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LABORATORY OF FUNCTIONAL NEUROANATOMY OF THE VISUO-MOTOR SYSTEMS
Cortical connections of visual area V6
Area V6 is a cortical visual area (Galletti et al., 1996) which is retinotopically organized (Galletti et al., 1999a). We made WGA-HRP tracer injections in central and peripheral visual field representation of area V6 (Galletti et al., 2001) (see Fig. 1). The results showed that V6 is directly connected with V1, the occipital extrastriate areas, and the parietal areas of the dorsal visual stream (Fig. 2). Central and peripheral representations of V6 showed connections with the same cortical areas, but we observed that in retinotopically organized areas the connections were with different regions of the areas according to their retinotopic organization (Fig. 3).
Cortical connections of area V6A
Injections made in the frontal lobe (in the dorsal premotor areas F2 and F7 according to Matelli et al., 1991) showed afferences from area V6A (Matelli et al., 1998) (Fig. 4). We are currently studying the cortical connections of area V6A by injecting neuronal tracers directly into area V6A. We start analyzing the cortical connections of the dorsal sector of V6A (Gamberini et al., 2009) by injecting neuronal retrograde tracers within the limits of the cytoarchitectonically recognized area V6Ad (Fig. 5). V6Ad is connected with areas of the caudal superior and inferior parietal lobules, the intraparietal sulcus, the frontal cortex, and the cortex of the mesial wall of the hemisphere. The strongest connections were with areas MIP and LIP in the intraparietal sulcus, with architectural fields PG in the inferior parietal lobule, F2 (the dorsal premotor area) in the frontal cortex, and PGm in the mesial wall of the hemisphere (Fig. 6). In agreement with functional data, the strong connections with areas where arm-reaching activity is represented suggest that V6Ad is part of a parietofrontal circuit involved in the control of prehension, and connections with AIP specifically support an involvement in the control of grasping. Connections with areas LIP and Opt are likely related to the oculomotor activities observed in V6Ad.
Cytoarchitectonic subdivision of the anterior bank of parieto-occipital sulcus
The functionally defined areas V6 and V6A (Galletti et al., 1999a; Galletti et al., 1999b), located on the anterior bank of the parieto-occipital sulcus (APO), were considered part of areas 18 and 19 of Brodmann (Brodmann, 1909). We have recently made a cytoarchitectonic study of this part of the macaque brain (Luppino et al., 2005) using different planes of cutting and different staining. The ventral part of APO (V6) shows a typical occipital cytoarchitectonic pattern. The dorsal part of APO (V6A) is subdivided in two sectors (named V6Av and V6Ad) and shows a cytoarchitectonic parietal pattern (Fig. 7).
Cytoarchitectonically defined area PEc
Area PEc was originally defined by Pandya and Seltzer (Pandya & Seltzer, 1982) on the basis of cytoarchitectonic criteria. These authors located area PEc in the caudal aspect of the superior parietal lobule. We have recently reanalyzed the cytoarchitectonic pattern of this region of the brain (Luppino et al., 2005; Breveglieri et al., 2006) (see Fig. 8): area PEc has a typical parietal pattern with large layer III with a size gradient and hight number of large pyramids in layer V.
Breveglieri, R., Galletti, C., Gamberini, M., Passarelli, L. & Fattori, P. (2006) Somatosensory cells in area PEc of macaque posterior parietal cortex. J Neurosci, 26, 3679-3684.
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Gamberini, M., Passarelli, L., Fattori, P., Zucchelli, M., Bakola, S., Luppino, G. & Galletti, C. (2009) Cortical connections of the visuomotor parietooccipital area V6A of the macaque monkey. J Comp Neurol, 513 (6), 622-642.
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