The lateral cervical nucleus of the Japanese monkey (Macaca fuscata)

The Historical Evolution of Topographical Mapping and Nomenclature of the Lateral Cervical and Lateral Spinal Nuclei

The intricate organization of nuclei within the dorsolateral funiculus of the spinal cord has long been an area of interest in the field of neuroanatomy. Numerous researchers have endeavored to determine the morphology, neurochemistry, connections, and physiology of the lateral cervical nucleus and lateral spinal nucleus throughout history. This manuscript charts the historical progression in the mapping, naming, and comprehension of the lateral cervical nucleus and lateral spinal nucleus across a variety of species, such as rats, mice, marmosets, rhesus monkeys, and humans. It synthesizes significant research spanning decades, which together shed light on the nuanced topography of these nuclei, starting from Theodor Ziehen's foundational work in 1903, through Molander's precise mappings, to the detailed contemporary mappings by modern scholars. Despite the wealth of research elucidating the mappings of these nuclei, there remains a need for further investigation into their roles and neurochemical characteristics.

The tracts, cytoarchitecture, and neurochemistry of the spinal cord

The human spinal cord can be described using a range of nomenclatures with each providing insight into its structure and function. Here we have comprehensively reviewed the key literature detailing the general structure, configuration of tracts, the cytoarchitecture of Rexed's laminae, and the neurochemistry at the spinal segmental level. The purpose of this review is to detail current anatomical understanding of how the spinal cord is structured and to aid researchers in identifying gaps in the literature that need to be studied to improve our knowledge of the spinal cord which in turn will improve the potential of therapeutic intervention for disorders of the spinal cord.

Comparative Gross Anatomy of the Forelimb Arteries of the Japanese Monkey (Macaca fuscata) and a Comparative Pattern of Forelimb Arterial Distribution in Primates

Macaca fuscata displays characteristic behaviours, such as stone handling, locomotor behaviour, gait position, and intermittent bipedalism. Differences in characteristic behaviours among primate species/genera could be explained by anatomical details of the body. However, the anatomical details have not been well studied in Macaca fuscata. Arterial models could be one of the anatomical bases for the phylogenetic and functional differences among species, since the arterial supply could be associated with the muscular performance, especially locomotor behaviour. In this study, five thoracic limbs of Macaca fuscata adults were dissected to analyse the vessels. Patterns of arterial distribution in the thoracic limbs of Macaca fuscata were compared with those in other primates. The results indicated that the arterial distribution in the Japanese monkeys was more similar to those in Macaca mulatta and Papio anubis, which is consistent with phylogenetic similarities. However, compared with Papio anubis and other macaques, there were anatomical differences in several points, including (1) the origin of the common, anterior, posterior circumflex, and profunda brachii, and (2) the origins of the collateralis ulnaris artery. The comparative anatomy of the arteries in the forelimb of Macaca fuscata, along with the anatomical studies in other primates, indicated characteristic patterns of brachial artery division and the number of the palmar arches in primates, which is consistent with the phylogenetic division among New World primates, Old World primates, and apes.

The sensory neurons of touch

The somatosensory system decodes a wide range of tactile stimuli and thus endows us with a remarkable capacity for object recognition, texture discrimination, sensory-motor feedback and social exchange. The first step leading to perception of innocuous touch is activation of cutaneous sensory neurons called low-threshold mechanoreceptors (LTMRs). Here, we review the properties and functions of LTMRs, emphasizing the unique tuning properties of LTMR subtypes and the organizational logic of their peripheral and central axonal projections. We discuss the spinal cord neurophysiological representation of complex mechanical forces acting upon the skin and current views of how tactile information is processed and conveyed from the spinal cord to the brain. An integrative model in which ensembles of impulses arising from physiologically distinct LTMRs are integrated and processed in somatotopically aligned mechanosensory columns of the spinal cord dorsal horn underlies the nervous system's enormous capacity for perceiving the richness of the tactile world.

A systematic review of spinal fMRI research: outlining the elements of experimental design

Object

Since the first published report of spinal functional MRI (fMRI) in humans in 1996, this body of literature has grown substantially. In the present article, the authors systematically review all spinal fMRI studies conducted in healthy individuals with a focus on the different motor and sensory paradigms used and the results acquired.

Methods

The authors conducted a systematic search of MEDLINE for literature published from 1990 through November 2011 reporting on stimulation paradigms used to assess spinal fMRI scans in healthy individuals.

