Lateralis Dorsalis Research Articles

Spinal control of pelvic floor muscles

A prevalent notion in the literature is that the pelvic floor muscles behave as a unitary mass. We examined this proposition experimentally. In spinal cats, we recorded EMG activity from the following pelvic floor muscles: the sphincter ani externus (SAE), the abductor caudae internus (coccygeus), and the levator ani (pubiocaudalis) muscles. The epaxial sacrocaudalis dorsalis lateralis muscle was also exposed and prepared for recording. Electrical stimulation of S2 ventral roots elicited twitch responses of the sphincter ani externus and of the sacrocaudalis dorsalis lateralis muscles. Stimulation of S3 and Cx1 ventral roots elicited responses in the other two muscles studied, the levator ani and abductor caudae internus. Thus a clear segregation of the segmental motor neuron pools innervating the different pelvic floor muscles was demonstrated. The various muscles of the pelvic floor region could be reflexly activated either individually or as a mass unit depending on the intensity of stimulation. Tactile or electrical stimulation of pudendal regions on either side of the body elicited responses of the sphincter ani externus. In contrast, activation of the levator ani and abductor caudae internus muscles could be lateralized: tactile or electrical stimulation of the dorsolateral surfaces at the base of the tail region elicited ipsilateral responses from these muscles. Section of one pudendal nerve did not alter the level of tonic activity (2 to 4s) of the sphincter ani externus. However, bilateral section of the pudendal nerve entirely abolished both tonic activity and phasic responsiveness of the SAE without affecting the activity of the levator ani and abductor caudae internus muscles. Pudendal nerve stimulation elicited only polysynaptic reflex responses from S2 ventral roots. The results presented show that the neural apparatus of the striated musculature of the pelvic floor is capable of activating individually the different muscles that make up the system, and that the sphincter ani externus from one side, and muscles that conform the diaphragm pelvis from the other, are subserved by different neuronal circuits.

Anolis johnmeyeri Wilson and McCranie: Additional Specimens and a New Locality

During field work in Honduras in August of 1982, we collected a second female specimen from the type locality and two males of the species from a new locality. The topotypic female (KU 192623) was collected on 3 August along the same section of stream as the holotype at 1560 m. The specimen was collected in late morning as it moved about on the ground at the base of a tree. Two adult males of A. johnmeyeri (KU 1926245) were collected on 9 and 10 August, respectively, at an approximate elevation of 1400 m in cutover cloud forest just above the village of Quebrada Grande (15?05'N, 88?55'W), located at the base of Cerro Azul, a mountain peak in the southern part of the Sierra de Omoa in the western portion of the department of Copan. The anoles came from fallen tree trunks in a cattle pasture. This locality is about 85 airline km southwest of the type locality. The Cusuco female agrees very well with the description of the holotype and the males have the appearance one would expect of males of this species. Together they confirm the distinctiveness of A. johnmeyeri from other members of the schiedei group. The color in life of one of the males (KU 192624) was as follows: dorsum pale brown with creamoutlined brown blotches along and on either side of the dorsal midline; head and limbs yellowish tan, latter with dark-outlined cream-colored bands; tail yellowish tan with cream-outlined brown bands; venter pale yellowish tan; iris rust red; dewlap red-orange with large central royal blue spot, scales across middle pale yellow, those of periphery yellow. In the same male, the ventral scales are smooth, imbricate, and number 43 between axilla and groin. The lateral dorsals are minute and unicarinate. The scales of the paravertebral rows are enlarged, forming a ridge, several times the size of the lateral dorsal scales, and number 55 between axilla and groin. The number of ventrals and enlarged dorsals in a head length are 39 and 40, respectively. The scales around midbody number 144. The scales in the prefrontal and frontal areas are keeled and convex; some frontonasal scales are tricarinate, others unicarinate and rugose. There is a prominent prefrontal cavity, six scales between the nasal scales and one between each nasal and rostral scale. Five scales border the ros-

Distribution of 5-hydroxytryptamine (serotonin) in the brain of the teleost Gasterosteus aculeatus L.

