Fig. 3: Impact of the presentce of a PCGS on the cytoarchitectonic organization of the anterior MCC.

Cytoarchitectonic organization of the anterior MCC in hemispheres without (a) and with (b) a PCGS. a The MCC of the left hemisphere of CHIMP_1 is presented on a sagittal view of a post-mortem MRI scan (left panel). The CGS is marked in red. The coronal section presented on the middle panel corresponds to the antero-posterior level defined by a black line on the MRI image (slice 482). The right panels present the labeled and raw Nissl-stained slices. The black lines represent the limits between areas. The gray zones identified by a blue arrow correspond to transition zones between two adjacent cytoarchitectonic areas. Area 24c′ occupies the ventral bank of the CGS and area 32′ occupies the dorsal bank of the CGS. The photomicrographs of area 32′ (corresponding to the region identified by a blue box on the coronal section) and area 24c′ (corresponding to the region identified by a green box on the coronal section) are displayed on the right panels. Results show the presence of a dysgranular layer 4 (in red are displayed the granular patches) in area 32′ and the absence of this layer in area 24c′. b The MCC of the right hemispheres of CHIMP_3 and CHIMP_1 are presented on sagittal views of post-mortem MRI scans. The CGS is marked in red, the PCGS in orange. The coronal sections presented on each Nissl-stained slices correspond to the antero-posterior levels defined by a black line on the MRI images (CHIMP_3: slice 781, CHIMP_1: slice 821). In both chimpanzees, area 24c′ occupies the ventral bank, the fundus, and the lateral-most part of the dorsal bank of the CGS. Area 32′ occupies the dorsal bank of the CGS, the gyrus between the CGS and the PCGS and the ventral bank of the PCGS. CGS cingulate sulcus, MRI magnetic resonance imaging, PCGS paracingulate sulcus, L1-6 cytoarchitectonic layers 1-6, SWM superficial white matter.