Morphologic evidence for fiber sorting in the fasciculus cuneatus

Culberson, James L.; Albright, B.C.

doi:10.1016/0014-4886(84)90146-8

Cited by 3 publications

(5 citation statements)

References 34 publications

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“…Within the cuneate projections are many fibers which distribute to portions of the CN and EC known to receive proprioceptive inputs. Projections to the dorsal CN, especially in the region near the obex, are abundant; but neither the cells in CN nor the fiber projection seem to be arranged so precisely as those in placental mammals (primates) with well-developed digital dexterity (Albright and Haines, 1978;Culberson and Albright, 1984;Rustioni et al, 1979).…”

Section: Discussionmentioning

confidence: 96%

“…All demanding stages of surgery were performed under microscopic control. After 5 to 6 days postoperative survival (based on prior experience with this fiber system in several species; Culberson and Albright, 1984), animals were anesthetized as described above, injected (intracardiac) with 5,000 units of heparin, and killed by transcardiac perfusion with warm (28-30°C) 0.9% NaCl solution followed by a 10% formalin fixative solution. Brains and spinal cords were removed immediately and stored in fresh 10% formalin for 8 weeks to 6 months before further processing.…”

Section: Methodsmentioning

confidence: 99%

“…In addition, one previous report (Culberson and Albright, 1984) includes some data on the arrangement of cervical dorsal root fibers in the fasciculus cuneatus of three species-the raccoon, potoroo, and brush-tailed possum; however, details of distribution have not been published for any of these. In the present work, the medullary distribution of cervical dorsal root fibers in the brush-tailed possum is presented in detail and discussed in comparison to placental forms already examined.…”

Section: Introductionmentioning

confidence: 95%

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Projection of cervical dorsal root fibers to the medulla oblongata in the brush‐tailed possum, Trichosurus vulpecula

Culberson

1987

Am. J. Anat.

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This study describes the projection of cervical spinal afferent nerve fibers to the medulla in the brush-tailed possum, a marsupial mammal. After single dorsal roots (between C2 and T1) were cut in a series of animals, the Fink-Heimer method was used to demonstrate the projection fields of fibers entering the CNS via specific dorsal roots. In the high cervical spinal cord, afferent fibers from each dorsal root form a discrete layer in the dorsal funiculus. The flattened laminae from upper cervical levels are lateral and those from lower cervical levels are medial within the dorsal columns. All afferent fibers at this level are separated from gray matter by the corticospinal fibers in the dorsal funiculus. All cervical roots project throughout most of the length of the well-developed main cuneate nucleus in a loosely segmentotopic fashion. Fibers from rostral roots enter more lateral parts of the nucleus, and fibers from lower levels pass to more medial areas; but terminal projection fields are typically large and overlap extensively. At more rostral medullary levels, fibers from all cervical dorsal roots also reach the external cuneate nucleus. The spatial arrangement here is more complex and more extensively overlapped than in the cuneate nucleus. Rostral cervical root fibers reach ventral and ventrolateral areas of the external cuneate nucleus and continue to its rostral pole; more caudal root fibers project to more dorsal and medial regions within the nucleus. These results demonstrate that projection patterns of spinal afferents in this marsupial are similar to those seen in the few placental species for which detailed data concerning this system are available.

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Section: Discussionmentioning

confidence: 96%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

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Projection of cervical dorsal root fibers to the medulla oblongata in the brush‐tailed possum, Trichosurus vulpecula

Culberson

1987

Am. J. Anat.

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“…Several aspects may have caused a bias in the results, and hereto explain the differences between the ranges of calculated diameters of the patient models. Although the average fiber diameter is smaller at higher vertebral levels [15], it is assumed that this does not strongly influence the results of this study, since only levels T7-T10 were considered.…”

Section: Discussionmentioning

confidence: 97%

“…Anatomical studies on human and animal spinal cord have shown that generally the topographical organization of the DC's has the form of a fiber lamination, i.e., fibers corresponding to different body segments are lying in parallel layers, approximately normal to the dorsal border of the DC's. The dorsomedial positions are occupied by DC fibers arising from the most caudal DR fibers, whereas fibers originating from more rostral levels join laterally [7]- [15]. No direct functional association has been shown to this structure.…”

Section: Introductionmentioning

confidence: 96%

Estimation of fiber diameters in the spinal dorsal columns from clinical data

Wesselink

Holsheimer²,

Nuttin³

et al. 1998

IEEE Trans. Biomed. Eng.

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Lack of human morphometric data regarding the largest nerve fibers in the dorsal columns (DC's) of the spinal cord has lead to the estimation of the diameters of these fibers from clinical data retrieved from patients with a new spinal cord stimulation (SCS) system. These patients indicated the perception threshold of stimulation induced paresthesia in various body segments, while the stimulation amplitude was increased. The fiber diameters were calculated with a computer model, developed to calculate the effects of SCS on spinal nerve fibers. This computer model consists of two parts: 1) a three-dimensional (3-D) volume conductor model of a spinal cord segment in which the potential distribution due to electrical stimulation is calculated and 2) an electrical equivalent cable model of myelinated nerve fiber, which uses the calculated potential field to determine the threshold stimulus needed for activation. It is shown that the largest fibers in the medial DC's are significantly smaller than the largest fibers in the lateral parts. This finding is in accordance with the fiber distribution in cat, derived from the corresponding propagation velocities. Moreover, it is shown that the mediolateral increase in fiber diameter is mainly confined to the lateral parts of the DC's. Implementation of this mediolateral fiber diameter distribution of the DC's in the computer model enables the prediction of the recruitment order of dermatomal paresthesias following increasing electrical stimulation amplitude.

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Medullary sources of projections to the kinesthetic thalamus in raccoons: External and basal cuneate nuclei and cell groups x and z

Ostapoff

Johnson

Albright

1988

J of Comparative Neurology

138

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In raccoons and other mammals, a pathway for kinesthetic sensation (from muscles, fascia, tendons, and joints) reaches the anterodorsal cap of the ventrobasal thalamus and the anteriormost part of the somatic sensory cerebral cortex. To find the medullary component of this kinesthetic pathway in raccoons, small injections of horseradish peroxidase were made in the thalamus under guidance of simultaneous electrophysiological recording from kinesthetic projections. As determined by retrograde labeling following these injections, kinesthetic thalamic subregions receive projections as follows: caudomedial from cells in the external cuneate nucleus and its medial tongue, rostromedial from cells in basal cuneate nucleus, and rostrolateral from cells in cell group z and the reticular division of cell group x. Electrophysiological recording showed kinesthetic representations in each of these medullary regions. Labeled cells were also observed in the infratrigeminal subnucleus of the lateral reticular nucleus. Cats have kinesthetic projections to the thalamus from the basal cuneate and cell group z; raccoons (and monkeys) have these plus projections from the external cuneate and cell group x. This suggests that the kinesthetic projection system in raccoons and monkeys is expanded in correlation with their more dextrous use of the hand.

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Morphologic evidence for fiber sorting in the fasciculus cuneatus

Cited by 3 publications

References 34 publications

Projection of cervical dorsal root fibers to the medulla oblongata in the brush‐tailed possum, Trichosurus vulpecula

Projection of cervical dorsal root fibers to the medulla oblongata in the brush‐tailed possum, Trichosurus vulpecula

Estimation of fiber diameters in the spinal dorsal columns from clinical data

Medullary sources of projections to the kinesthetic thalamus in raccoons: External and basal cuneate nuclei and cell groups x and z

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