Abstract
We investigated the visuotopic organization of macaque posterior parietal cortex (PPC) by combining functional imaging (fMRI) and wide-field retinotopic mapping in two macaque monkeys. Whole brain blood-oxygen-level-dependent (BOLD) signal was recorded while monkeys maintained central fixation during the presentation of large rotating wedges and expending/contracting annulus of a “shaking” fruit basket, designed to maximize the recruitment of PPC neurons. Results of the surface-based population receptive field (pRF) analysis reveal a new cluster of four visuotopic areas at the confluence of the parieto-occipital and intra-parietal sulci, in a location previously defined histologically and anatomically as the posterior intra-parietal (PIP) region. This PIP cluster groups together two recently described areas (CIP1/2) laterally and two newly identified ones (PIP1/2) medially, whose foveal representations merge in the fundus of the intra-parietal sulcus. The cluster shares borders with other visuotopic areas: V3d posteriorly, V3A/DP laterally, V6/V6A medially and LIP anteriorly. Together, these results show that monkey PPC is endowed with a dense set of visuotopic areas, as its human counterpart. The fact that fMRI and wide-field stimulation allows a functional parsing of monkey PPC offers a new framework for studying functional homologies with human PPC.
Highlights
In primates, the posterior parietal cortex (PPC) constitutes the end stage of the dorsal visual pathway and as such, it is notably involved in visuospatial and visuomotor functions (Buneo and Andersen 2006; Freedman and Ibos 2018; Hadjidimitrakis et al 2019a, b)
Besides confirming the existence of CIP1 and CIP2, our results show that they form a visuotopic cluster with 2 additional previously unknown areas of the posterior intraparietal sulcus, PIP1 and PIP2
We have investigated the visuotopic organization of primate PPC with functional magnetic resonance imaging (fMRI) in 2 behaving macaque monkeys
Summary
The posterior parietal cortex (PPC) constitutes the end stage of the dorsal visual pathway and as such, it is notably involved in visuospatial and visuomotor functions (Buneo and Andersen 2006; Freedman and Ibos 2018; Hadjidimitrakis et al 2019a, b). Several visuotopic areas have been progressively unveiled in human PPC (Sereno et al 2001; Schluppeck et al 2005; Silver et al 2005; Swisher et al 2007; Konen and Kastner 2008), thanks to the development of functional magnetic resonance imaging (fMRI) techniques for non-invasive retinotopic mapping (Sereno et al 1995; Engel et al 1997). These studies have drawn the view of a dense. A recent study (HéjjaBrichard et al 2020) has shown this area to be sensitive to cyclopean stereomotion in macaque monkeys, with a potential human homolog being area POIPS described in (Georgieva et al 2009)
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