The distributions of serotoninergic neurons in the brain of the three-spined stickleback was demonstrated with the indirect peroxidase-antiperoxidase (PAP) immunohistochemical method with antibodies against serotonin. Serotoninergic perikarya were demonstrated in the brainstem reticular formation (nucleus raphe dorsalis, nucleus raphe medialis, and nucleus tegmenti dorsalis lateralis) and in the periventricular ventral thalamus and hypothalamus (nucleus ventromedialis thalami, nucleus posterioris periventricularis, nucleus recessus lateralis, and nucleus recessus posterioris). After pharmacological pretreatment of the animals with a monoamine oxidase inhibitor, serotoninergic perikarya were also visualized in area praetectalis and in the medial brainstem, caudal to nucleus raphe medialis. Whereas the cell groups of the brainstem give rise to both ascending and descending pathways, it was not possible to analyze the distribution of efferent projections from the diencephalic cell groups. Distribution of serotoninergic axons showed marked regional differences. Only scattered varicose fibers were demonstrated in the cerebellum, the facial lobes, and the lateral line lobes. In the mesencephalon, the dorsal periventricular tegmentum and the central gray receive only small numbers of serotoninergic axons, while torus semicircularis and the visual layers of tectum opticum are profusely innervated. In the diencephalon, the hypothalamus and ventral thalamus generally display the highest density of serotoninergic axons. Exceptions are found in nucleus glomerulosus and the ventromedial portion of lobus inferioris, where densities are low. In the telencephalon, the density of serotoninergic axons is very high in area dorsalis pars medialis and pars lateralis dorsalis, but low in area dorsalis pars dorsalis and pars lateralis ventralis, and intermediate in area ventralis.

An immunocytochemical study of the serotonergic innervation of the thalamus of the rat.

The serotonergic innervation of the rat thalamus was studied with an indirect immunocytochemical technique using an antiserum raised against a serotonin-hemocyanin conjugate in animals pretreated with L-tryptophan and a monoamine oxidase (MAO) inhibitor. When pretreatment was not used there was a decrease in the number of immunoreactive fibers observed in the thalamic region. Innervation was greatest in nucleus ventralis corporis geniculati lateralis, and in the following midline nuclei: nucleus periventricularis, nucleus rhomboideus, and nucleus reuniens. Also well labeled were nucleus anterior ventralis, the intralaminar nuclei, and nucleus lateralis dorsalis. Moderate innervation was found in nucleus reticularis, nucleus anterior dorsalis, nucleus ventralis medialis, nucleus lateralis pars posterior, the posterior complex, and in nucleus dorsalis corporis geniculati lateralis. Very few serotonergic fibers were observed in nucleus paratenialis, nucleus gelatinosus, nucleus anterior medialis, nucleus medialis dorsalis, nucleus ventralis, nucleus ventralis pars dorsomedialis, or in nucleus corporis geniculati medialis. Serotonin immunoreactivity was also noted in a number of fiber bundles in the thalamic region. These include the fasciculus retroflexus, the fasciculus mamillothalamicus, the stria medullaris, and the stria terminalis. These results differ from those of previous descriptions of the serotonergic innervation of thalamic nuclei most notably in the midline nuclei and in the posterior complex. In this study the midline nuclei, nucleus rhomboideus, and nucleus reuniens were more densely innervated than had been described, and in the posterior complex a moderate, rather than sparse, innervation was observed. The more densely innervated nuclei of the anterior and lateral nuclear groups, nucleus lateralis dorsalis and nucleus anterior ventralis, also contained a greater number of labeled fibers than had been indicated.

Long descending projections of the hypothalamus in the pigeon, Columba livia.

An autoradiographic analysis was performed on the descending projections of nucleus periventricularis magnocellularis (PVM) of the hypothalamus in the pigeon. A PVM-medullospinal pathway was observed coursing posteriorly through the lateral hypothalamus, ventrolateral midbrain tegmentum, and into the spinal lemniscus (ls) in the ventrolateral pons and medulla. In the pons, some fibers course dorsomedially from ls and terminate at the lateral border of the locus coeruleus. At medullary levels, fibers from ls sweep dorsomedially in the plexus of Horsley and project to certain regions of the nucleus of the solitary tract (NTS) and the dorsal motor nucleus of the vagus (NX). Specifically, PVM fibers project heavily into NTS subnuclei medialis superficialis, medialis ventralis, and lateralis (sulcalis) dorsalis as well as into the ventral parvocellular subnucleus of NX. Fibers in ls were traced caudally into the lateral funiculus as far as upper cervical levels of the spinal cord. Although autoradiographs of lower cervical or thoracic spinal cord sections were not available, PVM fibers do descend to thoracic spinal cord levels, as evidenced by the retrograde transport of horseradish peroxidase. In addition to the medullospinal pathway, the autoradiographs demonstrated PVM projections to septum, diencephalon, and midbrain. Labeled PVM fibers are found in the lateral septal nucleus, nucleus of the anterior pallial commisure, dorsomedial thalamic nucleus, dorsolateral anterior thalamic nucleus (pars ventralis), median eminence, medial and lateral hypothalamus, medial mammillary area, and nucleus intercollicularis and central gray of the midbrain. The projection of fibers to medullospinal regions and median eminence suggests that PVM is homologous to the mammalian paraventricular nucleus. These projections to specific subnuclei of NTS and NX denote hypothalamic control over certain autonomic functions.

