An analysis of von Economo neurons in the cerebral cortex of cetaceans, artiodactyls, and perissodactyls
Anatomy & Morphology; anterior cingulate cortex; bowhead whale; brain; cetartiodactyla; Cingulate; cortex; Cortical evolution; evolution; evolution; Fork cells; frontoinsular cortex; great apes; Insula; Neurosciences & Neurology; phylogeny; spindle neurons; variant frontotemporal dementia; Von Economo neurons (VENs); whale
Von Economo neurons (VENs) are specialized projection neurons with a characteristic spindle-shaped soma and thick basal and apical dendrites. VENs have been described in restricted cortical regions, with their most frequent appearance in layers III and V of the anterior cingulate cortex, anterior insula, and frontopolar cortex of humans, great apes, macaque monkeys, elephants, and some cetaceans. Recently, a ubiquitous distribution of VENs was reported in various cortical areas in the pygmy hippopotamus, one of the closest living relatives of cetaceans. That finding suggested that VENs might not be unique to only a few species that possess enlarged brains. In the present analysis, we assessed the phylogenetic distribution of VENs within species representative of the superordinal clade that includes cetartiodactyls and perissodactyls, as well as afrotherians. In addition, the distribution of fork cells that are often found in close proximity to VENs was also assessed. Nissl-stained sections from the frontal pole, anterior cingulate cortex, anterior insula, and occipital pole of bowhead whale, cow, sheep, deer, horse, pig, rock hyrax, and human were examined using stereologic methods to quantify VENs and fork cells within layer V of all four cortical regions. VENs and fork cells were found in each of the species examined here with species-specific differences in distributions and densities. The present results demonstrated that VENs and fork cells were not restricted to highly encephalized or socially complex species, and their repeated emergence among distantly related species seems to represent convergent evolution of specialized pyramidal neurons. The widespread phylogenetic presence of VENs and fork cells indicates that these neuron morphologies readily emerged in response to selective forces,whose variety and nature are yet to be identified.
Raghanti M A; Spurlock L B; Treichler F R; Weigel S E; Stimmelmayr R; Butti C; Thewissen Jgmh; Hof P R
Brain Structure & Function
2015
2015-07
Journal Article
<a href="http://doi.org/10.1007/s00429-014-0792-y" target="_blank" rel="noreferrer noopener">10.1007/s00429-014-0792-y</a>
Subnasoalveolar anatomy and hominoid phylogeny: Evidence from comparative ontogeny
Anthropology; Evolutionary Biology; evolution; allometry; great apes; miocene; form; sexual dimorphism; extant; fossil hominids; Homo; late; african apes; facial kyphosis; character phylogeny; chimp; hylobatids; ontogenetic; orangutans; skull material; subnasal development
The present analysis evaluated extant hominoid subnasal morphological variation from an ontogenetic perspective, documenting both qualitative and allometric details of subnasal maturation in Hylobates, great apes and modern humans. With respect to intraspecific variation, results of log-linear modeling procedures indicate that qualitative features of the subnasal region shown previously to discriminate extant taxa (Ward and Kimbel, 1983; McCollum et al., 1993) do not vary appreciably with either age or sex. In terms of quantitative variation, aside from observed changes in the position of the anterior attachment of the nasal septal cartilage relative to the lateral margins of the nasal cavity, the morphology of the subnasal region does not vary appreciably with age. Furthermore, it was found that sexual dimorphism in subnasal form is present only in Pongo and Gorilla and is the result of sexual bimaturism rather than sexual variation in canine size. In considering interspecific variation in subnasal form, there is a propensity among hominoid taxa for the nasal cavity floor to be free of substantial topographic relief. The smoothly continuous nasal floor topography identified in the majority of hominoid taxa appears to be produced by extensive resorption of the anterior nasal cavity floor that accompanies an upward rotation of the anterior maxilla during craniofacial ontogeny. Comparisons of ontogenetic allometric trajectories indicate that relatively little of the variation in hominoid subnasal form can easily be attributed to variation in body/cranial size. Instead, variation in craniofacial orientation, vascular anatomy and incisor size and inclination were identified as potential mediators of hominoid subnasoalveolar anatomy. Although results of this analysis confirm that many details of the orangutan subnasal morphology are derived for this taxon, there is little conclusive evidence to support recent reports that the morphology displayed by Gorilla is primitive for great apes (Begun, 1992, 1994). (C) 1997 Wiley-Liss, Inc.
McCollum M A; Ward S C
American Journal of Physical Anthropology
1997
1997-03
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1002/(sici)1096-8644(199703)102:3%3C377::aid-ajpa7%3E3.0.co;2-s" target="_blank" rel="noreferrer noopener">10.1002/(sici)1096-8644(199703)102:3%3C377::aid-ajpa7%3E3.0.co;2-s</a>