Lateral Cervical Nucleus Research Articles

Ascending somatosensory projections to the medial accessory portion of the inferior olive: a retrograde study in cats.

The cells in the dorsal column nuclei, lumbosacral spinal cord, lateral cervical nucleus, and nucleus z that project to the medial accessory portion of the inferior olive of cats were identified with retrograde tracing techniques. Injections of wheat germ agglutinin complexed to horseradish peroxidase were made in the caudal portion of the medial accessory olive, either (1) involving no portion of the dorsal accessory olive or (2) involving in addition the caudal tip of the dorsal accessory olive. The tissue was processed with tetramethyl benzidine. The locations of all relay neurons were compared with those of dorsal accessory olive projection neurons, as described in a previous study (Molinari, '84a). Localized populations of neurons gave rise to most of the projection to the medial accessory olive. These neurons were found in the peripheral portions of the dorsal column nuclei caudal to the obex and in the ventromedial ventral horn of the entire lumbosacral enlargement. Few projection neurons were found in the lateral cervical nucleus and none in the nucleus z. Neurons in the peripheral dorsal column nuclei and ventromedial ventral horn were labeled by injections in either the medial or dorsal accessory olives. Following medial accessory olive injections, however, they constituted the only labeled somatosensory neurons, while following dorsal accessory olive injections they represented only a small fraction of the labeled neurons. Based on their locations, it is proposed that these neurons might be the source for both the medial and dorsal accessory olives of information signalling movement of the proximal limb. Such a proposal is consistent with functional descriptions of the medial and dorsal accessory olives and the cerebellar anterior lobe.

Somatotopic termination of spinal afferents to the feline lateral cervical nucleus.

The labelling pattern of the feline lateral cervical nucleus (LCN) was investigated after pressure injections of lectin-conjugated horseradish peroxidase into cervical, thoracic or lumbar segments of the spinal cord. Sixteen cats received a 5-8 nl injection staining large parts of mainly the ipsilateral grey matter of a single segment. Light microscopic examination of frozen sections reacted with tetramethylbenzidine showed a somatotopic organization in the LCN. Rostral segments of the spinal cord projected mainly to rostroventral and medial parts of the ipsilateral LCN, while more caudally located segments projected to more dorsocaudal and lateral parts of the nucleus. Minor contralateral labelling with a similar somatotopic arrangement was seen in animals given cervical and lumbar injections. No significant labelling was found in the LCN of three control animals, the segmental injections of which were engaged mainly into the ipsilateral dorsal columns and the dorsolateral funiculus. Ultrastructural analysis in two animals which received multiple cervical or lumbar injections showed that about 70% of the peroxidase-positive structures in the LCN were boutons and the rest small myelinated axons. The precise termination pattern of ascending afferents to the LCN is compatible with the somatotopic organization of the other relay centres in the spino-cervico-thalamic pathway.

Red nucleus modulation of somatosensory responses of cat spinal cord dorsal horn neurons

Single unit extracellular recordings were obtained from cat lumbar spinal cord dorsal horn activated by cutaneous inputs The effect of electrical conditioning stimuli applied to the red nucleus (RN) was predominantly that of inhibition although in some cases excitation was seen. All the neurons that projected to the lateral cervical nucleus were inhibited; none of these were excited. These findings suggest that the RN may exert a dynamic modulatory action on the transmission of cutaneous information during the execution of a motor program.

Endogenous peroxidase-like activity in the feline dorsal column nuclei and spinal cord.

Endogenous peroxidase-like activity was investigated with a combined light and electron microscopical technique in 15 cats. The lateral cervical nucleus, the dorsal column nuclei, and segments C6 and L5 of the spinal cord were incubated with diaminobenzidine-tetrahydrochloride (DAB) or tetramethylbenzidine (TMB). After histochemical reaction with DAB a considerable amount of activity was found in nerve cells, astrocytes and pericytes. The neuronal labelling was mainly located in mitochondria of axon terminals and in dendrites whereas the astrocytic and pericytic activity was found in cytoplasmic dense bodies. The quantity of stained structures differed considerably between the animals. In TMB reacted tissue endogenous peroxidase-like activity was only sparsely seen. It was found mainly in frozen sections, in which the neuropil and perivascular structures sometimes contained granules and irregular filaments. The significance of the findings is discussed in relation to observations in tracer studies using horseradish peroxidase.