Subcortical projections to the occipital and parietal lobes of the chimpanzee brain.

The subcortical sources of afferents to occipital and parietal cortex were studied in two chimpanzees with the aid of retrogradely transported horseradish peroxidase (HRP). In chimpanzee 1, HRP was injected into right cortical areas 17 and 18; chimpanzee 2 received HRP into right areas 17, 18, 19, and 39. The following subcortical structures were found to project to area 17 and/or area 18: locus coeruleus, dorsal raphe nucleus, nucleus annularis, nucleus centralis superior, pontine reticular formation, mesencephalic reticular formation, dorsal hypothalamus, lateral hypothalamus, nucleus basalis of Meynert, nucleus of the diagonal band of Broca, claustrum, nucleus basalis lateralis amygdalae, lateral geniculate nucleus, inferior pulvinar, lateral pulvinar, nucleus limitans, medial magnocellular part of the nucleus ventralis anterior, nucleus paracentralis, and nucleus centralis medialis thalami. Some of these structures may also project to area 19 and/or area 39. The following thalamic nuclei were found to project to area 19 and/or area 39 but not to areas 17 and 18: nucleus lateralis posterior, nucleus centralis lateralis, nucleus medialis dorsalis, nucleus ventralis lateralis, nucleus ventralis anterior nucleus lateralis dorsalis, and nucleus anterior ventralis. In several Instances, the HRP-labeled cells traversed specific nuclear borders, extending uninterruptedly from one classically defined nucleus into another. These results in the chimpanzee largely confirm data from a number of other mammalian taxa on the subcortical sources of afferents to the posterior cortex. Because of the close biological relationship between chimpanzee and man, we feel confident that such projections are also features of the human brain.

The distribution of corticotropin releasing factor-like immunoreactive neurons in rat brain

Using the indirect immunofluorescent technique, corticotropin releasing factor (CRF)-like immunoreactive nerve fibers and cell bodies were observed to be widely distributed in rat brain. A detailed stereotaxic atlas of CRF-like immunoreactive neurons was prepared. Large numbers of CRF-containing perikarya were observed in the nucleus paraventricularis, with scattered cells in the following nuclei: accumbens, interstitialis stria terminalis, preopticus medialis, supraopticus, periventricularis hypothalami, amygdaloideus centralis, dorsomedialis, substantia grisea centralis, parabrachialis dorsalis and ventralis, tegmenti dorsalis lateralis, vestibularis medialis, tractus solitarius and reticularis lateralis. The most intense staining of CRF-containing fibers was observed in the external lamina of the median eminence. Moderate numbers of CRF-like fibers were observed in the following nuclei: lateralis and medialis septi, tractus diagonalis, interstitialis stria terminalis, preopticus medialis, supraopticus, periventricularis thalami and hypothalami, paraventricularis, anterior ventralis and medialis thalami, rhomboideus, amygdaloideus centralis, habenulae lateralis, dorsomedialis, ventromedialis, substantia grisea centralis, cuneiformis, parabrachialis dorsalis and ventralis, tegmenti dorsalis lateralis, cerebellum, vestibularis medialis, reticularis lateralis, substantia gelatinosa trigemini and lamina I and II of the dorsal horn of the spinal cord. The present findings suggest that a CRF-like peptide may be involved in a neurotransmitter or neuromodulator role, as well as a hypophysiotropic role.

