Ascending and descending projections to the inferior colliculus in the rat

The ascending and descending projections to the central nucleus of the inferior colliculus (IC) were studied with the aid of retrograde transport of horseradish peroxidase (HRP). HRP-labelled cells were found in contralateral cochlear nuclei, where the majority of different cell types was stained. Few labelled cells were observed in the ipsilateral cochlear nuclei. HRP-positive neurones were found in all nuclei of the superior olivary complex on the ipsilateral side with the exception of the medial nucleus of the trapezoid body, which was never labelled either ipsilaterally or contralaterally. The largest concentration of HRP-labelled cells was usually observed in the ipsilateral superior olivary nucleus. Smaller numbers of labelled cells were present in contralateral nuclei of the superior olivary complex. Massive projections to the inferior colliculus were found from the contralateral and ipsilateral dorsal nucleus of the lateral lemniscus and ipsilateral ventral nucleus of the lateral lemniscus. Many neurones of the central and external nuclei of the contralateral inferior colliculus were labelled with HRP. Topographic organisation of the pathways ascending to the colliculus was expressed in the cochlear nuclei, lateral superior olivary nucleus and in the dorsal nucleus of the lateral lemniscus. HRP--positive cells were found in layer V of the ipsilateral auditory cortex, however, the evidence for topographic organisation was lacking.     

Electrophysiological investigation of cortico-hypothalamic relations in cats

Projections of different parts of the orbito-frontal cortex, the basal temporal cortex, and the hippocampus on hypothalamic nuclei were studied by recording focal responses in acute experiments on cats anesthetized with pentobarbital and chloralose. The proreal gyrus was shown to have local projections in the latero-dorsal zones of the preoptic region, in the rostral parts of the medial forebrain bundle, and also in the region of the lateral and posterior hypothalamus with the mammillary bodies. The orbital gyrus projects mainly to the latero-dorsal portions of the forebrain bundle, the latero-ventral part of the preoptic region, and the region of the lateral and latero-dorsal hypothalamic nuclei; projections from the orbital gyrus are relatively diffuse in character. The basal temporal cortex has diffuse projections in the central part of the preoptic region, in the latero-ventral parts of the medial forebrain bundle, and in the lateral mammillary body. No marked foci of activity were found in the hypothalamic structures during hippocampal stimulation. Diffuse projections of the hippocampus were traced in the ventral part of the preoptic region and the ventral regions of the medial forebrain bundle, and also in the lateral hypothalamus and in the lateral mammillary nucleus.A. M. Gor'kii Donetsk Medical Institute. Translated from Neirofiziologiya, Vol. 8, No. 4, pp. 358–365, July–August, 1976.     

Projections of the central cerebellar nuclei to the intralaminar thalamic nuclei in cats

Projections of the central cerebellar nuclei to the intralaminar thalamic nuclei were studied in cats with the use of light and electron microscopy. Almost all intralaminar nuclei were shown to obtain cerebello-thalamic projections. The entire complex of the central cerebellar nuclei serves as a source of such projections; yet, involvement of different nuclei is dissimilar. Destruction of the central and, especially, caudal regions of the fastigial nucleus evoked in the intralaminar thalamic nuclei degenerative changes in the nerve fibers (from swelling and development of varicosities up to total fragmentation). Pathological phenomena could be noticed in the most caudal regions of the above thalamic nuclear group, including the medial dorsal nucleus. Projections of the cerebellar interpositus nucleus were directed toward nearly the same regions of the intralaminar nuclei; degeneration was more intensive (covered thecentrum medianum) when posterior regions of the interpositus nucleus were destroyed. Destruction of the lateral cerebellar nucleus evoked a similar pattern of pathological changes, but degeneration was also observed in some structures of the ventral and anterior nuclear groups of the thalamus. Electron microscopic examination showed that degeneration of dark and light types developed in the fiber preterminals and terminals. It can be concluded that the central cerebellar nuclei project not only to the ventral complex of the thalamic nuclei, but also to the anterior, medial, and intralaminar nuclear groups (rostral and caudal portions).     