Ascending somatosensory projections to the dorsal accessory olive: an anatomical study in cats.

The cells in the gracile nucleus that project to the dorsal accessory olive were identified in cats with retrograde tracing techniques. In the same animals, the retrograde labeling patterns in the lateral cervical nucleus and the lumbosacral spinal cord were also examined. Small injections of wheat germ agglutinin complexed to horseradish peroxidase were made in the ventrolateral portion of the dorsal accessory olive without involving the medial accessory olive and without damaging the medial lemniscus. The tissue was processed with tetramethyl benzidine. In each of the three relay nuclei, the neurons that project to the ventrolateral portion of the contralateral dorsal accessory olive are highly concentrated in small regions. In the gracile nucleus these cells are found almost exclusively in the transitional zone, just caudal to the obex and rostral to the clusters. In the lateral cervical nucleus they are concentrated in the dorsolateral tip. In the lumbosacral spinal cord in segments L5 and L6 the cells are found primarily in lamina V, while in segments L7 and S1 they are found along the ventromedial edge of the ventral horn. In the gracile and lateral cervical nuclei there is no segregation of neurons that project to the rostral and caudal portions of the dorsal accessory olive. Comparison of these results with physiological data suggests that each of the three sources of ascending somatic input conveys some distinct aspect of sensory information from the hindlimb to the dorsal accessory olive.

Brainstem influences on transmission of somatosensory information in the spinocervicothalamic pathway

The inhibition of somatosensory responses of lateral cervical nucleus neurons resulting from stimulation of the brainstem has been investigated. Single unit extracellular recordings were obtained from neurons in the lateral cervical nucleus of chloralose-anesthetized cats. Electrical stimulation of the periaqueductal gray, nucleus raphe magnus, nucleus cuneiformis, and nuclei reticularis gigantocellularis and magnocellularis was found to be very effective in inhibiting the responses of lateral cervical nucleus neurons evoked by electrical or tactile stimulation of the skin. Additional experiments were performed to determine whether the inhibitory effects were mediated in the spinal cord dorsal horn or in the lateral cervical nucleus. These experiments which examined the effect of brainstem stimulation on the responses induced by stimulation of the dorsolateral funiculus or on the antidromic latency of activation of lateral cervical nucleus neurons from thalamus, revealed that most and possibly all the inhibition could be accounted for by an action on the spinal cord. These results are consistent with other studies showing that spinocervical tract cells in the spinal cord can be inhibited by stimulation of the same brainstem regions.

Anatomical Studies of the Spinocervical Tract of the Rat

The retrograde transport of horseradish peroxidase (HRP) was used to identify and examine the cells of origin of the spinocervical tract (SCt) in the rat. Initially, precise data on the boundaries of the rat lateral cervical nucleus (LCn) were gathered after injecting HRP into the ventrobasal thalamus. These data indicated that the LCn of the rat is restricted to a region on the extreme lateral edge of the dorsalmost portion of the lateral funiculus (DLf) within spinal segment C2. Following small iontophoretic injections of HRP that were restricted to this area, labeled SCt neurons were found in the ipsilateral nucleus proprius at all levels of the spinal cord but were most numerous in the cervical enlargement. Lesion studies indicated that the overwhelming majority of SCt axons ascend to the LCn within the DLf. In an attempt to determine whether our injection techniques labeled a significant number of cells through axons of passage, HRP injections were made in the DLf ventral to the LCn. Such injections labeled, presumably through axons of passage, cells in several areas of the spinal cord gray matter, including a large number in the contralateral marginal zone. Injections in areas immediately rostral to the LCn labeled 20% or less of the total number of cells within the enlargements that were labeled by injections into the LCn. Thus, the majority of cells labeled by injections of HRP into the LCn were labeled through preterminal fibers or terminals themselves. The cells of origin of the SCt in the rat are similar in location to those in the cat but far fewer in number.

