde fluorescent tracers. Fluoro-Ruby, Fast blue and Diamidino yellow were injected into visual area V6A, and dorso-caudal (PMdc, F2) and dorso-rostral (PMdr, F7) premotor cortex, respectively. The parietal area of injection had been previously characterized physiologically in behaving monkeys, through a variety of oculomotor and visuomanual tasks. Area V6A is mainly linked by reciprocal projections to parietal areas 7m, MIP (medial intraparietal) and PEa, and, to a lesser extent, to frontal areas PMdr (rostral dorsal premotor cortex, F7) and PMdc (F2). All these areas project to that part of the dorsocaudal premotor cortex that has a direct access to primary motor cortex. V6A is also connected to area F5 and, to a lesser extent, to 7a, ventral (VIP) and lateral (LIP) intraparietal areas. This pattern of association connections may explain the presence of visually-related and eye-position signals in premotor cortex, as well as the influence of information concerning arm position and movement direction on V6A neural activity. Area V6A emerges as a potential 'early' node of the distributed network underlying visually-guided reaching. In this network, reciprocal association connections probably impose, through re-entrant signalling, a recursive property to the operations leading to the composition of eye and hand motor commands.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain Mapping
  • Frontal Lobe / anatomy & histology*
  • Frontal Lobe / physiology*
  • Hand Strength / physiology*
  • Histocytochemistry
  • Macaca mulatta
  • Motor Cortex / physiology
  • Movement / physiology
  • Neural Pathways / anatomy & histology
  • Neural Pathways / cytology
  • Neural Pathways / physiology
  • Occipital Lobe / anatomy & histology*
  • Occipital Lobe / cytology
  • Occipital Lobe / physiology*
  • Oculomotor Muscles / innervation
  • Oculomotor Muscles / physiology
  • Parietal Lobe / anatomy & histology*
  • Parietal Lobe / cytology
  • Parietal Lobe / physiology*
  • Space Perception / physiology*