On the organization of the retino-tecto-thalamo-telencephalic pathways in a Chilean rodent; the Octodon degus

After performing eye enucleations or restricted lesions in the superior colliculus or the pulvinar nucleus, the degeneration patterns provoked by these procedures were analyzed by means of the Nissl and the Fink-Heimer methods in 30 specimens of Octodon degus. The pulvinar or lateroposterior nucleus can be subdivided into 3 regions (rostrolateral, rostromedial and caudal), on the basis of cytoarchitecture, tectofugal afferent and efferent connections to the cerebral cortex. In addition, this nucleus projects to the ipsilateral tail of the caudate nucleus and to the nucleus lateralis dorsalis of the thalamus, which has been shown to project over the cingulate cortex in this animal. These findings support the possibility that the pulvinar may have an important role in visuo-limbic interactions, by way of its connections with the nucleus lateralis dorsalis. Another highly interesting finding from the phylogenetic point of view is that the organization of the pulvinar in the Octodon degus is remarkably similar to that organization of the retino-tecto-thalamo-cortical pathways described in the grey squirrel and in the tree shrew is strikingly similar to those found in the Octodon degus, a semi-fossorial South American rodent that has evolved in isolation from the two former species for about 40 million years, makes it impossible to explain the organization of this pathway by advocating convergent evolution, due to environmental pressures determined by arboreal life, as postulated by Kaas et al. 39.

Unit responses of intralaminar thalamus to midbrain and medullary stimulation and effects of conditioning caudate and hippocampal stimuli

Single units responding to heterotopic somatic stimuli, on extracellular recording in thalamic intralaminar and neighbouring nuclei, also responded to stimulation of the midbrain tegmentum or the medullary magnocellular reticular formation. Consideration of response latencies suggested that some monosynaptic projections from both midbrain and medulla may be received in nuclei centralis lateralis, centrum medianum-parafascicularis complex, and medial ventralis lateralis. Responses to brainstem of nuclei medialis dorsalis, lateralis dorsalis, and lateralis posterior were of considerably longer latency. There was no correlation between shortness of latency and following-rate of unit responses; the ability of intralaminar neurones to follow rapidly-repeated brainstem stimuli is inferred to be limited by inhibitory processes rather than by synaptic interruptions in the afferent pathway. Conditioning stimuli to caudate nucleus or hippocampus suppressed most intralaminar responses to midbrain stimuli, the shortest-latency responses included, suggesting that inhibitory effects could be exerted at the thalamic level, perhaps directly on the responsive neurone.

Visuo-limbic interactions: Evidence for a pathway from the pulvinar to the cingulate cortex

Synaptic-terminal degeneration was analyzed in 18 specimens of Octodon degus after stereotaxic lesions in the pulvinar nucleus. Aside from the cortical targets of the pulvinar (Kuljis et al. 1979), a conspicuous projection towards the nucleus lateralis dorsalis of the thalamus (LD) was observed. The LD is known to receive fibers from the fornix (Valenstein and Nauta 1959), and to project heavily over the cingulate cortex (Locke et al. 1964; Ajmone Marsan 1965; Graybiel 1974); we have confirmed the latter projection in 3 operated specimens of Octodon degus. The possibility is discussed, in the light of these findings, that the pulvino-LD pathway may be important for the purposes of visuo-limbic interactions.

Neurochemical identification of cholinergic forebrain projection sites of the nucleus tegmentalis dorsalis lateralis

The projection sites of the nucleus tegmentalis dorsalis lateralis (ntdl) were examined in rats by a biochemical technique. The ntdl was destroyed unilaterally and brains were assayed after 14 days survival for changes in choline acetyltransferase activity in discrete brain areas. A bilateral projection appears to exist to the anteroventral and the posterior nucleus of the thalamus. An ipsilateral projection to the lateral portion of the medial thalamic nucleus and the ventral geniculate was found. It is suggested that the nucleus tegmentalis dorsalis lateralis may play a role in the modulation forebrain areas.

Organization of extrinsic tectal connections in Goldfish (Caraccius auratus).

