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B C Albright

Publications and source records attributed to B C Albright.

11 recordsLinked to original sources
PubMed1988

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

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.

Afferent Pathways↗
PubMed1984

Morphologic evidence for fiber sorting in the fasciculus cuneatus.

This report describes the medullary course and projection patterns of cervical dorsal root nerve fibers in five mammalian species (bushbaby, tree squirrel, raccoon, potoroo, and brush-tailed possum). After cutting a single cervical dorsal root and allowing appropriate postoperative survival, we studied serial, Fink-Heimer impregnated sections of the medulla from each individual to locate degenerated afferent fibers and endings. Fibers from those rostral (C2) or caudal (C8) cervical roots studied traverse the medulla as a single bundle, forming collaterals en route into the nucleus cuneatus and external cuneate nucleus at all levels. Fibers from most cervical roots (C4 through C7, sometimes C3), however, separate into two discrete bundles as they project rostrally. A more medial, superficially placed group of fibers projects predominately to the dorsal part of nucleus cuneatus, which seems to be somatotopically arranged. The second fiber group, larger, deeper, and more laterally situated, projects mainly to ventral and ventrolateral nucleus cuneatus (asomatotopically) and to the external cuneate nucleus. Based on segmental and species differences in the presence of this fiber separation, and on prior physiologic and anatomic evidence, we suggest that this form of fiber sorting in the cuneate fasciculus is modality based. It appears likely that fibers in the medial group are of primarily cutaneous origin, and that many if not most of those in the larger lateral population arise from deep receptors in muscle and joints.

Afferent Pathways↗
PubMed1983

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

The distribution and organization of mechanosensory projections to the cuneate, gracile and external cuneate nuclei were mapped in tree squirrels anesthetized with ketamine and urethane. Tungsten microelectrodes were used to record unit and unit cluster responses to mechanical stimulation. Most responses in the gracile nucleus were to stimulation of skin and hairs of the tail, hind foot and leg, and trunk, in that order going from dorsal to ventral in the nucleus. A similar distribution of responses was found in the cuneate nucleus to stimulation of forelimb, neck and pinna going from dorsomedial to ventrolateral in the nucleus. Some responses to stimulation or movement of subcutaneous tissue were found in the cuneate and gracile nuclei. Responses in the external cuneate were to stimulation of deep-lying tissues in the hand medially, the lower arm centrally and the shoulder and trunk laterally. The pattern of projections in the tree squirrel differed most strikingly from that seen in raccoons and opossums in the relatively small extent of projections from the glabrous skin of the forepaws which were concentrated in a small region near the obex in squirrels. In contrast, there was a large representation of hairy receptive fields located on the forelimb in all regions of the squirrel cuneate nucleus. Otherwise, the somatotopic organization of mechanosensory projections to these dorsal column nuclei in tree squirrels was similar to that reported in other mammals.

Afferent Pathways↗
PubMed1983

The projection of cervical primary fibers to the DCN of the squirrel, Sciurus niger: fiber sorting in the dorsal columns.

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.

Animals↗
PubMed1983

Synaptic arrangements in the ventral posterolateral nucleus of the squirrel.

Because murine rodents have no complex synaptic arrangements in the ventral posterolateral nucleus (VPL), we sought to determine if the lack of complexity was a characteristic common to all rodents. We studied the synaptology of VPL in the fox squirrel, Sciurus niger, using electron microscopy. We found vesicle-containing dendrites and complex synaptic arrangements in the squirrel VPL. Therefore, the relative simplicity of the rat and mouse VPL is not a general feature of the rodent somatosensory thalamus.

Animals↗
PubMed1982

The distribution of lateral funicular and cortical fibers to the dorsal column, Z and X nuclei in the prosimian Galago.

