A comparative quantitative analysis of cytoarchitecture and minicolumnar organization in Broca's area in humans and great apes

Abstract

Broca's area was identified in the inferior frontal gyrus of chimpanzee, bonobo, gorilla, and orangutan brains through direct cytoarchitectonic comparison with human brains. Across species, Broca's area comprises Brodmann's areas 44 and 45. We found that these areas exhibited similar cytoarchitectonic characteristics in all species examined. We analyzed the minicolumnar organization of cells in layer III of Broca's area in 11 human and 9 great ape specimens. A semiautomated method was used to analyze digitized images of histological sections stained for Nissl substance. Horizontal spacing distance and gray level index (GLI; or the area fraction occupied by cells) were quantified in all images. In contrast to area Tpt, the only cortical area for which comparative minicolumnar data have been published previously for humans and one of the great apes, we found no population-level asymmetry, for either horizontal spacing distance or GLI. Only human females exhibited a leftward asymmetry in GLI. GLI was lower in humans than in great apes (P < 0.001), allowing more space for connectivity in layer III. In humans, horizontal spacing distance was greater than in great apes but smaller relative to brain size.

A rostro-caudal axis for language in the frontal lobe: The role of executive control in speech production

“…Overall, the evidence emerging from these studies coheres with various reports of behavioral and cognitive deficits following frontal damage (Lhermitte et al, 1972;Dreher et al, 2008;Badre et al, 2009;Azuar et al, 2014). Anatomical (Pandya and Yeterian, 1996;Jacobs et al, 2001;Semendeferi et al, 2001Semendeferi et al, , 2011Schenker et al, 2008) and single-cell recording data also bring further substantial support for a pFC gradient in temporal and representational generality (Rao et al, 1997;Fuster et al, 2000;Buckley et al, 2009;Rigotti et al, 2013). Taken together, these findings provide substantial support for hierarchical approaches to human behavior (see Badre, 2008and Botvinick, 2008for reviews and Reynolds et al, 2012and Crittenden and Duncan, 2012 for counter-arguments), some of which came to promote a similar subdivision of frontal systems underlying the various levels of language processing (Fuster, 1989(Fuster, , 1995(Fuster, , 2004Koechlin and Jubault, 2006;Goldberg, 2009).…”

Representation of Numerical and Sequential Patterns in Macaque and Human Brains

“…Compared to macaques, humans exhibit a much stronger coupling between auditory association areas and IFG, including the specific pSTS/BA44 network identified here [43]. Anatomically, the human IFG is expanded and more asymmetrical, its mini columns are more spaced [44], and it connects to the temporal lobe via a prominent fiber tract, the arcuate fasciculus, which is much smaller or absent in other non-human primates [45]. All of these observations concur to suggest an important anatomical, functional, and, possibly, representational change in those regions.…”

Word learning is mediated by the left arcuate fasciculus

“…Comparative studies indicate that apes and monkeys have homologs for Broca's and Wernicke's areas in terms of gray matter (49,50) connected by a dorsal and a ventral pathway (49). However, the trajectory of the AF is different between species.…”