Nonretinal sources of tectal afferents, the laminar and regional organization of the inputs, and the relation of the tectum with primary and secondary visual and motor centers in goldfish were studied following HRP injections in the optic tectum, orbit of the eye, cerebellum, pretectal area, and dorsolateral mesencephalic tegmentum. Ipsilateral tectal afferents include the area dorsalis centralis of the forebrain, the nucleus dorsalis lateralis of the thalamus, the area pretectalis, the nucleus pretectalis, a nucleus in the rostral mesencephalic tegmentum, the torus longitudinales, the torus semicircularis, a dorsolateral tegmental nucleus, the nucleus isthmi, and a rostral cell group of the nucleus motorius tegmenti. Comparison of results in a series of tectal HRP injections which differed in depth, tangential extent, and location indicated that projections from the area pretectalis, nucleus pretectalis, and nucleus isthmi terminate in the stratum fibrosum et griseum superficiale of the tectum. Terminals of the forebrain and nucleus dorsolateralis and contralateral tectum are sparse and widely branching. Projections from the area and nucleus pretectalis tend to terminate in the rostral tectum, and those from the contralateral tectum, torus semicircularis, dorsolateral tegmental nucleus, and nucleus motorius tegmenti terminate preferentially in the caudal tectum. Cells of origin of extrinsic tectal efferents were also identified following HRP injections in the pretectal area and mesencephalic tegmentum. Proximal dendrites and axons of these cells were labeled sufficiently to allow comparison with morphological types characterized in Golgi studies. HRP injections in the cerebellum labeled cells bodies in the area pretectalis, nucleus pretectalis, and the nucleus of the posterior commissure. Double label experiments with intraocular injection of tritiated proline demonstrated direct retinal input to these three areas. No indications of direct connections between the tectum and cerebellum were found following tectal or cerebellar HRP injections.

Maturation of thalamic inputs into the associative cortical areas during postnatal ontogenesis in cats.

Thalamic afferents into the sensorimotor and parietal cortex (area 7) were studied using the method of retrograde axonal transport of horseradish peroxidase (HRP) in kittens of three age groups. Following HRP injection into the sensorimotor cortex of 1- to 3-day-old kittens, labeled cells were found in the following nuclei: ventral posterolateral (VPL), ventral posteromedial (VPM), medialis dorsalis (MD), centrum medianum (CM), and centralis lateralis (CL). In 9- to 10-day-old kittens the number of labeled cells and density of reaction product within the cells was found to increase markedly. In 21- to 30-day-old kittens, besides the above-mentioned nuclei, labeled cells were also revealed in n. ventralis lateralis (VL). A similar trend was seen following HRP injections into area 7. In 1- to 3-day-old kittens, labeled cells were found in n. lateralis posterior (LP), in n. ventralis anterior (VA), and in Pulvinar (Pulv). Both in the 9- to 10-day-old and the 21- to 30-day-old kittens, labeled cells were also demonstrated in n. lateralis dorsalis (LD) and CL. For both of the cortical areas the number of labeled cells and the density of labeling within the cells increase during postnatal ontogenesis. This may be attributed to the growing number of axon terminals. In general, our results suggest that differences in the thalamic connections of single cortical areas can be distinguished during the postnatal ontogenesis of the brain.

Histochemical identification and afferent connections of subdivisions in the lateralis posterior-pulvinar complex and related thalamic nuclei in the cat

Fiber pathways of the extrageniculate visual system have been shown in the cat to define an orderly sequence of adjoining, roughly parallel zones within the posterolateral thalamus. The present study provides evidence that these and related thalamic subdivisions can be identified histochemically by their differing contents of acetylthiocholinesterase. The brains of fifty cats were prepared for acetylthiocholinesterase histochemistry by the methods of Geneser-Jensen & Blackstad and Karnovsky & Roots. Serial sections were cut in each of the three Horsley-Clarke planes and a standard transverse cholinesterase series, containing occasional reference sections stained for myelin or Nissl substance, was used to assemble graphic reconstructions of the main cholinesterase subdivisions. Patterns of afferent connections were visualized by anterograde axon transport or fiber-degeneration techniques and recorded in thirteen sets of detailed chartings. In nine sets, serially adjoining sections processed by the cholinesterase and anterograde methods were directly compared and plotted together. The caudal part of the lateral thalamic region was divided into two main subdivisions: the lateralis posterior-pulvinar complex, which receives extrageniculate visual input, and the complex comprising the nuclei lateralis medialis and suprageniculatus (LM-Sg), which receives fiber projections from auditory association cortex and the deep layers of the superior colliculus. The latter complex occupies a ventromedial zone alongside the lateralis posterior-pulvinar complex. It is distinguished in the cholinesterase stain by prominent 0.5–1.5 mm wide patches of high enzyme activity that appear against a pale background. Within the lateralis posterior-pulvinar complex, three zones could be distinguished: (1) the medial part of the nucleus lateralis posterior (LPm) is rich in cholinesterase activity and receives input from the superficial collicular layers; (2) the lateral part of the nucleus lateralis posterior and the nucleus posterior of Rioch (LP1-NP) have much weaker cholinesterase activity and receive input from the striate cortex and other areas of visual cortex; (3) the pulvinar, the most lateral of the subdivisions, is a zone of high cholinesterase activity in which some pale patches appear. It receives input from the pretectum and is associated with a differentiated lateral marginal zone receiving direct projections from the retina and area 17. The intermediate nucleus of the lateral group was divided into two parts. The pars caudalis (LIc) has a mottled appearance in the cholinesterase stain; it receives an ascending input from the pretectotectal border zone and a descending projection from parietal cortex including area 7. The pars oralis of the intermediate nucleus (LIo) is rich in cholinesterase activity; it receives a descending projection from the anterior parietal cortex comprising in part area 5. These two intermediate subdivisions were flanked dorsally and rostrally by the nucleus lateralis dorsalis. The cholinesterase material suggested a division of the lateralis dorsalis into at least medial and lateral parts, but the connections of these regions were not analyzed in detail. The finding of clear chemoarchitectural subdivisions in the lateralis posterior-pulvinar complex and adjoining regions has practical significance as a guide to thalamic organization and raises the possibility that some extrageniculate and related transthalamic pathways may be differentiated from one another by the neurotransmitters they employ in the thalamus.

