The human homologue of macaque area V6A

Abstract

In macaque monkeys, V6A is a visuomotor area located in the anterior bank of the POs, dorsal and anterior to retinotopically-organized extrastriate area V6 (Galletti et al 1996). Unlike V6, V6A represents both contra- and ipsilateral visual fields and is broadly retinotopically organized (Galletti et al 1999b). The contralateral lower visual field is overrepresented in V6A. The central 20°–30° of the visual field are mainly represented dorsally (V6Ad) and the periphery ventrally (V6Av), at the border with V6. Both sectors of area V6A contain arm movement-related cells, active during spatially-directed reaching movements (Gamberini et al., 2011). In humans, we previously mapped the retinotopic organization of area V6 (Pitzalis et al., 2006). Here, using phase-encoded fMRI, cortical surface-based analysis and wide-field retinotopic mapping, we define a new cortical region that borders V6 anteriorly and shows a clear over-representation of the contralateral lower visual field and of the periphery. As with macaque V6A, the eccentricity increases moving ventrally within the area. The new region contains a non-mirror-image representation of the visual field. Functional mapping reveals that, as in macaque V6A, the new region, but not the nearby area V6, responds during finger pointing and reaching movements. Based on similarity in position, retinotopic properties, functional organization and relationship with the neighbouring extrastriate visual areas, we propose that the new cortical region is the human homologue of macaque area V6A.

Multiple Aspects of Neural Activity during Reaching Preparation in the Medial Posterior Parietal Area V6A

“…This view is in agreement with what was found in human PPC, where more posterior regions (including the putative homologue of area V6A; see Pitzalis et al, 2013) were less activated during reaching preparation than more anterior areas (including the putative homologue of PRR; see Galati et al, 2011). A similar gradient of selectivity seems to exist in monkey Copyright of Journal of Cognitive Neuroscience is the property of MIT Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission.…”

Effect of different directions of attentional shift on inhibition of return in three-dimensional space

“…Electrophysiological and tract tracting studies in monkeys have suggested a role of the visual area 6 (V6) complex as a potential candidate region in which information from the ventral and dorsal streams is integrated (Breveglieri, Galletti, Gamberini, Passarelli, & Fattori, 2006;Breveglieri, Kutz, Fattori, Gamberini, & Galletti, 2002;Galletti, Fattori, Kutz, & Battaglini, 1997). In the human brain, the POJ is a putative homologue of the monkey V6 complex (Galletti, Gamberini, Kutz, Baldinotti, & Fattori, 2005;Galletti, Kutz, Gamberini, Breveglieri, & Fattori, 2003;Pitzalis et al, 2013). Therefore, stimuli that unexpectedly approach observers instantaneously demand a shift of attention toward them in order to secure survival.…”

Beyond the “Bereitschaftspotential”: Action preparation behind cognitive functions

“…The more anterior activity observed for grasping a cup, possibly related to area AIP, would be explained by a visuo-motor gradient along the PPC in the posterior-anterior direction, with posteriorreaching regions dominated by visual/attentional signals, and anterior-grasping ones under the control of the effectors that will be used in the following action (e.g. Filimon et al, 2009;45 Filimon, 2010;Galati et al, 2011;Pitzalis et al, 2013;Tosoni et al, 2014). According to this gradient, spatial specificity decreases and action specificity increases when gradually moving from posterior to anterior regions.…”