Immunocytochemical studies of the lateral cervical and lateral spinal nuclei

Immunocytochemical studies of the lateral cervical and lateral spinal nuclei

Spatial relationships between the terminations of somatic sensory motor pathways in the rostral brainstem of cats and monkeys. II. Cerebellar projections compared with those of the ascending somatic sensory pathways in lateral diencephalon.

Previous studies have shown that ascending somatic sensory pathways arising from the dorsal column nuclei, lateral cervical nucleus and spinothalamic tract terminate in parts of the thalamus adjacent to those which receive cerebellar terminations. This termination pattern creates a border between the ventroposterolateral nucleus (VPL) and the ventrolateral nucleus (VL) in the cat and between the caudal and oral parts of VPL (VPLc and VPLo, respectively) in the monkey. Since it is not clear how sharp these borders are, a double orthograde labeling strategy was used in the present study to make direct comparisons of the projections to the thalamus from these sources of input. It was found that there was a change in the sources of afferent input to the different target areas that paralleled changes in cytoarchitecture. Moving caudally to rostrally, VPL in the cat and VPLc in the monkey received projections predominantly from the middle, dorsal (clusters) portion of the dorsal column nuclei. These projections were gradually replaced near the VPL-VL border in the cat and VPLc-VPLo border in the monkey first by input from the lateral cervical nucleus (cat only) and the rostral and ventral portions of the dorsal column nuclei and then by spinothalamic projections. Towards VL in the cat and the rostral parts of VPLo in the monkey (referred to as Vim by Hassler, '59 and Mehler, '71), these projections were in turn replaced by those from the cerebellum. This sequence resulted in a complex pattern (summarized in Fig. 10) where some thalamic territories received input predominantly from one source and others received converging input from several sources. The major region receiving converging ascending somatic sensory and cerebellar terminations was located at the border between VPL and VL in the cat and in the caudal parts of Olszewski's ('52) VPLo in the monkey (that is, between VPLc and Vim). In general, the results in the cat were similar to those in the monkey. One notable difference was that the domain containing terminals from the cerebellum and the rostral-ventral parts of the dorsal column nuclei was located medially between VPLc and Vim in the monkey, whereas it extended across the entire mediolateral border between VPL and VL in the cat. In both species, thalamic neurons received input predominantly from one afferent source and only minor input, if any, from other sources.(ABSTRACT TRUNCATED AT 400 WORDS)

The termination in the mesencephalon of fibres from the lateral cervical nucleus. An anatomical study in the cat

The termination in the dorsal mesencephalon of fibres from the lateral cervical nucleus (LCN), recently discovered with the retrograde tracing technique, was investigated by both the degeneration method and anterograde transport of lectin-conjugated horseradish peroxidase. Both strategies gave similar results. The termination area was found to be situated at the level of transition between the superior and inferior colliculi and comprises mainly the intercollicular nucleus and the deep and intermediate layers of the posterolateral pole of the superior colliculus. The functional implication of the demonstrated projection from LCN is discussed in relation to somatosensory activity in the mesencephalic tectum.

Sensitization of unmyelinated nociceptive afferents in monkey varies with skin type.

Sensitization of unmyelinated nociceptive afferents in monkey varies with skin type.

The origin of the spinomesencephalic tract in the rat: an anatomical study using the retrograde transport of horseradish peroxidase.