The thalamic projection to cortical area 17 in a congenitally anophthalmic mouse strain

The thalamocortical projection innervating area 17 in the congenitally anophthalmic ZRDCT-An mouse was compared with its counterpart in normal-eyed mice of different strains by the horseradish peroxidase method. The results indicate that, despite absence of retinal afferents and a reduction of its neuronal population to 76% of normal, the dorsal nucleus of the lateral geniculate body in the ZRDCT-An mouse projects to area 17 in an essentially normal topographic pattern. Our evidence also indicates the existence, both in normal-eyed and ZRDCT-An mice, of an extrageniculate thalamocortical projection to area 17, arising in particular from the nucleus lateralis posterior but in lesser degree also from the nucleus lateralis dorsalis. In both normal and anophthalmic mice, this extrageniculate projection favors the lateral and posterior parts of area 17; however, the projection to these parts is considerably greater in the congenitally anophthalmic than in the normal-eyed mouse. Compensatory innervation thus appears to occur in the anophthalmic mouse not only at the level of the primary retinorecipient nucleus of the geniculostriate system, but also at the level of the visual cortex that is once removed from the direct effects of congenital denervation.

Functional organization of some auditory nuclei in the guinea fowl demonstrated by the 2-deoxyglucose technique.

The auditory pathway of the Guinea Fowl was labeled with [C14]2-deoxy-D-glucose after stimulation with pure tones, harmonic tones and species-specific calls. In addition to other auditory nuclei, which showed more or less uniform labeling with the present technique, the n. mesencephalicus lateralis dorsalis (MLD) of the midbrain, as well as field L and parts of the hyperstriatum ventrale in the telencephalon, showed a stripe-pattern of labeling after stimulation with a pure tone. The position and orientation of the tone-activated striped areas in field L, observed after stimulation with different tones, correspond to isofrequency contours obtained with microelectrode recordings. The labeling of the three congruent tonotopically organized layers of field L (L1, L2, and L3) was not uniform along the anterior-posterior axis of the field. Harmonic tones produced multiple reactive stripes each of which corresponded to the stripe characteristic of a particular harmonic presented as a pure tone. The species-specific Iambus-call labeled the tonotopic area of field L that corresponds to the frequency band with the highest energy of the call. The hyperstriatum ventrale generally showed a weaker pattern of labeling that, however, resembled the labeling in field L.

Functional organization of the tectothalamic section of the transcollicular visual afferent channel

On the basis of the results of electrical stimulation of the optic tract and upper layers of the superior colliculus in cats anesthetized with pentobarbital maps were compiled of the distribution of evoked potentials of the posterior thalamic nuclear complex, including the pulvinar and n. lateralis posterior, posterior, suprageniculatus, and lateralis dorsalis. Functional projections of the superior colliculus and optic tract to the posterior thalamus were shown to differ from each other. In response to stimulation of the superior colliculus the distribution of projections was more regular than to stimulation of the tract. Fibers running from the optic tract occupy a smaller territory than fibers from the superior colliculus. It is suggested that the transcollicular afferent channel of the visual system is not reduced in the course of evolution but, on the contrary, it acquires connections with the younger thalamic formations of the brain and assume more complex functions.

Atlas of the distribution of monoamine-containing nerve cell bodies in the brain stem of the cat.

