Comparative neocortical neuromorphology in felids: African lion, African leopard, and cheetah

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The African wild dog is endemic to sub‐Saharan Africa and belongs to the family Canidae which includes domestic dogs and their closest relatives (i.e., wolves, coyotes, jackals, dingoes, and foxes). The African wild dog is known for its highly social behavior, co‐ordinated pack predation, and striking vocal repertoire, but little is known about its brain and whether it differs in any significant way from that of other canids. We employed gross anatomical observation, magnetic resonance imaging, and classical neuroanatomical staining to provide a broad overview of the structure of the African wild dog brain. Our results reveal a mean brain mass of 154.08 g, with an encephalization quotient of 1.73, indicating that the African wild dog has a relatively large brain size. Analysis of the various structures that comprise their brains and their topological inter‐relationships, as well as the areas and volumes of the corpus callosum, ventricular system, hippocampus, amygdala, cerebellum and the gyrification index, all reveal that the African wild dog brain is, in general, similar to that of other mammals, and very similar to that of other carnivorans. While at this level of analysis we do not find any striking specializations within the brain of the African wild dog, apart from a relatively large brain size, the observations made indicate that more detailed analyses of specific neural systems, particularly those involved in sensorimotor processing, sociality or cognition, may reveal features that are either unique to this species or shared among the Canidae to the exclusion of other Carnivora.

Section: Discussionmentioning

confidence: 99%

Brain of the African wild dog. I. Anatomy, architecture, and volumetrics

Chengetanai

Tenley

Bertelsen

et al. 2020

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“…We thus needed a model that could address these specific confounds. (Hastie, Tibshirani, & Friedman, 2009) robust to violations of normality, nonhomogeneity of variability, and independence (Butti et al, 2015;Jacobs et al, 2014Jacobs et al, , 2015Johnson et al, 2016;Nguyen et al, 2020 3 | RESULTS…”

Section: Discussionmentioning

confidence: 99%

“…In this case, a multivariate adaptive regression splines (MARSplines, Statistica, release 13.3; StatSoft, Austin, TX; Friedman, 1991) analysis was used with the confounds in the model, making their contribution explicit and evaluable. MARSplines is a quantitative, nonparametric methodology (Hastie, Tibshirani, & Friedman, 2009) robust to violations of normality, nonhomogeneity of variability, and independence (Butti et al, 2015;Jacobs et al, 2014Jacobs et al, , 2015Johnson et al, 2016;Nguyen et al, 2020). It was limited to a maximum of 30 basis functions, up to sixth-order interactions to accommodate the three confounds and the dendritic measures, a threshold of 0.0005, pruning was allowed, and penalty was set at 2.…”

Section: Discussionmentioning

confidence: 99%

“…Although such hypotheses are typically evaluated using parametric tests for means (e.g., t tests or analysis of variances), there were three concerns about the appropriateness of such analytic approaches. First, past research (Jacobs et al, 2014(Jacobs et al, , 2015(Jacobs et al, , 2018Johnson et al, 2016;Nguyen et al, 2020) indicated that some dendritic measures would not be normally distributed (with leptokurtoses being the most common issue), violating the normality assumptions of most such tests. Second, the data were repeated measurements (in the statistical sense) of the same neuronal branch, with each dendrite in turn nested within neuron, area, hemisphere, and brain.…”

Section: Discussionmentioning

confidence: 99%

“…For basilar dendrites, the first three orders of segments were classified as proximal branches; fourth-order and above were classified as distal. Six previously established measures (Butti et al, 2015;Jacobs et al, 1997Jacobs et al, , 2011Nguyen et al, 2020) were used to characterize each neuron's dendritic systems: dendritic volume (Vol, μm 3 : the total volume of all dendrites), TDL (μm: the summed length of all dendritic segments), mean segment length (MSL, μm: the average length of each dendritic segment), dendritic segment count (DSC, the number of dendritic segments), DSN (the total number of spines on each neuron), and dendritic spine density (DSD, the average number of spines per μm of dendritic length). In addition, dendritic diameter (Dia, μm: the average thickness of individual dendritic processes) was measured.…”

Section: Quantitative Dendritic and Spine Measuresmentioning

confidence: 99%

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Putative dendritic correlates of chronic traumatic encephalopathy: A preliminary quantitative Golgi exploration

Warling

Uchida

Shin

et al. 2020

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Chronic traumatic encephalopathy (CTE) is a neurodegenerative disorder that is associated with repetitive head impacts. Neuropathologically, it is defined by the presence of perivascular hyperphosphorylated tau aggregates in cortical tissue (McKee et al., 2016, Acta Neuropathologica, 131, 75-86). Although many pathological and assumed clinical correlates of CTE have been well characterized, its effects on cortical dendritic arbors are still unknown. Here, we quantified dendrites and dendritic spines of supragranular pyramidal neurons in tissue from human frontal and occipital lobes, in 11 cases with (M age = 79 ± 7 years) and 5 cases without (M age = 76 ± 11 years) CTE. Tissue was stained with a modified rapid Golgi technique. Dendritic systems of 20 neurons per region in each brain (N = 640 neurons) were quantified using computer-assisted morphometry. One key finding was that CTE neurons exhibited increased variability and distributional changes across six of the eight dendritic system measures, presumably due to ongoing degeneration and compensatory reorganization of dendritic systems. However, despite heightened variation among CTE neurons, CTE cases exhibited lower mean values than Control cases in seven of the eight dendritic system measures. These dendritic alterations may represent a new pathological marker of CTE, and further examination of dendritic changes could contribute to both mechanistic and functional understandings of the disease.

Betz cells of the primary motor cortex

Nolan,

Scott,

Hof

et al. 2024

Betz cells, named in honor of Volodymyr Betz (1834–1894), who described them as “giant pyramids” in the primary motor cortex of primates and other mammalian species, are layer V extratelencephalic projection (ETP) neurons that directly innervate α‐motoneurons of the brainstem and spinal cord. Despite their large volume and circumferential dendritic architecture, to date, no single molecular criterion has been established that unequivocally distinguishes adult Betz cells from other layer V ETP neurons. In primates, transcriptional signatures suggest the presence of at least two ETP neuron clusters that contain mature Betz cells; these are characterized by an abundance of axon guidance and oxidative phosphorylation transcripts. How neurodevelopmental programs drive the distinct positional and morphological features of Betz cells in humans remains unknown. Betz cells display a distinct biphasic firing pattern involving early cessation of firing followed by delayed sustained acceleration in spike frequency and magnitude. Few cell type‐specific transcripts and electrophysiological characteristics are conserved between rodent layer V ETP neurons of the motor cortex and primate Betz cells. This has implications for the modeling of disorders that affect the motor cortex in humans, such as amyotrophic lateral sclerosis (ALS). Perhaps vulnerability to ALS is linked to the evolution of neural networks for fine motor control reflected in the distinct morphomolecular architecture of the human motor cortex, including Betz cells. Here, we discuss histological, molecular, and functional data concerning the position of Betz cells in the emerging taxonomy of neurons across diverse species and their role in neurological disorders.