Two New Cytoarchitectonic Areas on the Human Mid-Fusiform Gyrus

Abstract

Areas of the fusiform gyrus (FG) within human ventral temporal cortex (VTC) process high-level visual information associated with faces, limbs, words, and places. Since classical cytoarchitectonic maps do not adequately reflect the functional and structural heterogeneity of the VTC, we studied the cytoarchitectonic segregation in a region, which is rostral to the recently identified cytoarchitectonic areas FG1 and FG2. Using an observer-independent and statistically testable parcellation method, we identify 2 new areas, FG3 and FG4, in 10 human postmortem brains on the mid-FG. The mid-fusiform sulcus reliably identifies the cytoarchitectonic transition between FG3 and FG4. We registered these cytoarchitectonic areas to the common reference space of the single-subject Montreal Neurological Institute (MNI) template and generated probability maps, which reflect the intersubject variability of both areas. Future studies can relate in vivo neuroimaging data with these microscopically defined cortical areas to functional parcellations. We discuss these results in the context of both large-scale functional maps and fine-scale functional clusters that have been identified within the human VTC. We propose that our observer-independent cytoarchitectonic parcellation of the FG better explains the functional heterogeneity of the FG compared with the homogeneity of classic cytoarchitectonic maps.

A map of the human neocortex showing the estimated overall myelin content of the individual architectonic areas based on the studies of Adolf Hopf

“…The anterior portion of the basal temporal dark cluster, which comprises the areas 175 and 176 of our map (Fig. 6), clearly corresponds with the cytoarchitectonic area 20tc of Sarkissov et al (1955); the posterior part of this cluster, which includes the areas 173, 174, 177, 179 and 180 of our map, roughly corresponds with the cytoarchitectonic areas FG3 and FG4, recently described by Lorenz et al (2015). …”

Cortical representation of persistent visual stimuli

“…These results provide evidence that regions which appear homogenous in terms of their category-selectivity (Tsao et al, 2006), but are anatomically and cytoarchitectonically distinct (Caspers et al, 2013; Grill-Spector and Weiner, 2014; Lorenz et al, 2015), differ in how they respond to a stimulus over time and in their potential contribution to ongoing visual perception.…”

“…Two additional posterior fusiform electrodes, located medial to the mid-fusiform sulcus, were also object-selective and duration-tracking, however their selectivity was limited to the onset response, that is, the response to faces and objects did not differ in the late (1200–1500 ms) time window. The locations of the two face-selective electrodes correspond to the posterior fusiform face-selective region pFus-faces (or FFA-1, Grill-Spector and Weiner, 2014), and to cytoarchitectonic region FG2 (Caspers et al, 2013), suggesting a functional distinction between this region and the more anterior mFus-faces region (FFA-2, related to cytoarchitectonic area FG4, Lorenz et al, 2015), which showed high category selectivity but little duration-tracking.…”

Influence of task instructions and stimuli on the neural network of face processing: An ALE meta-analysis

“…Details on the cytoarchitectonic regions referred to in the results tables may be found in the following publications reporting on Broca’s region (Amunts et al, 1999), motor cortex (Geyer et al, 1996), somatosensory cortex (Geyer, Schleicher, & Zilles, 1999; Grefkes, Geyer, Schormann, Roland, & Zilles, 2001), amygdala and hippocampus (Amunts et al, 2005), visual cortex (Amunts, Malikovic, Mohlberg, Schormann, & Zilles, 2000), lateral occipital and ventral extrastriate cortex (Malikovic et al, 2015; Rottschy et al, 2007), cerebellum (Diedrichsen, Balsters, Flavell, Cussans, & Ramnani, 2009), posterior fusiform gyrus (J. Caspers et al, 2013), mid-fusiform gyrus (Lorenz et al, 2015), basal forebrain (Zaborszky et al, 2008) and thalamus (connectivity-based regions: Behrens et al, 2003). …”