Results

They identified 19 peer-reviewed studies from 1996 to the present in which a combination of different spinal fMRI methods were used to investigate the spinal cord in healthy individuals. Eight of the studies used a motor stimulation paradigm, 10 used a sensory stimulation paradigm, and 1 compared motor and sensory stimulation paradigms.

Conclusions

Despite differences in the results of various studies, even when similar stimulation paradigms were used, this body of literature underscores that spinal fMRI signals can be obtained from the human spinal cord. The authors intend this review to serve as an introduction to spinal fMRI research and what it may offer the field of spinal cord injury research.

Neuroanatomy of the pain system and of the pathways that modulate pain

We review many of the recent findings concerning mechanisms and pathways for pain and its modulation, emphasizing sensitization and the modulation of nociceptors and of dorsal horn nociceptive neurons. We describe the organization of several ascending nociceptive pathways, including the spinothalamic, spinomesencephalic, spinoreticular, spinolimbic, spinocervical, and postsynaptic dorsal column pathways in some detail and discuss nociceptive processing in the thalamus and cerebral cortex. Structures involved in the descending analgesia systems, including the periaqueductal gray, locus ceruleus, and parabrachial area, nucleus raphe magnus, reticular formation, anterior pretectal nucleus, thalamus and cerebral cortex, and several components of the limbic system are described and the pathways and neurotransmitters utilized are mentioned. Finally, we speculate on possible fruitful lines of research that might lead to improvements in therapy for pain.

Thalamically projecting cells of the lateral cervical nucleus in monkey

The number, location, and morphology of thalamically projecting lateral cervical nucleus (LCN) cells were determined in monkey using retrograde transport of wheatgerm agglutinin-conjugated horseradish peroxidase. These data were compared to the total population of LCN neurons as determined by Nissl stain. In 4 Macaca fascicularis and one Saimiri sciureus the average size of the thalamic projection from LCN was found to be 506 +/- 94 cells contralateral to the injections. Thalamically projecting LCN neurons were located between the lower medulla and the third cervical segment; approximately 90% of these cells were in the first two cervical segments. Morphologic analysis of thalamically projecting LCN cells showed that they were smaller in size, and more oblong in shape in caudal regions of the nucleus. In 3 macaques, the average total number of LCN cells was determined to be 1617 +/- 908 on one side, in Nissl material. In these Nissl-stained preparations LCN neurons were found as far caudal as the fourth cervical segment; 68% were located in the first two cervical segments. Hence, thalamically projecting LCN neurons in the monkey are located in the rostral portion of the nucleus and comprise about one-third of the total population. Comparison of these data with reports in the literature imply that, unlike the cat, the major projection from LCN in monkeys is to the mesencephalon rather than to the thalamus.

GABA-immunoreactive neurons and terminals in the lateral cervical nucleus of the cynomolgus monkey

An antiserum against the inhibitory transmitter substance gamma-aminobutyric acid (GABA) was used to investigate the distribution of GABAergic nerve terminals and cell bodies in the lateral cervical nucleus (LCN) of the cynomolgus monkey. Light microscopic immunohistochemistry demonstrated GABA-immunoreactive puncta, suggestive of nerve terminals, scattered throughout the LCN. The terminal-like profiles are often present along the somata of unlabeled neurons, but most are located in the neuropil. GABA-immunoreactive neurons are present in the LCN, but constitute a very small number of the LCN neurons. Electron microscopy showed that the GABA-positive neurons are small with a relatively large nucleus. They are contacted by few somatic boutons. Numerous GABA-immunoreactive terminals containing densely packed round to oval synaptic vesicles were also found. Most GABA-positive terminals make synaptic contact with dendrites, but synapses with cell bodies are also present. Synaptic contacts between labeled and unlabeled terminals were not observed. Some GABA-positive terminals make contact with GABA-positive neurons. The present findings suggest that GABA is a major inhibitory transmitter substance in the LCN of the monkey. However, in comparison with other somatosensory relay nuclei, there are few GABA-immunoreactive neurons in the LCN. This may imply that the GABA-positive neurons branch extensively in the LCN or that an extrinsic source of GABAergic input exists.