Dorsal thalamic connections of the ventral lateral geniculate nucleus of rats

In order to understand better the organisation of the ventral lateral geniculate nucleus of the ventral thalamus, this paper has examined the patterns of connections that this nucleus has with various nuclei of the dorsal thalamus in rats. Injections of biotinylated dextran or cholera toxin subunit B were made into the parafascicular, central lateral, posterior thalamic, medial dorsal, lateral dorsal, lateral posterior, dorsal lateral geniculate, anterior, ventral lateral, ventrobasal and medial geniculate nuclei of Sprague-Dawley rats and their brains were processed using standard tracer detection methods. Three general patterns of ventral lateral geniculate connectivity were seen. First, the parafascicular, central lateral, medial dorsal, posterior thalamic and lateral dorsal nuclei had heavy connections with the parvocellular (internal) lamina of the ventral lateral geniculate nucleus. This geniculate lamina has been shown previously to receive heavy inputs from many functionally diverse brainstem nuclei. Second, the visually related dorsal lateral geniculate and lateral posterior nuclei had heavy connections with the magnocellular (external) lamina of the ventral lateral geniculate nucleus. This geniculate lamina has been shown by previous studies to receive heavy inputs from the visual cortex and the retina. Finally, the anterior, ventral lateral, ventrobasal and medial geniculate nuclei had very sparse, if any, connections with the ventral lateral geniculate nucleus. Overall, our results strengthen the notion that one can package the ventral lateral geniculate nucleus into distinct visual (magnocellular) and non-visual (parvocellular) components.     

Intrathalamic afferent connections of the median center of the thalamus

Microiontophoretic local injection of horseradish peroxidase (HP) have been performed into the median center (MC). Many thalamic nuclei are sources of projections into MC, though the role of each nucleus is not equivalent. MC is predominantly connected with nonspecific formations (reticular, parafascicular, central-lateral, paracentral, ventromedial, paraventricular). Among them the reticular nucleus is distinguished, it sends its efferent fibers from the ventral, ventrolateral and lateral areas. In the anterior part of the reticular nucleus there are no HP-labelled cells. In MC little projections from specific nuclei (ventrobasal complex, ventrolateral nucleus, geniculate body) are presented, as well as simple projections from the associative nuclei. The data obtained are in keeping with electron physiological investigations.     

Relationship between thalamic projections and different areas of the parietal association cortex in cats

Thalamic neuronal projections to the parietal association cortex were investigated in cats applying techniques of retrograde axonal transport of two fluorescent dyes (primuline and fast blue). The dorsal thalamic pulvinar (PL) as well as the dorsal and caudal lateral posterior nucleus (LP) were found to project mainly to the central suprasylvian gyrus (CSSG), while the ventral PL and the ventrorostral LP send out projections to rostral sites of the same gyrus (RSSG). Neurons with dual labeling were found in the PL, LP, suprageniculate, anteroventral, and ventrolateral thalamic nuclei following a single injection of two different markers into the RSSG and CSSG, as well as the centrolateral, paracentral, and centromedial nuclei. Topical organization of sources of cortical projections within the PL-LP complex can apparently provide a high level of discrimination of visual signals by individual cortical units. At the same time, the RSSG and CSSG appear to function in harmony to a considerable extent during integration of information of differing cortical origin; this could point to a lack of differentiation on the part of the RSSG and CSSG, corresponding to feline cortical areas 5 and 7 approximately.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 2, pp. 135–142, March–April, 1991.     

Striatal projections from the lateral and posterior thalamic complexes. An anterograde tracer study in the cat

Striatal projections from the lateral intermediate (LI) and posterior (Po) thalamic complexes were studied with the anterograde tracers wheat germ agglutinin-horseradish peroxidase and Phaseolus vulgaris leucoagglutinin. Projections to the lateral part of the head and body of the caudate nucleus (CN) and to the putamen (Pu) were found to arise from the ventral parts of the caudal subdivision of the LI besides the well established sources in the intralaminar and ventral thalamic nuclei. No projections to the CN and only a few to the Pu were found to arise from the medial division of the Po. The presence of terminal and intercalated varicosities in the thalamostriatal fibers suggests that they form both terminal and en passant synapses. Thalamostriatal fibers from these thalamic sectors were unevenly distributed within the CN, with patches of either low-density innervation or with no projections at all interspersed within irregular, more densely innervated areas. The former coincided with the acetylcholinesterase-poor striosomes and the latter areas of dense projection with the extrastriosomal matrix.     

The neurons of origin of non-cortical afferent connections to the oculomotor nucleus. A retrograde labeling study in the rabbit.