The distribution and morphological characteristics of monoamine (MA)-containing neuronal somata in the brain stem of kittens and of adult cats were studied by means of the Falck-Hillarp histofluorescence method. This investigation has shown, among other things, that in the midbrain of the cat the catecholamine (CA) perikarya are chiefly confined to the pars compacta of the substantia nigra, the ventromedial tegmental area, the nucleus linearis rostralis and the nucleus parabrachialis pigmentosus. Numerous CA neurons are also present in the dorsolateral part of the pontine tegmentum but also within the nucleus subcoeruleus, in nuclei lemnisci lateralis dorsalis and in nuclei parabrachialis lateralis and medialis. In the medulla, a few CA neuronal somata are lying near the hypoglossal nucleus whereas a larger number of CA cell bodies occur at the level of nucleus reticularis lateralis and in nucleus paragigantocellularis lateralis. On the other hand, most of the serotonin (5-HT) perikarya are confined to the raphe nuclei of the brain stem: nuclei raphe dorsalis, centralis superior, raphe pontis, raphe magnus, raphe pallidus and raphe obscurus. Some 5-HT neuronal somata are also found lateral to the pyramidal tract and to the inferior olivary complex. The various similarities and differences in respect to the pattern of the topographical distribution of MA neurons in the brain stem of the cat as compared to that of other mammals are discussed.

Histochemical fiber composition of lumbar back muscles in the cat.

A histochemical analysis has been performed of the activity of myofibrillar ATPase, NADH2tetrazolium-reductase, succinic dehydrogenase and phosphorylase and of the content of fat and glycogen in the muscles of the cat's lumbar back region. The correlation between the fiber composition and the previously studied contraction properties of the muscles was analyzed. All muscles contain fibers with a low activity (type I) and such with a high activity (type II) of myofibrillar ATPase following preincubation at pH 9.4. Type II fibers showed either a low (type II A) or an intermediate (type II B) reaction when stained for ATPase, preincubation at pH 4.6. Type I fibers have a high, II A an intermediate-high and II B fibers a low activity of oxidative enzymes. The longissimus, iliocostalis and sacrocaudalis dorsalis lateralis muscles are characterized by high percentages of type II B fibers and low proportions of type I and type II A fibers. The central region of the longissimus which is connected to a well developed intermuscular septum is composed of a high proportion of type I fibers. The multifidi, interspinales and intertransversarii mediales muscles have higher proportions of type I and type II A fibers than the other muscles in the region.

The thalamic afferents to the inferior parietal lobule of the rhesus monkey

AbstractThe inferior parietal lobule (IPL) of the monkey is the homologous region to the supramarginal and angular gyri in man, subserving language and related cortical functions. We have examined specific zones of the IPL by injecting eight monkeys with retrogradely transported HRP, and located the positive cells in the thalamic sections with the assistance of an X‐Y plotter and reference to the atlas of Olszewski ('52). Projections to the IPL were found in the following thalamic nuclei: Anterior (Anterior Medial, Anterior Ventral); Lateral (Ventral Anterior, Ventral Anterior magnocellularis, Ventral Lateral caudalis, Pulvinar oralis, medialis, lateralis and inferior, Lateral Posterior and Lateral Dorsal); Medial (Medialis Dorsalis densocellularis, parvocellularis, and multiformis); Midline and Intralaminar (Centralis densocellularis, Centralis lateralis, Centralis inferior, Centralis superior lateralis, Subfascicularis parvocellularis, Paracentralis and Parafascicularis); and Posterior (Limitans, Suprageniculatus and Geniculatus Medialis magnocellularis).A major projection to the superior portion of the IPL was from the anterior nuclei and Paracentralis of the intralaminar group. Ventralis Lateralis and oral Pulvinar projected primarily to the anterior‐inferior portion of the IPL, whereas Lateral Posterior projected most strongly to the anterior and superior portion. The major projection of the lateral Pulvinar was to the mid‐superior portion of the IPL and to area 19. The projections of the inferior Fulvinar were heaviest to area 19, but there was some overlap in the mid‐superior portion of the IPL with the medial and lateral Pulvinar. The major projection from the posterior thalamic nuclear complex was to the mid‐IPL.The heterogeneous input from the thalamus to the IPL was not anticipated on the basis of prior anterograde or retrograde degeneration studies, and suggests that classical subdivisions of specific and associational thalamic nuclei should be revised with the axonal transport methods of study.