Mechanosensory projections to cuneate, gracile, and external cuneate nuclei in a tree squirrel (fox squirrel, Sciurus Niger)

Ostapoff, E.-Michael; Johnson, John Irwin; Albright, B.C.

doi:10.1016/0306-4522(83)90050-7

Cited by 24 publications

(10 citation statements)

References 21 publications

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“…At similar levels, C5 and C6 segments had dense focal projections ven tral to the C,s terminal zone. Those patterns included the territory where palmar pads were shown to be represented and support the finding that ulnar digits were mapped dorsal to radial digits [Ostapoff et al, 1982]. The central and ventral projection sites in both caudal and cell nest regions in the squirrel also correspond to the regions in the cat where la muscle and other deep modalities were reported to have a major input [Rosen.…”

Section: Discussionmentioning

confidence: 55%

“…1980], The present report de scribes the distribution of cervical dorsal root fibers to the tree squirrel DCN and adjacent nuclei. Attention was given spe cifically to the relationship between the organization of ascending root fibers, their terminal patterns and the somatic and modality organization of the DCN in the squirrel [Ostapoff et al, 1982] and other animals.…”

Section: Introductionmentioning

confidence: 99%

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The Projection of Cervical Primary Fibers to the DCN of the Squirrel, <i>Sciurus niger: </i>Fiber Sorting in the Dorsal Columns

1983

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The course and terminal distribution of cervical primary afferents in the dorsal column nuclei were studied in the fox squirrel, Sciurus niger. Unilateral rhizotomies were performed at cervical levels C₃, C₄, C₅, C₆ and C₈. For all spinal levels studied except C₈, degeneration in the medullary cuneate fasciculus was present within two distinct groups. They included a large oblique lateral lamina and a small superficial group of degeneration. The superficial group was horizontal, located medial to the large lamina and appeared to be formed by the medial shifting of fibers away from the initial larger group. Fibers in the large primary lamina appeared to terminate primarily in the ventrolateral areas of the cuneate nucleus. Fibers from the superficial group, however, appeared to project mostly to dorsal cuneate nuclear areas. Hence, the dual transverse terminal patterns for cervical fibers in the cuneate nucleus appeared to be related directly to a fiber sorting process that involved the formation of two often separate ascending fiber groups in the cuneate fasciculus. The results of this study are compared with the mechanosensory mapping of the dorsal column nuclei in the squirrel.

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Section: Discussionmentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

The Projection of Cervical Primary Fibers to the DCN of the Squirrel, <i>Sciurus niger: </i>Fiber Sorting in the Dorsal Columns

1983

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“…In addition, it is likely that nearly all of the labeled terminations in the gracile nuclei of the present experiments belonged to the functional classes of slowly (SA) and rapidly (RA) adapting afferents that subserve the skin of monkeys and other mammals. While responses of neurons to deep receptor (muscle spindle) stimulation have been reported for neurons in the region of the gracile nuclei (Ostapoff et al, 1983), these were neurons in rostral locations that likely correspond to deep receptor nuclei for the hindlimb (nucleus Z; Landgren and Silfvenius, 1971) that complement the external cuneate nucleus with muscle spindle receptor inputs from the forelimb (Abrahams and Swett, 1986). Such deep and cutaneous afferents are mixed in the lumber levels of the gracile fasciculus, but they sort out so that only cutaneous mechanoreceptors are represented at cervical levels of the gracile fasciculus (Whitsel et al, 1969(Whitsel et al, , 1972.…”

Section: Functional Implications Of the Anatomical Organization Of Thmentioning

confidence: 97%

“…Projections from the tail were located in the extreme medial region of the gracile nucleus, followed laterally by a region with inputs from the heel, a still more lateral region for the knee, and a hip region occupying the extreme lateral portion of the nucleus. In fox squirrels, Ostapoff et al (1983) stressed the dorsoventral organization of the gracile nucleus, as recordings along vertical electrode penetrations encountered neurons successively responsive to the tail, foot, leg, and trunk. In opossums, recordings from the gracile nucleus revealed that the foot is represented lateral to that of the tail, and dorsal to that of the leg, but few additional details were reported (Hamilton and Johnson, 1973).…”

Section: Gracile Nuclei Of Other Mammalsmentioning

confidence: 99%

Organization of primary afferent projections to the gracile nucleus of the dorsal column system of primates

Kaas

2006

J of Comparative Neurology

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In order to reveal the somatotopic organization of the gracile nucleus of the dorsal column-trigeminal complex, neuroanatomical tracers were injected subcutaneously into various parts of the hindlimb and tail of prosimian galagos, New World monkeys, and Old World monkeys. In most cases, tracers were injected bilaterally, and into more than one body part. In six cases, two different, distinguishable tracers were injected into the same hindlimb. Brainstem and spinal cord sections were processed for tracers transported by cutaneous afferents to terminations in the gracile nuclei. Foci of terminations were related to the cell-cluster architecture of the gracile nuclei in sections processed for cytochrome oxidase or stained for cell bodies (Nissl stain). In all taxa, terminations labeled by the injections were distributed in a patchy fashion along the rostrocaudal length of the ipsilateral gracile nucleus. Terminations were largely but not completely focused within the cytochrome oxidase dense cell clusters. Across taxa, afferents from the tail, foot, lower leg, and upper leg terminated in a mediolateral sequence within the gracile nucleus. Afferents from the glabrous skin of toes 1-5 terminated in a ventromedial to dorsolateral sequence in owl, squirrel, and macaque monkeys, but an altered arrangement was seen in the galagos, with a ventrolateral location for toe 1. The use of two tracers in squirrel monkeys indicated that terminations from adjacent toes formed adjacent and largely segregated patches. Terminations of afferents from the plantar pad (sole) of the foot tended to surround those from the glabrous toes.

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“…Within the DCN, used here to include nucleus gracilis (GN), nucleus cuneatus (CN), and external cuneate nucleus (EC), these fibers are now known to reach particular nuclei, subnuclei, andor areas within subnuclei based on their somatotopic origins (Campbell et al, 1974;Johnson et al, 1968;Kruger et al, 1961) and, to a lesser extent, on their modalities (Blum et al, 1975;Dykes et al, 1982;Millar and Basbaum, 1975;Ostapoff et al, 1983). With the background provided by these studies of somatotopy and modality sorting in several mammalian species, it is possible to examine the distribution of dorsal root fibers to the DCN in any species and to draw limited conclusions about the locations and relative densities of classes of receptors in skin vs. muscle supplied by that particular root.…”

Section: Introductionmentioning

confidence: 99%

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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Mechanosensory projections to cuneate, gracile, and external cuneate nuclei in a tree squirrel (fox squirrel, Sciurus Niger)

Cited by 24 publications

References 21 publications

The Projection of Cervical Primary Fibers to the DCN of the Squirrel, <i>Sciurus niger: </i>Fiber Sorting in the Dorsal Columns

The Projection of Cervical Primary Fibers to the DCN of the Squirrel, <i>Sciurus niger: </i>Fiber Sorting in the Dorsal Columns

Organization of primary afferent projections to the gracile nucleus of the dorsal column system of primates

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

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