The course of efferent fibers from the human premotor cortex

Minckler, Jeff; Klemme, Roland M.; Minckler, Dona

doi:10.1002/cne.900810303

Cited by 25 publications

(3 citation statements)

References 13 publications

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“…The distinction between 'frontal' and 'motor' cortex (areas 6 and 4) is clear histologically and occurs approximately at the junction of the medial third and lateral twothirds of the anterior sigmoid gyrus (Campbell, 1905;Winkler & Potter, 1914;Langworthy, 1928). Evidence of a contribution from area 6 to the pyramidal tract in monkey and man is doubtful as there are conflicting reports in the literature (Mettler, 1935;Hoff, 1935;Kennard, 1935;Levin, 1936;Verhaart & Kennard, 1940;Minckler, Klemme & Minckler, 1944). Time relations of the few spikes recorded from the frontal region in the present study indicate that any fibres arising from this area are of slow conduction velocity, therefore fine in calibre and difficult to trace by any histological method, a difficulty that may account for the inconclusive findings in experimental work in the monkey.…”

Section: Discussionmentioning

confidence: 99%

Origin of the pyramidal tract in the cat*

Lance¹,

Manning²

1954

The Journal of Physiology

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Woolsey & Chang (1947) introduced a new technique into the study of the origin of the pyramidal tract when they recorded the arrival of antidromic pyramidal activity, initiated from the medulla oblongata, at the surface of the cortex. The present investigation has largely employed this useful method which has been extended by the insertion of microelectrodes into the cell layers of the cortex. By this means the electrical activity of single cells or groups of cells may be recorded as the cell bodies are depolarized by impulses passing antidromically up their axons. Accurate localization of cells giving rise to the pyramidal tract is thus possible, and the conduction velocities oftheir respective axons may be estimated. Results obtained by this method have been checked by the electrical stimulation of small areas of cortex and recording the consequent orthodromic pyramidal activity in medulla or cord. METHODSA series of twenty-five adult cats were used for these experiments. The animals were anaesthetized by Dial (Ciba) 0-5 ml./kg intraperitoneally, an additional 0-2-04 ml. of pentobarbitone solution (gr. 1/ml., 'Sagatal', May and Baker) being administered if necessary. After tracheal cannulation, the pyramidal tract was exposed in the medulla or cord by one of the following methods.(1) Ventral approach to the medulla, by removal of larynx, part of pharynx and oesophagus. The longi capitis muscles were then reflected and a window made in the basiocciput with a dental burr. This approach enabled stimulating or recording electrodes to be placed directly in the pyramid with the animal in the lateral position.(2) Dorsal approach to the fourth ventricle by removal of part of the occipital bone and cerebellum. Electrodes could then be inserted into the pyramids through the medulla, the animal being in the anatomical position.(3) Laminectomy, exposing the spinal cord at cervical or lumbar segments, so that electrodes could be inserted into the lateral corticospinal tract.

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Section: Discussionmentioning

confidence: 99%

Origin of the pyramidal tract in the cat*

Lance¹,

Manning²

1954

The Journal of Physiology

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“…However, BA 4 cannot be assumed to be the only cortical source for PT fibres. Non-primary motor and primary somatosensory cortices also give origin to PT fibres (Minckler et al, 1944;Zilles, 1990). Especially fibres which originate from PRG outside BA 4 in the premotor cortex and in the supplementary motor area may have contributed to the observed asymmetrical pattern of PRPT in the present study.…”

Section: Relationship Between Ba 4 and Prpt In The Same Brainsmentioning

confidence: 99%

Variability and asymmetry in the human precentral motor system: A cytoarchitectonic and myeloarchitectonic brain mapping study

Rademacher

Bürgel²,

Geyer³

et al. 2001

Brain

200

131

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The morphology of the region of the primary motor cortex in the human brain is variable, and putative asymmetries between the hemispheres have been noted since the beginning of last century. Such variability may confound the results of clinical lesion or functional activation studies. We measured Brodmann area (BA) 4 and the identifiable precentral component of the pyramidal tract (PRPT) in 11 human post-mortem brains using techniques of quantitative cytoarchitectonic and myeloarchitectonic image analysis. Topography and variability in the localization of architectonic borders were analysed and mapped to a computerized spatial reference system, which consists of an individual in vivoMRI brain. All maps were superimposed to produce probabilistic maps of BA 4 and PRPT which can be co-registered with any image of brain structure or function that has also been transformed to Talairach coordinates. These maps can be readily applied to future brain mapping studies. We observed a considerable degree of variability between hemispheres (intra-individual) and between brains (inter-individual). The variation zones of BA 4 and PRPT differ from the templates of the Talairach atlas. Voxel-based morphometry shows significant side differences with larger volumes of PRPT in the left hemisphere than in the right hemisphere. This larger volume of the descending cortical motor fibres may be related to the known left-hemisphere dominance for handedness in >90% of the population. In contrast, BA 4 was symmetrically organized. The lack of a significant correlation between the size of BA 4 and the size of PRPT may relate to the fact that additional non-primary motor and sensory cortices contribute to the origins and size of the pyramidal tract proper.

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“…It also remains possible that, in humans, corticobulbar branches of pyramidal tract neurons could more profoundly influence reticulospinal neurons than in smaller primates. However, there is anatomical evidence that in humans many projections of the premotor cortex descend in the pyramidal tracts directly to the spinal cord without terminating significantly in reticulospinal tegmental nuclei (Minckler et al, 1944;Kuypers, 1958), so this possibility seems an unlikely explanation for the corticalization of motor control in the human species.…”

Section: Discussionmentioning

confidence: 96%

Corticalization of motor control in humans is a consequence of brain scaling in primate evolution

Herculano‐Houzel

Kaas

Oliveira‐Souza

2015

J of Comparative Neurology

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Control over spinal and brainstem somatomotor neurons is exerted by two sets of descending fibers, corticospinal/pyramidal and extrapyramidal. Although in nonhuman primates the effect of bilateral pyramidal lesions is mostly limited to an impairment of the independent use of digits in skilled manual actions, similar injuries in humans result in the locked-in syndrome, a state of mutism and quadriplegia in which communication can be established only by residual vertical eye movements. This behavioral contrast makes humans appear to be outliers compared with other primates because of our almost total dependence on the corticospinal/pyramidal system for the effectuation of movement. Here we propose, instead, that an increasing preponderance of the corticospinal/pyramidal system over motor control is an expected consequence of increasing brain size in primates because of the faster scaling of the number of neurons in the primary motor cortex over the brainstem and spinal cord motor neuron pools, explaining the apparent uniqueness of the corticalization of motor control in humans.

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The course of efferent fibers from the human premotor cortex

Cited by 25 publications

References 13 publications

Origin of the pyramidal tract in the cat*

Origin of the pyramidal tract in the cat*

Variability and asymmetry in the human precentral motor system: A cytoarchitectonic and myeloarchitectonic brain mapping study

Corticalization of motor control in humans is a consequence of brain scaling in primate evolution

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