The pyramidal tract. An enumeration of the large motor cells of area 4 and the axons in the pyramids of the chimpanzee

Lassek, A. M.; Wheatley, M. D.

doi:10.1002/cne.900820305

Cited by 10 publications

(3 citation statements)

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“…With respect to the total number of Betz cells per hemisphere, the values reported by Campbell (1905), Lassek (1940), and Lassek and Wheatley (1945) represent underestimates by a factor of 3.6 in comparison to our results. These considerable discrepancies can be explained by the differences in the techniques used.…”

Section: Characteristics Of Betz Cells Vs Layer V Pyramidal Cellscontrasting

confidence: 97%

“…This size reduction appears to be related to motor somatotopy: the largest cells are found in the region of foot and leg representation, where efferent axons project the farthest along the corticospinal tract. The values reported in early studies for the total number of Betz cells in one human hemisphere range from 25,000 (Campbell, 1905), to 34,370 (Lassek, 1940;Lassek and Wheatley, 1945;Blinkov and Glezer, 1968), and up to 40,000 (Scheibel and Scheibel, 1978). Lassek (1940) demonstrated that the numerical distribution of Betz cells is related to somatotopy, with 75% of all Betz cells being in the leg area, 17.9% in the arm region, and 6.6% in the head area.…”

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Stereologic characterization and spatial distribution patterns of Betz cells in the human primary motor cortex

et al. 2003

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Betz cells are giant motoneurons located in layer Vb of the primate primary motor cortex. We conducted stereological analyses of Betz cells and neighboring pyramidal cells from the brains of six neurologically normal elderly humans to determine their volume, total number, and spatial distribution, and to relate these data to functional localization. The distribution of cellular volumes exhibits a bimodal pattern, delineating two different subpopulations. Betz cell volumes follow a mediolateral gradient, the largest Betz cells being located on the most medial part of the motor cortex. Additionally, the shape of Betz cells varies between the rostral and caudal parts of the primary motor cortex, supporting the notion that there are anatomically distinct zones in primary motor cortex. The total number of Betz cells per hemisphere accounts for about one-tenth of the total number of pyramidal cells in layer Vb. Analysis of spatial distribution using Voronoi tessellation revealed maximal clustering of Betz cells in a zone situated two-thirds from the midline along the mediolateral axis of the primary motor cortex. These data suggest that Betz cells have a discrete subregional distribution that may correspond to certain aspects of the functional parcellation of area 4. These results may offer a histological correlate of functional imaging studies and are relevant in the context of neurodegenerative diseases such as amyotrophic lateral sclerosis, progressive supranuclear palsy, and Guamanian amyotrophic lateral sclerosis/Parkinsonism-dementia, and in studies of normal brain aging. Anat Rec Part A 270A: 137-151, 2003. © 2003 Key words: amyotrophic lateral sclerosis; area 4; Betz cells; cytoarchitecture; human neocortex; motoneurons; stereologyThe human neocortex is characterized by regional and laminar specific distributions of a variety of neuronal subtypes and distinct afferent and efferent connections. The neocortex can be parcellated into a large number of more or less distinct fields according to microscopic architecture. Identification of the primary motor cortex and its boundaries, however, has been particularly contentious. Brodmann (1903Brodmann ( , 1909 originally described area 4 as an agranular zone, delineated by the presence of Betz cells, a subpopulation of giant infragranular pyramidal neurons in cortical layer V, located on its rostral border and buried in the depth of the anterior wall of the central sulcus. This definition has since been criticized (Zeki, 1979), and Brodmann's original delineation of the primary motor cortex has been revised by other investigators, who described an intermediate precentral area, an area precentralis A, area

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Section: Characteristics Of Betz Cells Vs Layer V Pyramidal Cellscontrasting

confidence: 97%

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confidence: 99%

Stereologic characterization and spatial distribution patterns of Betz cells in the human primary motor cortex

et al. 2003

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“…One possible reason for this difference between areas F2d and F2v may be a differential distribution of ‘slow’ and ‘fast’ pyramidal tract neurons (PTNs, Brookhart 1952). According to Verhaart (1948) 10% of pyramidal tract fibres have axonal diameters of up to 3 μm (‘fast’ PTNs), but giant pyramidal cells may account for only 3% of the descending projection (Lassek & Wheatley 1945). Therefore, at least 7% of ‘fast’ PTNs should originate from big pyramids that are not classifiable as giant pyramidal cells.…”

Section: Discussionmentioning

confidence: 99%

Neurofilament protein distribution in the macaque monkey dorsolateral premotor cortex

Geyer

Zilles²,

Luppino

et al. 2000

Eur J of Neuroscience

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Regional and laminar distribution patterns of neurofilament proteins in the dorsolateral premotor cortex (PMd) were studied with monoclonal antibody SMI-32 in five adult macaque monkeys and compared with the cytoarchitectonical features of the PMd. Our goal was to reveal whether the increasing functional diversity of the PMd which electrophysiological studies have unravelled over the last years is reflected on a structural level by differences in the neurochemical phenotype. Differences in size, shape and packing density of immunopositive layer III and V pyramidal cells define areas much more clearly than do differences in cytoarchitecture. The PMd can be subdivided into a rostral and a caudal part at a level slightly anterior to the genu of the arcuate sulcus. The extent of these two areas matches the two cytoarchitectonically defined areas F7 and F2, respectively. Within area F2, differences in layer V immunoreactive neurons define a dorsal (F2d) and a ventral (F2v) region. The border between areas F2d and F2v lies at the superior precentral dimple and cannot be detected cytoarchitectonically in Nissl-stained sections. Neurofilament proteins are involved in the stabilization of the cytoskeleton of the axon and have been correlated with axonal size and conduction velocity of nerve fibres. This regional variability in the neurochemical phenotype of layer V within the caudal PMd may reflect a differential organization of the descending output from this part of the premotor cortex. It might also be related to differences in the motor control of voluntary arm and leg movements.

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The pyramidal tract of an aquatic carnivore (seal)

Lassek¹,

Karlsberg²

1956

J of Comparative Neurology

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ONE FIGUREThe mammals, the pyramidal tract of which has not been investigated, are ones not easily obtained, such as the whale, elephant, porpoise, spiny ant-eater, bat, and seal, among others. Each of these has its own special type of motor activity and locomotion, some of it depending upon whether its natural habitat is on land, in the sea or in the air. All are suitable for certain anatomical studies of the pyramidal bundle because it has a consistent and isolated location in the pyramid of the medulla oblongata. By contrast, these hard-to-get animals do not lend themselves easily to physiological laboratory procedures.Although the pyramidal tract has long been considered to be concerned with the innervation of the striated muscles of the body, recent investigations, of an electrophysiological and ablative nature, indicate that it may also serve in the propagation of cortical autonomic impulses from pre-and postcentral areas mediated via small fibers (Brookhart and Morris, '48 ; Landau, '53 ; Spiegel and Hunsicker, '36 ; Spiegel et al., '43). I n the light of this, a spectral analysis of its fibers in any species may be of value in correlating dual types of physiology: transmission of impulses to autonomic as well as to somatic efferent neurons.

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The pyramidal tract. An enumeration of the large motor cells of area 4 and the axons in the pyramids of the chimpanzee

Cited by 10 publications

References 3 publications

Stereologic characterization and spatial distribution patterns of Betz cells in the human primary motor cortex

Stereologic characterization and spatial distribution patterns of Betz cells in the human primary motor cortex

Neurofilament protein distribution in the macaque monkey dorsolateral premotor cortex

The pyramidal tract of an aquatic carnivore (seal)

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