An anatomical technique based on the retrograde transport of horseradish peroxidase (HRP) was used to investigate the projections of spinal cord neurons to the mesencephalic tegmentum in the rat. Restricted unilateral injections were confined to central grey, cuneiformis areas, and superior colliculus. Injections into all these loci produced labeling in similar spinal areas. Only quantitative differences were noted. In the spinal grey matter, numerous labeled cells were regularly encountered in the marginal zone, the lateral part of the neck of the dorsal horn, and the dorsal grey commissure. Projections from the marginal zone and neck of the dorsal horn were predominantly contralateral. In the white matter, a pronounced bilateral labeling was observed in the nucleus of the dorsolateral funiculus, thus confirming our previous electrophysiological findings (Menétrey et al., '80). This distribution of labeled cells was commonly observed throughout the whole length of the cord. Additional sites of projecting cells have also been identified at the most rostral levels (obex, C1, C2). They mostly derived from spinal extensions of the dorsal column nuclei and lateral cervical nucleus contralaterally; from the lateral ventral horns bilaterally and from the nucleus commissuralis ipsilaterally. This study is thus a clear confirmation that the mesencephalic tegmentum constitutes a target for various somatosensory inputs originating from spinal cord, dorsal column nuclei, and lateral cervical nucleus. Moreover, from these results together with those obtained for the spinothalamic tract in the rat, it appears that marginal and dorsolateral funiculus neurons preferentially project to the mesencephalic tegmentum. The importance of marginal zone projections underlines the involvement of the spinomesencephalic tract in pain mechanisms.

Dorsolateral spinal afferents to some medullary sensory nuclei. An anatomical study in the cat.

The course and termination of afferents in the spinal dorsolateral fascicle to some medullary sensory nuclei were studied by tracing degeneration following lesions of spinal white matter. The main conclusions depend on successive degeneration experiments; other points were studied with single-stage lesions. The dorsal column nuclei were particularly studied; terminations in these nuclei following dorsolateral lesions followed a clear-cut pattern, with fibres arising from segments below T6 terminating in the gracile nucleus and those with more rostral origin solely in the cuneate nucleus. In both nuclei, the major terminations were in their rostral third with most fibres traversing deep caudal regions where some termination also occurred. Some fibres ended contralaterally. These restricted regions of termination contrasted with the wide-spread terminations seen after lesions of the dorsal column. A region at the cuneate rostral pole, adjacent to but clearly separable from nucleus z, receives a dense projection from both caudal and rostral spinal levels, the former fibres terminating in the dorsal part of the region, the latter extending more ventrally. We treat this as a separate subnucleus. The afferents to the dorsal column (together with those terminating in the other nuclei studied) were confined to the extreme dorsolateral white matter. Our observations confirm the established view that only afferents arising from caudal segments (below at least T 4-5) terminate in nucleus z, and that afferents terminating in group x arise from all levels (at least between C5 and L5): also that neither receives any afferents through the dorsal columns. Dorsolateral fibres arising from segments above at least T6 terminate in a clear-cut area at the lateral border of the external cuneate nucleus. Heavy terminal degeneration was also seen in the lateral cervical nucleus of afferents arising from both above and below T 4-5.

Organization of somatosensory input to the deep collicular laminae in hamster

Retrograde transport of horseradish peroxidase (HRP) was used to delineate the sources of somatosensory input to the hamster's superior colliculus. Cells in the ipsilateral somatosensory cortex and contralateral dorsal horn of the spinal cord, dorsal column nuclei, lateral cervical nucleus, internal basilar nucleus, nucleus of the spinal trigeminal tract and deep layers of the superior colliculus were labeled following HRP injections centered in the deep tectal laminae. The response characteristics of somatosensory corticotectal, spinotectal and intertectal neurons were investigated with extracellular single unit recording methods and, with the exception of the fact that the receptive fields of corticotectal and spinotectal neurons were consistently smaller than those of cells recorded in the colliculus, the response characteristics of these neurons were quite similar to those of somatosensory neurons in the deep layers of the tectum. Lesions of the somatosensory cortex or dorsal half of the spinal cord were also combined with single unit recording in the colliculus to determine whether or not such damage altered the incidence and/or response characteristics of deep layer somatosensory cells. These lesions had no appreciable effect upon the functional organization of the deep tectal laminae. The implications of these results with regard to the convergence of visual and somatosensory information in the tectum are discussed.

Cortical and spinal somatosensory input to the superior colliculus in the golden hamster: an anatomical and electrophysiological study.

