The Paracingulate Sulcus Is a Unique Feature of the Medial Frontal Cortex Shared by Great Apes and Humans

Abstract

Primate brains display a wide range of variation in size and cerebral gyrification, leading to the appearance of novel sulci in particular groups of species. We investigated sulcal organization in the medial frontal cortex of great apes, with a particular focus on the paracingulate sulcus (PCGS). Until recently, the presence of the PCGS was thought to be a structural feature unique to the human brain. However, upon closer examination, the PCGS has been observed as a variable feature that also may appear in chimpanzee brains. To understand the evolutionary origins of the sulcal anatomy in the medial frontal cortex of apes, we examined high-resolution MRI scans for the presence or absence of the PCGS and, when present, measured its length in a sample of ape brains (chimpanzees, bonobos, gorillas, orangutans, gibbons, and siamangs). We found that the PCGS is variable in its appearance among these species, being present in 23 to 50% of great ape individuals depending on the species, but not present in gibbons or siamangs. We did not find population level hemispheric lateralization patterns or sex differences in PCGS presence across species, and we did not detect a relationship between cerebral volume and PCGS occurrence or length. Our data suggest that the PCGS is a common sulcal variant present in great apes and humans due to a shared evolutionary ancestry.

Evolution of human language: duetting as part of prosociality and cognition

“…In primates, this abstract ability to be able to deal with symbolic representations of language and thus display complex cognitive processes led to a host of detailed investigations both of behavior and of the structure and function of the primate brain (Maestripieri, 1999;Reader and Laland, 2002). Such investigations and comparative studies between primates and humans continue to this day and have clarified differences (Palomero-Gallagher and Zilles, 2019) and similarities (Miller et al, 2021) between the brain of apes and the human brain. The discoveries of mental time travel (conceiving of past, present, and future) conveyed in sign language added depth to the view that apes are cognitively very advanced, can readily cope with abstract concepts, and imbue gestures with meaning (Leavens, 2004;Liebal and Call, 2012;Fröhlich and Hobaiter, 2018;Hobaiter et al, 2022).…”

Sulcal morphology of posteromedial cortex substantially differs between humans and chimpanzees

“…Such studies have revealed that although the sulcal patterning of primary sensory cortices more or less resembles one another 20 across species, this relationship is far less consistent in association cortices. For example, while the sulcal organization of visual association cortex was comparable between every human and non-human hominoid hemisphere examined in previous work 15 , the incidence of sulci in medial 14,16,17 and lateral 38 prefrontal cortex, as well as orbitofrontal cortex 64 was substantially different across species. Adding to the complexity, within each of these regions, differences in sulcal incidence rates were greater for some sulci compared to others -elucidating specific areas of cortex that are particularly expanded/more complex in humans.…”

“…A fundamental question in comparative biology and systems neuroscience is: What features of the brain are unique to humans? Key insights regarding what features of the brain are unique to humans have been gleaned from studies comparing anatomical and functional features of the human brain to features from the brains of our close evolutionary relative, the chimpanzee [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . Of all the features to study, researchers particularly focus on the folds of the cerebral cortex, or sulci, as they generally track with evolutionary complexity 21 .…”

Non-human contributions to personality neuroscience – from fish through primates. An introduction to the special issue

“…In sum, fundamental aspects of emotional traits and of psychopathology are controlled in humans by conserved systems including diffuse ascending components that terminate throughout the neocortex (Dubois, Galdi, Han, Paul, & Adolphs, 2018;Dubois et al, 2020). This allows non-humans, from fish through primates, to provide meaningful models (with true homologies) of the core emotion production systems through which the complex sensory filters of more recently evolved cortical systems (Falcone et al, 2020;Miller, Hof, Sherwood, & Hopkins, 2021) change affect, behaviour, cognition, and desire. Both between and within species, trait aspects of these systems depend on genes and their interaction with the developmental environment of the organism.…”