Organization of anterogradely labeled spinocervical tract terminations in the lateral cervical nucleus of the cat

The anterograde transport of horseradish peroxidase following injections into the cervical, thoracic, or lumbosacral spinal cord was used to examine the organization of spinocervical tract terminations in the lateral cervical nucleus (LCN) of the cat. A somatotopic organization of the labeling originating from different spinal levels was observed in the mediolateral dimension. Cervical labeling generally occurred in the ventromedial portion and lumbosacral labeling in the dorsolateral portion of the LCN. Thoracic labeling occurred both in the middle and the most lateral edge of the nucleus. In all cases, labeling was distributed over most of the rostrocaudal extent of the LCN. In addition, distinct patches of labeling were present in the medialmost portion of the nucleus, regardless of the spinal level injected. These observations corroborate the topographical organization of the LCN described previously on the basis of physiological and retrograde labeling data, and support the identification of the medialmost part of the LCN as a distinct portion of the nucleus. Terminal labeling in the LCN always occurred in multiple, longitudinally distributed fields. The afferent input to each terminal field coursed in separate, loose bundles of fibers that descended from the superficial dorsolateral funiculus. Large injections resulted in more extensive, overlapping terminal fields. These observations indicate that collateral projections result in several discrete representations of a given portion of the skin over the longitudinal extent of the LCN, but that topographical relationships are longitudinally maintained. It is suggested that these multiple terminal fields are the anatomical correlate of the functionally selective convergence of spinocervical tract terminations, that has previously been postulated on physiological grounds to explain the generation of LCN receptive fields with homogenous receptor input within a somatotopic framework.

Evidence for the existence of a lateral cervical nucleus in mice, guinea pigs, and rabbits

The lateral cervical nucleus of carnivores is large and is thought to play a prominent role in somatosensory processing. In contrast, early studies indicated that rats, mice, guinea pigs, and rabbits did not have a lateral cervical nucleus. However, we reported the existence of a lateral cervical nucleus in rats as a result of studies using retrograde transport techniques. In the present study, similar techniques were used to examine the possibility that early studies also overlooked the lateral cervical nucleus in mice, guinea pigs, and rabbits. In each of these species, a retrograde tracer was injected into the thalamus. These injections labeled a small number of neurons contralaterally in the dorsal part of the lateral funiculi of rostral cervical segments. Mice had the greatest number of neurons projecting from the lateral cervical nucleus to the thalamus, and rabbits had the fewest.

Thalamic projections from lateral cervical nucleus in monkey. A degeneration study

The projection from the lateral cervical nucleus (LCN) to the thalamus has been investigated in macaque monkeys. After electrolytic lesions of the LCN, the degeneration was studied in sections impregnated by the Wiitanen method. The cervicothalamic fibers cross the midline at their level of origin and ascend to the thalamus in the medial lemniscus. A small ipsilateral projection may also exist. The tract terminates in the posteromedial (POm) and ventralis posterolateralis (VPL) nuclei. Termination in the POm is indicated by the presence of a small number of thin preterminal fibers. In the VPL the cervicothalamic fibers are unevenly distributed, forming patches of moderately dense preterminal networks, mainly in the medial two-thirds of the nucleus. Rostrocaudally the termination is restricted to areas corresponding to Olszewski's VPLc. Compared to cat, the cervicothalamic projection to the VPL in the monkey appears considerably smaller. It is also much smaller than the spinothalamic projection to the VPL in the monkey. The results neither confirm nor exclude a small projection to the nucleus ventralis posteromedialis (VPM) from the lateral cervical nucleus.

The lateral cervical nucleus in the cat: anatomic organization of cervicothalamic neurons

The morphology of the lateral cervical nucleus (LCN) and the organization of the cervicothalamic projection neurons were studied in cats which had received thalamic injections of horseradish peroxidase (HRP). The boundaries of the LCN were defined following very large thalamic (HRP injections. Roughly 92-97% of LCN cells project contralaterally to thalamus; an additional 1.5% project ipsillaterally. Computer-assisted measurements of perikaryal areas demonstrated that there are two sizes of LCN cells, large (175-900 micrometer 2) and small (less than 175 micrometer 2); the small cells are localized in the medial third of the LCN. LCN cells which are not labeled after large thalamic HRP injections are predomininantly small, medially-located neurons. Small HRP injections into physiologically identified regions of ventroposterior thalamus demonstrated that cervicothalamic neurons are organized in a topography consistent with that observed physiologically in the LCN (Craig and Tapper, '78). Dorsolateral LCN cells are retrogradely labeled from nucleus ventroposterolateralis, pars lateralis (VPL1), ventromedial LCN cells are labeled from pars medialis (VPL m), and a few medial cells are labeled from nucleus ventroposteromedialis (VPM). A few cells in the medial portion of the LCN are also labeled from each part of ventroposterior thalamus. Some interspersion was observed even in the cases with the most well-restricted labeling. We conclude that the LCN maintains a basic somatotographic organization with an inherent variability, certain aspects of which are consistently demonstrable both physiologically and anatomically. Evidence was also obtained suggestive of a rostrocaudal inversion in the cervicothalamic projection. The cervicothalamic projection, the differentiation of the medial LCN subpopulation, and the possible redefinition of the LCN are discussed in light of these results.