The horseradish peroxidase technique was used to identify the sources of somatosensory afferent fibers to the hamster superior colliculus. These experiments demonstrated that the tectum receives axons from pyramidal cells in layer V of the ipsilateral sensorimotor cortex, contralateral lamina IV of all levels of the spinal cord, the contralateral dorsal column nuclei, lateral cervical nucleus, internal basilar nucleus, and nucleus of the spinal trigeminal tract. Electrical stimulation of the spinal cord coupled with extracellular single unit recordings concentrated, for the most part, in the posterior portion of the tectum revealed that such stimuli activated approximately 40% of the cells tested. Almost all of these units were isolated ventral to the stratum opticum and 86% were responsive only to somatosensory stimulation. Analysis of the latencies of collicular responses obtained with two point spinal stimulation in intact hamsters and in animals subjected to somatosensory cortical and/or spinal damage indicated that the initial impulse elicited from most collicular cells was mediated by a polysynaptic pathway(s) which probably synapses in the dorsal column, lateral cervical, and/or internal basilar nuclei. Damage to the dorsal spinal cord and/or somatosensory cortex altered neither the incidence nor the response characteristics of spinally driven collicular neurons. This indicated that most somatosensory collicular cells also received input from the spinotectal fibers which travel in the ventrolateral quadrant. Electrical stimulation of somatosensory cortex activated about 20% of the cells tested in the ipsilateral superior colliculus. If cortical and spinal stimulation were delivered with an interstimulus interval ranging between 50 and 80 msec the response of the tectal neuron to the latter stimulus was suppressed in most cases. This was true regardless of the order of the stimulus pairing. Concurrent somatosensory cortical shocks also suppressed responses to tactile stimuli for 21% of the cells tested.

Differences in the collateralization of neuronal projections from the dorsal column nuclei and lateral cervical nucleus to the thalamus and tectum in the cat: An anatomical study using two different double-labeling techniques

The dorsal column nuclei (DCN) and the lateral cervical nucleus (LCN) project to the diencephalon and tectum. In order to determine which neurons project to these targets and whether any of them have collateral projections, the double-retrograde labeling techniques developed by Hayes and Rustioni 17 and Kuypers et al. 22 were used. Both strategies produced similar results. Within DCN, neurons which projected to the diencephalon were located differently and had a different morphology than those which projected to the tectum. The diencephalic-projecting neurons, which were preferentially located within the middle part of the DCN complex were mainly large (> 15 μm diameter) and round. The tectal-projecting neurons, often located along the edges of the gracile and cuneate nuclei or between them, were most often found outside of the middle parts of the DCN complex (i.e. predominantly rostrally and frequently also caudally). These tectal-projecting neurons varied in size and were usually oval or fusiform in shape. In contrast to DCN, neurons in LCN which projected either to the tectum or diencephalon did not differ morphologically and in both groups were of various sizes and shapes. They were intermixed haphazardly, predominantly within the lateral two-thirds of the nucleus. In addition, another class of neurons, constituting more than 40% of the labeled population in some experiments, had collateral projections to both terminal targets. These double-labeled neurons were haphazardly mixed with other labeled neurons. These results demonstrate differences in the divergence patterns of DCN and LCN neurons. Considering these anatomical results together with the electrophysiological results of other investigators, it appears likely that DCN neurons which have different projections may also have different functional properties. The evidence for LCN neurons, however, is not consistent with such a suggestion.

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.

