Figure 9

Reconsidering the sulcal patterning in classic studies of ventral occipito-temporal cortex in chimpanzee brains. (A) The medial surface of two chimpanzees (Troglodytes niger) from Retzius (1906). While Retzius only labeled the collateral (co) and calcarine (ca) sulci, each of the sulci that we identify in the present study is identifiable in Retzius’ images. We refer to this as a case in which the MFS is identifiable, but unlabeled. (B) Top: photographs of the ventral surface of four chimpanzee hemispheres (3 right and 1 left) from Mingazzini (1928). In each case, the fusiform (fus, red circle) is mis-labeled and is far too anterior considering modern definitions. Nevertheless, each of the sulci that we identify in the present dataset is identifiable in these images. Additionally, Connolly (1950) also previously commented on the labeling errors in Mingazzini’s (1928) paper (see text). We refer to this as a case in which the MFS is present and unlabeled, while the fusiform gyrus is mis-localized. Bottom: An additional left hemisphere provided by Mingazzini (1928), which (a) identifies the fusiform correctly and (b) only corresponds to the medial fusiform (MFG), while the MFS and lateral fusiform are unlabeled. (C) Left: a labelled schematic of the sulcal patterning within the ventral view of a chimpanzee left hemisphere. Right: the photograph that was used to generate the schematic depicted in the image at left by Bonin et al., 1950. Both the schematic and photograph were used as representative illustrations accompanying the discussion of sulcal patternings in the chimpanzee brain. It is worth noting that Bonin and colleagues mis-identified the collateral sulcus (col). Specifically, what is labeled col is actually the lingual sulcus, which is located medial to the collateral sulcus. Instead, what is labeled otm is actually the collateral sulcus (see text for further explanation). Further, the MFS is also clearly identifiable in addition to the other sulci identified in the present paper. We refer to this as a case in which gyri were accurately identified, but sulci were mischaracterized. Also, note some inaccuracies in the drawing compared to the photograph. For example, the MFS is inaccurately small in the drawn schematic compared to the photograph. (D) Ventral view of a photograph of a chimpanzee brain (“Bonzo”) from Walker and Fulton (1936). The anterior portion of the fusiform gyrus is labeled (F), but the rest of the fusiform is obscured. We consider this as a case in which the fusiform is discussed, but a majority of it is obscured by the cerebellum. (E) An additional photograph of a medial view of a chimpanzee right hemisphere (“Song”) from Walker and Fulton (1936). The collateral sulcus is correctly labeled and the visible sulcal patterning resembles that identified in the present study. Nevertheless, what we identify as the start and end of the MFS (red asterisks) cannot be differentiated from the OTS as this view is too medial. But, as the MFS is immediately lateral to the CoS in every hemisphere examined in both present and historical images, these asterisks almost certainly correspond to the anterior and posterior extents of the MFS. LFG lateral fusiform gyrus, LG lingual gyrus, MFG medial fusiform gyrus, PHG parahippocampal gyrus.