Spinal and medullary input to the lateral cervical nucleus

The distributions of spinal and medullary cells projecting to the lateral cervical nucleus (LCN) have been investigated in young cats and dogs using the retrograde horseradish peroxidase (HRP) technique. Labeled spinal cells, whose axons contribute to the spinocervical tract (SCT), were found at all levels of the spinal cord ipsilateral to the injection sites. No significant differences were found between cat and dog, nor between cases with single injections at different levels of the LCN. SCT cells were found predominantly, if not exclusively, within lamina IV, with some extension into medial lamina V. No apparent mediolateral or dorsoventral density gradient was observed within lamina IV; cells of all sizes were labeled. Cells in cervical laminae I and V-VII were occasionally labeled; these, however, were considered to be propriospinal, supplying afferent fibers to the C1-2 dorsal horn. Cells of origin of spinocerebellar fibers consistently remained unlabeled in cases with restricted HRP injections and minimal fiber damage in the dorsolateral funiculus (DLF) around the injection sites. These results, therefore, corroborate and refine the findings of electrophysiological studies of the SCT and the LCN. Labeled medullary cells were located in the caudoventral and rostral portions of the dorsal column nuclei (DCN; stellate and fusiform cells), the underlying n. medullae oblongatae centralis, subnucleus dorsalis (parvicellular medullary reticular formation), the marginal and magnocellular layers (both large and small cells) of the n. trigeminalis spinalis pars caudalis and also in pars interpolaris; a cluster of cells was also consistently labeled in the lateral reticular formation just ventral to pars caudalis. The projection from the DCN to the LCN was confirmed with the anterograde Nauta technique. Fiber degeneration was observed in the entire ipsilateral LCN, although it was less abundant than that observed in the adjacent C1-2 dorsal horn. These results indicate that neurons in the rostral portions of the DCN not only may affect the input to the LCN (at the level of the dorsal horn), but also the output of the LCN itself. These data also suggest the possibility of both noxious and non-noxious facial input to the LCN.

The ascending projections of the dorsolateral funiculus of the spinal cord in the primate

The ascending projections of the dorsolateral funiculus of the spinal cord to the brain stem have been determined in five macaque monkeys. Connections to the lateral cervical nucleus and to the reticular nucleus of the cord in the C1 and C2 segments are present. In the medulla the most prominent connections are to the nuclei "Z" and "x" of Brodal and Pompeiano, to the rostral portion of n. gracilis and to the n. proprius of the restiform body. Minor projections reach the rostral part of the medial and lateral cuneate nuclei, the reticular nucleus, the n. centralis dorsalis and the periependymal gray. There were no projections to planes rostral to the medulla. In view of the connections established it is concluded that ascending systems in the DLF to the brain stem of primates are concerned with transmission of mechanoreceptor input to the cerebellum and thalamus and that nociceptive relay appears very unlikely.

Spinal pathways projecting to the cerebral first somatosensory area in the monkey

1. Potentials evoked with short latency in the cerebral post-central gyrus after intradermal electrical, or adequate light tactile stimulation of the contralateral body half have been studied in the monkey, before and after transection of different spinal pathways at the upper cervical level.2. Initially, positive potentials evoked by both types of stimulus were recorded after transection of the dorsal funiculi with the same somatotopic, topographical distribution as before the lesion.3. The potentials recorded after transection of the dorsal funiculi could be evoked via one pathway located in the dorsal half of the lateral funiculus ipsilateral to the afferent input, and another pathway located, at least partially, in the ventral funiculus contralateral to the afferent input.4. Of these two pathways, the crossed ventral pathway was found necessary to keep the topographical distribution of the evoked potentials unaltered.