Corticofugal actions on the lateral cervical nucleus of the cat

The question of possible corticofugal actions on the lateral cervical nucleus (LCN) of the cat was reinvestigated. Recordings were made from single relay cells, identified histologically as lying in the LCN which was deafferented by spinal cord lesions to avoid interference from corticospinal-cervical pathways. Intracortical stimulation of the contralateral sensorimotor cortex inhibited all 53 cells studied, but in addition excited only 25% of them (mean latency 5 ms). Cortical stimulation also inhibited mass transmission through the LCN. Care was taken to avoid inhibition due to stimulating high-threshold receptors in the head. Exploration with the stimulating electrode of large parts of the cerebral cortex allowed lowest threshold (45 to 90 μA; 10 ms train of cortical shocks of 1 ms duration at 500 Hz) zones for inhibition of the LCN to be located, but no low-threshold zones for excitation could be found. (Indirect current spread with such stimulation of the cortex was shown to be about 1.5 mm.) Histological reconstruction of the stimulating tracks showed that the low-threshold zone was cylindrical, rostrally, lying in the grey matter of that part of the cytoarchitectural area 3a which represents the face. Caudally, the low-threshold zone was in white matter where the corticofugal pathway would be expected to course. Such a nonsomatotopically organized inhibitory pathway is unusual in sensory systems and suggests that the LCN may be involved in certain tasks requiring face-limb coordination.

The density, distribution and topographical organization of spinocervical tract neurones in the cat.

1. In acute experiments, detailed grids of micro-electrode recordings were made from spinocervical tract (s.c.t.) cells in the lumbosacral cord of anaesthetized cats. These grids provided electrophysiological data on the location, distribution, density and somatotopic organization of s.c.t. neurones.2. In acute experiments lasting up to 48 hr, retrograde labelling of s.c.t. cells was carried out by injecting horseradish peroxidase into the lateral cervical nucleus in anaesthetized cats. The aim was to flood the nucleus with the enzyme so that all s.c.t. neurones would be labelled in order to provide an independent check on the location, density and distribution data obtained in the electrophysiological experiments.3. The electrophysiological and the anatomical experiments were sometimes performed on the same animal.4. The electrophysiological and anatomical results were in excellent agreement. (a) S.c.t. cells are located mainly in ipsilateral laminae III, IV and V. About 25% are in lamina III, 60% in lamina IV and 10% in lamina V. There are a few cells in laminae I, II and VI making up the remaining 5%. (b) There are about 550-800 s.c.t. cells in the lumbosacral enlargement (L4-S2 inclusive) on each side of the cord. Most cells are in L7-S1 where there are twenty to forty s.c.t. neurones in each millimetre length of cord.5. Many marginal (lamina I) cells were labelled with the retrograde horseradish peroxidase method and a few cells on the contralateral side in laminae III-V and VII-VIII were also labelled. The marginal cells formed 12-18% of labelled cells on the side of injection and, in addition, a similar absolute number of marginal cells was labelled on the side contralateral to the injection. The possible identity of these neurones is discussed.6. S.c.t. cells form a sheet of neurones across the dorsal horn. The sheet is organized somatotopically in a way which resembles the representation of the hind limb dermatomes in the dorsal columns (Werner & Whitsel, 1967). There is a relative enlargement of the L6-S1 dermatomes which encroach upon their neighbouring cord segments. The gradient of the map is very steep in the mediolateral direction but gradual in the rostrocaudal direction. The detailed somatotopic maps generated in the present work have revealed that s.c.t. cells are arranged so that their receptive fields form longitudinal columns and cells within the columns have overlapping fields.

An HRP study of the afferents to the inferior olive in cat. I. -- Cervical spinal and dorsal column nuclei projections.

Localization of the cell bodies of the fibers of the direct spino-olivary pathways as well as those laying in the dorsal column nuclei and the nucleus cervicalis lateralis as the indirect pathway, have been studied using horseradish peroxidase injected in the inferior olive. The injection sites were both large, involving no less than one third of the antero-posterior extent of the inferior olive, and small, involving less than one third. Labeling of the spinal cord was never found beyond the TI segment even after a seven day survival time. Significant positive reaction was found only in the upper cervical levels contralaterally in the lamina VI and bilaterally in the border regions of laminae VII, VIII and IX. Few marked neurons were found in the contralateral nucleus cervicalis lateralis. More numerous labelled cells were found in the dorsal column nuclei, gracilis and cuneatus. Although positive reactions were observed bilaterally, it was far more important in the contralateral side. The topographical relationship between the dorsal column nuclei and the inferior olive is also described.