The distribution of lateral funicular and cerebral corticofugal fibers to the dorsal column, Z and X nuclei were studied in the prosimian primate Galago senegalensis. Lesions of the lateral funiculus resulted in a differential distribution pattern of preterminal degeneration within the nuclei studied. In the nucleus gracilis, spinal lesions produced moderate amounts of debris in ventral cell nest and rostral areas. Diffuse degeneration was present in both the dorsal cell nest area of the nucleus gracilis and the rostral nucleus cuneatus. Extremely dense debris was present within both ipsilateral Z and X nuclei. Cortical ablations of predominantly hind-limb motor-sensory areas resulted in degeneration throughout most of the longitudinal and transverse extent of the contralateral dorsal column nuclei. Degeneration appeared to be more concentrated in ventral nuclear areas. The distribution of cortical fibers to the rostral gracile and Z nuclei was essentially the inverse of that observed for lateral funicular fibers. The contralateral nucleus Z received only a sparse corticobulbar input while the rostral gracile contained more moderate amounts of preterminal degeneration. The results are in agreement with previous reports on the morphology and fiber connections of the dorsal column, Z and X nuclei in Galago and other animals. They support the concept that the Z and X nuclei are functional components of the dorsal column nuclear system.

Afferent Pathways↗
PubMed1978

Dorsal column nuclei in a prosimian primate (Galago senegalensis). II. Cuneate and lateral cuneate nuclei: morphology and primary afferent fibers from cervical and upper thoracic spinal segments.

The morphology and brachial cord primary afferent projections of the cuneate and lateral cuneate nuclei have been studied in the lesser bushbaby. The cuneate nucleus was divided into three regions. From caudal to rostral these were the large cell, cell column and rostral regions. Primary afferents from C2, C4, C6, C7, C8, T1 and T3 terminated within distinct partially overlapping terminal zones in the ipsilateral large cell and cell column regions of the cuneate nucleus (CN) and the lateral cuneate nucleus (LCN). Segmentotopic was the greatest in the rostal region of the CN due to a more diffuse projection pattern. In the LCN, the transverse terminal fields appeared as curved mediolaterally oriented laminae. In each case, ascending fibers of passage from C4, C6, and C7 in the cuneate fasciculus were organized so that two distinct fiber laminae were present. The separation of fibers and the formation of the two ascending laminae were completed either within two segments rostral to their respective level of entry (for C6 and C7 lesions) or in the caudal medulla (for C4 lesion). For each of these segments, the laminae consisted of a small dorsomedial one and a large lateral one. The organization of primary afferents from one segment into two ascending fiber laminae in the cuneate fasciculus was reflected in a differential termination pattern within both the CN and LCN. The results of this study were discussed relative to earlier anatomical and physiological studies on the DCN in other animals.

Afferent Pathways↗
PubMed1975

Dorsal root afferents to clarke's column from hindlimb cord levels in Tupaia and Galago.

The projection of hindlimb dorsal root afferents to Clarke's column has been studied in the tree shrew (Tupaia glis) and lesser bushbaby (Galago senegalensis). In the bushbaby, fibers from K12, L1 and L3 projected ipsilaterally to Clark's nucleus from levels L3 to T3, L2 to T4 and L3 to T5 respectively. In Tupaia, afferents from T11, L1, and L3 terminated ipsilaterally within the nucleus from segments L2 to T4, L3 to T6, and L3 to T8. Fibers from T12, L1, and L3 in Galago and T11 in Tupaia terminated within the even to lateral aspect of the nucleus at lower levels, throughout the nucleus at middle levels and in the dorsal aspect of the column at rostral levels. Fibers from T11 and L1 have a similar ventrolateral pattern of termination in lower levels, however, at rostral levels preterminal debris was present throughout the width of the nucleus. Fibers from L1 and L3 in the bushbaby form a complex longitudinal network with the medullary region of the nucleus in segments T11 to T8. Afferents from levels T5 in Tupaia and L6 in Galago projected ipsilaterally to the nucleus from level L3 to T10, and T8, respectively. Fibers from these segments terminated throughout the extent of the column at L3 and, rostrally projected to more dorsal regions of the nucleus. In this study, fibers from S2, and S3 and CCO2 did not terminate in Clark's column. Both the segmental distribution of hindlimb dorsal root fibers and their pattern of termination in Clark's nucleus in the tree shrew were similar to that reported in quadrupedal primates and other quadrupedal mammalian forms. The results of this study were interpreted as evidence which relates the complex organization of the Clark column system in the lesser bushbaby to its vertical clinging and leaping style of locomotion.

Animals↗