The cellular origin of the brainstem projections to the oculomotor nucleus in the rabbit has been investigated by using free (HRP) and lectin-conjugated horseradish peroxidase (WGA-HRP). Following injections of these tracers into the somatic oculomotor nucleus (OMC), retrogradely labeled cells have been observed in numerous brainstem structures. In particular, bilateral labeling has been found in the four main subdivisions of the vestibular complex, predominantly in the superior and medial vestibular nuclei and the interstitial nucleus of Cajal, while ipsilateral labeling was found in the rostral interstitial nucleus of the medial longitudinal fascicle (Ri-MLF), the Darkschewitsch and the praepositus nuclei. Neurons labeled only contralaterally have been identified in the following structures: mesencephalic reticular formation dorsolateral to the red nucleus, abducens internuclear neurons, group Y, several areas of the lateral and medial regions of the pontine and medullary reticular formation, ventral region of the lateral cerebellar nucleus and caudal anterior interpositus nucleus. This study provides also information regarding differential projections of some centers to rostral and caudal portions of the OMC. Thus, the rostral one-third appears to receive predominant afferents from the superior and medial vestibular nuclei, while the caudal two-thirds receive afferents from all the four vestibular nuclei. Finally, the group Y sends afferents to the middle and caudal, but not to the rostral OMC.     

Distribution of trigeminothalamic and spinothalamic lamina I terminations in the cat

The distribution in the thalamus of terminal projections from lamina I neurons of the trigeminal, cervical, and lumbosacral dorsal horn was investigated with the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) in the cat. Iontophoretic injections were guided by single- and multi-unit physiological recordings. The injections in particular cases were essentially restricted to lamina I, whereas in others they spread across laminae I-III or laminae I-V. The trigemino- and spinothalamic (TSTT) terminations were identified immunohistochemically. In all cases, regardless of the level of the injections, terminal fibers were consistently distributed in three main locations: the submedial nucleus; the ventral aspect of the basal ventral medial nucleus and ventral posterior nuclei; and, the dorsomedial aspect of the ventral posterior medial nucleus. The terminal fields in the submedial nucleus and the ventral aspect of the ventral posterior group were topographically organized. Terminations along the ventral aspect of the ventral posterior group extended posterolaterally into the caudal part of the posterior nucleus and anteromedially into the ventromedial part of the ventral lateral nucleus. In several cases with trigeminal lamina I injections, a terminal labeling patch was observed within the core of the ventral posterior medial nucleus. In cases with spinal lamina I injections, terminations were also consistently found in the lateral habenula, the parafascicular nucleus, and the nucleus reuniens. Isolated terminal fibers were occasionally seen in the zona incerta, the dorsomedial hypothalamus, and other locations. These anatomical observations extend prior studies of TSTT projections and identify lamina I projection targets that are important for nociceptive, thermoreceptive, and homeostatic processing in the cat. The findings are consistent with evidence from physiological (single-unit and antidromic mapping) and behavioral studies. The novel identification of spinal lamina I input to the lateral habenula could be significant for homeostatic behaviors.     

Distribution of trigeminothalamic and spinothalamic lamina I terminations in the cat

The distribution in the thalamus of terminal projections from lamina I neurons of the trigeminal, cervical, and lumbosacral dorsal horn was investigated with the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) in the cat. Iontophoretic injections were guided by single- and multi-unit physiological recordings. The injections in particular cases were essentially restricted to lamina I, whereas in others they spread across laminae I–III or laminae I–V. The trigemino- and spinothalamic (TSTT) terminations were identified immunohistochemically. In all cases, regardless of the level of the injections, terminal fibers were consistently distributed in three main locations: the submedial nucleus; the ventral aspect of the basal ventral medial nucleus and ventral posterior nuclei; and, the dorsomedial aspect of the ventral posterior medial nucleus. The terminal fields in the submedial nucleus and the ventral aspect of the ventral posterior group were topographically organized. Terminations along the ventral aspect of the ventral posterior group extended posterolaterally into the caudal part of the posterior nucleus and anteromedially into the ventromedial part of the ventral lateral nucleus. In several cases with trigeminal lamina I injections, a terminal labeling patch was observed within the core of the ventral posterior medial nucleus. In cases with spinal lamina I injections, terminations were also consistently found in the lateral habenula, the parafascicular nucleus, and the nucleus reuniens. Isolated terminal fibers were occasionally seen in the zona incerta, the dorsomedial hypothalamus, and other locations. These anatomical observations extend prior studies of TSTT projections and identify lamina I projection targets that are important for nociceptive, thermoreceptive, and homeostatic processing in the cat. The findings are consistent with evidence from physiological (single-unit and antidromic mapping) and behavioral studies. The novel identification of spinal lamina I input to the lateral habenula could be significant for homeostatic behaviors.     

