Wide-field retinotopy reveals a new visuotopic cluster in macaque posterior parietal cortex

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.

Population receptive fields in nonhuman primates from whole-brain fMRI and large-scale neurophysiology in visual cortex

“…For both monkeys (M1 and M2), we found robust retinotopic information in occipital, temporal, and parietal cortex ( Figure 2 ). pRFs in all these areas were in the contralateral visual field and retinotopic maps were consistent with previous reports ( Figure 2B ), some of which were more extensive ( Arcaro et al, 2011 ; Arcaro and Livingstone, 2017 ; Brewer et al, 2002 ; Janssens et al, 2014 ; Kolster et al, 2014 ; Rima et al, 2020 ; Zhu and Vanduffel, 2019 ). Weaker and sparser retinotopic information was also observed in the frontal cortex, for example, around the arcuate sulcus (area 8, including the frontal eye fields [FEF]) and in the ventrolateral prefrontal cortex (VLPFC).…”

Population receptive fields in non-human primates from whole-brain fMRI and large-scale neurophysiology in visual cortex

“…For both monkeys (M1 & M2), we found robust retinotopic information in occipital, temporal, and parietal cortex (Figure 2). PRFs in all these areas were in the contralateral visual field and retinotopic maps were consistent with previous reports (Figure 2B), some of which were more extensive (Arcaro et al, 2011; Arcaro and Livingstone, 2017; Brewer et al, 2002; Janssens et al, 2014; Kolster et al, 2014; Rima et al, 2020; Zhu and Vanduffel, 2019). Weaker and sparser retinotopic information was also observed in the frontal cortex, e.g.…”

Myelin densities in retinotopically defined dorsal visual areas of the macaque

“…Our analyses are limited to the cortex representing the central 12° of eccentricity. Large-field retinotopic mapping is still required to better understand the functional organization of visual cortex representing higher eccentricities (Gamberini et al 2015 ; Hadjidimitrakis et al 2019 ; Rima et al 2020 ). Future studies combining ultra-high-resolution functional imaging and MR-based histology (Eickhoff et al 2005 ; Xu et al 2019 ; Assaf 2019 ) in the same subjects will also provide a more comprehensive picture of mesoscale cortical variations across layers, ultimately leading to a comprehensive parcellation of primate visual cortex.…”