[Abstract Title]. - Society for Neuroscience

Fondazione del Monte di Bologna e Ravenna
FP6-IST-027574-MATHESIS
Title: Cortical connections of macaque parietal area PEc
Authors: S. BAKOLA, M. GAMBERINI, L. PASSARELLI, P. FATTORI, *C. GALLETTI;
Dept. Human & Gen. Physiol., Univ. Bologna, Bologna, Italy
Abstract: The present report examines the connectivity patterns of area PEc, a cortical area
located in the caudal part of the posterior parietal lobe. Retrograde fluorescent tracers were
injected or placed directly as crystals on the exposed cortical convexity of six cynomolgus
monkeys (Macaca fascicularis) within the cytoarchitectonic limits of PEc. We observed
ipsilateral cortical projections from visuomotor and somatosensory areas as well as from motor
areas with somatotopic organization. The heaviest projections were from the neighboring areas
of the parietal lobe. Labeled cells were in area PE, immediately rostral to the injection sites, in
areas MIP and PEip in the medial intraparietal bank, and in area V6A in the anterior bank of the
parieto-occipital sulcus. Dense input arose also from area PEci at the caudal tip of the cingulate
sulcus, whereas primary and secondary somatosensory areas provided weaker labeling. In
addition, modest numbers of labeled cells were noted in areas PFG, on the parietal convexity,
and in the parietal opercular area PGop. In the frontal lobe, labeling originated mostly in the
dorsal part of area F2, around the superior precentral dimple, and to a lesser extent in medial area
F3 and primary motor cortex. Further projections arose from the mesial cortical surface of the
hemisphere, in and around the cingulate sulcus, mainly from its posterior part. There was no
significant labeling in early visual, superior temporal and prefrontal areas or in the known
oculomotor centers. An anteroposterior gradient was evident so that more posterior injection
sites were targeted by visuomotor areas and more anterior ones by somatosensory-related areas.
Our findings are in agreement with the described physiological properties of PEc neurons
(visual, somatosensory, and bimodal neurons; Breveglieri et al, 2006; 2008), but emphasize a
skeletomotor function for this area. We suggest that PEc relays proprioceptive, rather than visual,
information about the position of body parts that can be used by motor cortices with direct output
to the spinal cord. The anatomical link from PEc to premotor areas that host a representation of
the upper and lower limbs, but not the hands or face, presumably implies a role in locomotion
and coordinated body movement in the environment. Visual information in PEc is likely used to
integrate somatosensory information for the control of body movements.
Disclosures: S. Bakola, None; C. Galletti, None; M. Gamberini, None; L. Passarelli, None; P.
Fattori, None.
Poster
262. Visually-Guided Reaching II