Early coding of reaching: frontal and parietal association connections of parieto-occipital cortex.
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.
Caminiti
R
R
Istituto di Fisiologia umana, Università di Roma La Sapienza, Rome, Italy. caminitir@axrma.uniroma1.it
Genovesio
A
A
Marconi
B
B
Mayer
A B
AB
Onorati
P
P
Ferraina
S
S
Mitsuda
T
T
Giannetti
S
S
Squatrito
S
S
Maioli
M G
MG
Molinari
M
M
D000818:Animals; D001931:Brain Mapping; D005625:Frontal Lobe / Q000033:anatomy & histology* / Q000502:physiology*; D018737:Hand Strength / Q000502:physiology*; D006651:Histocytochemistry; D008253:Macaca mulatta; D009044:Motor Cortex / Q000502:physiology; D009068:Movement / Q000502:physiology; D009434:Neural Pathways / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology; D009778:Occipital Lobe / Q000033:anatomy & histology* / Q000166:cytology / Q000502:physiology*; D009801:Oculomotor Muscles / Q000294:innervation / Q000502:physiology; D010296:Parietal Lobe / Q000033:anatomy & histology* / Q000166:cytology / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*