Central connections of the olfactory bulb in the goldfish,Carassius auratus

Summary The central connections of the goldfish olfactory bulb were studied with the use of horseradish peroxidase methods. The olfactory bulb projects bilaterally to ventral and dorsolateral areas of the telencephalon; further targets include the nucleus praeopticus periventricularis and a caudal olfactory nucleus near the nucleus posterior tuberis in the diencephalon, bilaterally. The contralateral bulb and the anterior commissure also receive an input from the olfactory bulb. Contralateral projections cross in rostral and caudal portions of the anterior commissure and in the habenular commissure. Retrogradely labeled neurons are found in the contralateral bulb and in three nuclei in the telencephalon bilaterally; the neurons projecting to the olfactory bulb are far more numerous on the ipsilateral side than in the contralateral hemisphere. Afferents to the olfactory bulb are found to run almost entirely through the lateral part of the medial olfactory tract, while the bulb efferents are mediated by the medial part of the medial olfactory tract and the lateral olfactory tract. Selective tracing of olfactory sub-tracts reveals different pathways and targets of the three major tract components. Reciprocal connections between olfactory bulb and posterior terminal field suggest a laminated structure in the dorsolateral telencephalon.     

Thalamic relay of somatic and visceral signals to the orbital cortex

We investigated the role of different thalamic nuclei in the relaying of afferent signals into the anterior section of the coronary gyrus and into the orbital gyrus, using the evoked-potentials method, in delicate experiments on cats under Nembutal or Nembutal-chloralose narcosis, and also in experiments on cats not anesthetized but immobilized by injection of succinyl choline. Specific projection zones of the lingual, vagus, and glosso-pharyngeal nerves have been charted in the anterior coronary gyrus. The thalamic relay for that region is the medial pole of the ventral posterior nucleus. The orbital gyrus contains associative projections of both somatic and visceral nature. The relay for signal transmission in this region is also located in the ventral posterior nucleus. Relaying takes place, however, not in the central parts of the nucleus, where projections of the corresponding receptor zones have been charted, but nearer its lower medial surface. There is also an indirect route for associative projections, passing through the medial center and the intralaminar nuclei. That route emerges into the cortex through the ventral anterior and reticular nuclei. A feature of the projections of the vagus nerve in the orbital cortex is the existence of a supplementary region that exhibits responses, lying along the sulcus rhinalis. It was found that relaying for that region takes place in the ventral medial and submedial nuclei of the thalamus.N. I. Pirogov Vinnitsa Medical Institute. Translated from Neirofiziologiya, Vol. 1, No. 1, pp. 65–72, July–August, 1969.     

Unit responses of the medial group of thalamic nuclei to stimulation of the frontobasal regions of the neocortex

In acute experiments on cats anesthetized with pentobarbital and chloralose, single-unit and focal responses of the medial group of thalamic nuclei (mediodorsal, central lateral, paracentral, central medianum, parafascicular) were studied to stimulation of the frontobasal regions of the cortex (proreal, posterior orbital, basal temporal regions). Depending on the number of neurons responding to cortical stimulation and on the length of the latent period of the responses three functionally heterogeneous subdividions of the medial nuclei were distinguished; the parvocellular and magnocellular portions of the mediodorsal nucleus and the intralaminar nuclei with the parafascicular complex. On the basis of responses of neurons activated antidromically by stimulation of the same cortical region and synaptically by stimulation of another region, the concept of the integrative function of nuclei of the medial group, integrating the frontobasal zones of the neocortex with the aid of neuron circuits in which the medial nuclei are included, is argued.M. Gor'kii Donetsk Medical Institute. Translated from Neirofiziologiya, Vol. 9, No. 1, pp. 11–18, January–February, 1977.     

A horseradish peroxidase study on the mammillothalamic tract in the rat

The mammillary projections to the anterior thalamic nuclei were investigated in the rat, using the horseradish peroxidase (HRP) method. Pars centralis of the medial mammillary nucleus projects to the medial portion of the ateromedial nucleus (AM). Pars medialis (Mm) of the medial mammillary nucleus sends fibers to the ipsilateral AM and sparsely to the medial portion of the contralateral side. The ventral and dorsal portions of Mm project to the anterior and posterior portions of AM, respectively. The pars latralis (Ml) and pars posterior (Mp) of the medial mammillary nucleus send fibers predominantly to the ipsilateral anteroventral nucleus and sparsely to the contralateral side. A slight difference between Ml and Mp projections was observed. The lateral mammillary nucleus projects bilaterally to the anterodorsal nucleus.     

