Abstract
The cortical hierarchy of the human visual system has been shown to be organized around retinal spatial coordinates throughout much of low- and mid-level visual processing. These regions contain visual field maps (VFMs) that each follows the organization of the retina, with neighboring aspects of the visual field processed in neighboring cortical locations. On a larger, macrostructural scale, groups of such sensory cortical field maps (CFMs) in both the visual and auditory systems are organized into roughly circular cloverleaf clusters. CFMs within clusters tend to share properties such as receptive field distribution, cortical magnification, and processing specialization. Here we use fMRI and population receptive field (pRF) modeling to investigate the extent of VFM and cluster organization with an examination of higher-level visual processing in temporal cortex and compare these measurements to mid-level visual processing in dorsal occipital cortex. In human temporal cortex, the posterior superior temporal sulcus (pSTS) has been implicated in various neuroimaging studies as subserving higher-order vision, including face processing, biological motion perception, and multimodal audiovisual integration. In human dorsal occipital cortex, the transverse occipital sulcus (TOS) contains the V3A/B cluster, which comprises two VFMs subserving mid-level motion perception and visuospatial attention. For the first time, we present the organization of VFMs in pSTS in a cloverleaf cluster. This pSTS cluster contains four VFMs bilaterally: pSTS-1:4. We characterize these pSTS VFMs as relatively small at ∼125 mm2 with relatively large pRF sizes of ∼2–8° of visual angle across the central 10° of the visual field. V3A and V3B are ∼230 mm2 in surface area, with pRF sizes here similarly ∼1–8° of visual angle across the same region. In addition, cortical magnification measurements show that a larger extent of the pSTS VFM surface areas are devoted to the peripheral visual field than those in the V3A/B cluster. Reliability measurements of VFMs in pSTS and V3A/B reveal that these cloverleaf clusters are remarkably consistent and functionally differentiable. Our findings add to the growing number of measurements of widespread sensory CFMs organized into cloverleaf clusters, indicating that CFMs and cloverleaf clusters may both be fundamental organizing principles in cortical sensory processing.
Highlights
In many mammals, including humans, low and mid-level sensory cortex contains multiple, functionally specialized cortical field maps (CFMs), in which neurons whose sensory receptive fields are positioned next to one another in sensory feature space are located next to one another in cortex
We found that V3A and V3B exhibited increasing population receptive field (pRF) sizes as a function of eccentricity (Figures 8A,B); this is similar to the V1-hV4 visual field maps (VFMs) in early and mid-level visual cortex, which have generally small pRF sizes that increase more eccentric from fixation (Smith et al, 2001; Dumoulin and Wandell, 2008; Barton and Brewer, 2015)
We provide evidence for four novel VFMs organized into a cloverleaf cluster in the posterior superior temporal sulcus (pSTS) and novel pRF-based analyses of the previously identified, mid-level VFMs V3A and V3B, which together form the V3A/B cloverleaf cluster
Summary
In many mammals, including humans, low and mid-level sensory cortex contains multiple, functionally specialized cortical field maps (CFMs), in which neurons whose sensory receptive fields are positioned next to one another in sensory feature space are located next to one another in cortex (for additional discussion, see Kaas J.H., 1997; Krubitzer, 2007; Wandell et al, 2007; Barton et al, 2012; Brewer and Barton, 2012b, 2016). Measuring the organization of individual VFMs helps differentiate the stages of distinct visual processing pathways and can be used to track how the cortex changes under various disorders (Baseler et al, 1999, 2002, 2011; Morland et al, 2001; Fine et al, 2003; Hoffmann et al, 2003, 2012, 2015; Van Essen, 2003; Chklovskii and Koulakov, 2004; Smirnakis et al, 2005; Wandell et al, 2005; Brewer, 2009; Muckli et al, 2009; Barton and Brewer, 2015). VFMs serve as excellent and reliable localizers for investigations of particular visual functions across individuals (Press et al, 2001; Huk et al, 2002; Brewer et al, 2005; Silver et al, 2005; Sereno and Amador, 2006; Wandell et al, 2007; Amano et al, 2009; Arcaro et al, 2009; Kolster et al, 2009, 2010; Brewer and Barton, 2014)
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