The Projection of Cervical Primary Fibers to the DCN of the Squirrel, &lt;i&gt;Sciurus niger: &lt;/i&gt;Fiber Sorting in the Dorsal Columns

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

doi:10.1159/000121512

Cited by 5 publications

(1 citation statement)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our results on the pattern of projections of the auditory nerve to the CN are in good agreement with the earlier reports showing degenerating fibers in dorsal and ventral cochlear nuclei (Cohen et al, 1972, Kane, 1974, Albright et al, 1983, Kim et al, 2004a, Kim et al, 2004c, b, Feng et al, 2012). The decrease in SV2-labeled presynaptic terminals in the VCP compared to control animals also supports the interpretation that this silver staining protocol is in fact labeling degenerating auditory nerve fibers and terminals.…”

Section: Discussionsupporting

confidence: 93%

Effects of acoustic trauma on the auditory system of the rat: The role of microglia

Baizer

Wong

Manohar³

et al. 2015

Neuroscience

View full text Add to dashboard Cite

Exposure to loud, prolonged sounds (acoustic trauma, AT) leads to the death of both inner and outer hair cells (IHCs and OHCs), death of neurons of the spiral ganglion and degeneration of the auditory nerve. The auditory nerve (8cn) projects to the three subdivisions of the cochlear nuclei (CN), the dorsal cochlear nucleus (DC) and the anterior (VCA) and posterior (VCP) subdivisions of the ventral cochlear nucleus. There is both anatomical and physiological evidence for plastic reorganization in the denervated CN after AT. Anatomical findings show axonal sprouting and synaptogenesis; physiologically there is an increase in spontaneous activity suggesting reorganization of circuitry. The mechanisms underlying this plasticity are not understood. Recent data suggest that activated microglia may have a role in facilitating plastic reorganization in addition to removing trauma-induced debris. In order to investigate the roles of activated microglia in the CN subsequent to acoustic trauma we exposed animals to bilateral noise sufficient to cause massive hair cell death. We studied four groups of animals at different survival times: 30 days, 60 days, 6 months and 9 months. We used silver staining to examine the time course and pattern of auditory nerve degeneration, and immunohistochemistry to label activated microglia in the denervated CN. We found both degenerating auditory nerve fibers and activated microglia in the CN at 30 and 60 days and 6 months after AT. There was close geographic overlap between the degenerating fibers and activated microglia, consistent with a scavenger role for activated microglia. At the longest survival time, there were still silver-stained fibers but very little staining of activated microglia in overlapping regions. There were, however, activated microglia in the surrounding brainstem and cerebellar white matter.

show abstract

Section: Discussionsupporting

confidence: 93%

Effects of acoustic trauma on the auditory system of the rat: The role of microglia

Baizer

Wong

Manohar³

et al. 2015

Neuroscience

View full text Add to dashboard Cite

show abstract

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

Culberson

1987

Am. J. Anat.

View full text Add to dashboard Cite

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.

show abstract

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

View full text Add to dashboard Cite

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.

show abstract

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

Cited by 5 publications

References 11 publications

Effects of acoustic trauma on the auditory system of the rat: The role of microglia

Effects of acoustic trauma on the auditory system of the rat: The role of microglia

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

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

Contact Info

Product

Resources

About