Afferent connections of the basolateral division of the amygdaloid complex of the cat brain

Injection of horseradish peroxidase into the basal macrocellular and lateral nuclei of the amygdaloid complex (BLAC) in the cat brain has revealed their rich thalamic afferentation. On the BLAC there are massive projections of: a) nuclei of the middle line of the precommissural pole of the dorsal thalamus (anterior parts of the paratenial, interanteromedial and reunial nuclei), as well as the whole anterior paraventricular nucleus, medial part of the ventral posteromedial nucleus; b) postcommissural nuclei of the dorsal thalamus; some "nonacustical" nuclei of the internal geniculate body (ventrolateral nucleus, medial and macrocellular parts and the most caudal end of the internal geniculate body). Rather essential are projections of the "posterior group nuclei", those of the suprageniculate nucleus, of some parts of the ventral thalamus (subparafascicular nucleus, marginal and peripeduncular nuclei) and parabrachial nucleus. Scattered single projections are obtained from all hypothalamic parts (most of all the ventromedial nucleus), reticular nuclei of the septum, substantia innominata, substantia nigra, truncal nuclei of the raphe. Variety of the dorsal thalamic nuclei, sending their fibers to the BLAC reflects variety of sensory information, that gets here, according to its modality, degree of its differentiation and integrity. A number of the dorsal thalamus nuclei, owing to abundance of labelled neurons, can be considered as special relay thalamic nuclei for the BLAC resembling corresponding relay nuclei for the new cortex.     

Relation between the septal nuclei and the amygdaloid complex of the brain of the cat

By means of retrograde and anterograde transport of horseradish peroxidase method it has been demonstrated in two series of experiments with injecting the enzyme into separate septal nuclei and the amygdaloid complex in cats that most of amygdaloid nuclei (cortico-medial, central and baso-lateral) are reciprocally connected only with two nuclei in the septum: with the nucleus of the diagonal bundle of Broca and with the nucleus of the terminal strip bed. The projections studied are topically organized. The cortico-medial and basal nuclei of the amygdaloid complex are reciprocally connected with the ventral part of the diagonal bundle of Broca and with the terminal strip bed nucleus. The central nucleus of the amygdala has reciprocal projections only with the terminal strip bed nucleus, and with the ventral part of the diagonal bundle of Broca it has only a unilateral connection. On the contrary, the lateral nucleus of the amygdala is reciprocally connected with the ventral part of the diagonal bundle of Broca, and is only projected on the terminal strip bed nucleus without getting any projections from it.     

Efferent connections of the striatum in Tupinambis nigropunctatus

The striatum of the lizard Tupinambis nigropunctatus lies in the lateral wall of the telencephalon and consists of two major subdivisions: the dorsal striatum and the ventral striatum. Electrolytic lesions were placed in all parts of the striatal complex and in adjacent areas and the subsequent anterograde degeneration was studied using the Nauta-Gygax and Fink-Heimer techniques. Lesions in the dorsal striatum cause terminal degeneration in the ventral striatum both ipsi- and contralaterally. In addition, projections have been found to the lateral amygdaloid nucleus and to parts of the dorsal striatum not affected by the lesion. Following lesions in the ventral striatum fiber degeneration could always be observed in the ventral peduncle of the lateral forebrain bundle. Corresponding terminal degeneration was found in the anterior and posterior entopeduncular nuclei, the tegmentum mesencephali, the substantia nigra, the prerubral area, the mesencephalic central grey and the lateral cerebellar nucleus. When the large celled part of the ventral striatum was involved in the lesion additional degeneration could be traced to the nucleus rotundus via the dorsal peduncle of the lateral forebrain bundle.     

Afferent connections of the dorsal magnocellularis area of the cat red nucleus

Location within the brain of retrogradely labeled neurons putting out projections from the dorsal magnocellularis area of the red nucleus was investigated by means of microiontophoretic injection of horseradish peroxidase into the dorsal magnocellularis area of the cat red nucleus. Projections were found from a number of hypothalamic nuclei, the centrum medianum, parafascicular and subthalamic nuclei, zone incerta, Forel's field, nucleus medialis habenulae, pontine and bulbar reticular formation, and the following midbrain structures: the central gray matter, superior colliculus, Cajal's interstitial nucleus, reticular formation, and the contralateral red nucleus. Projections were also identified proceeding from more caudally located structures: the cerebellar fastigial nucleus, facial nucleus, medial vestibular and dorsal lateral vestibular nuclei, and ventral horns of the spinal cord cervical segments. Connections between the substantia nigra and the red nucleus were clarified. Projections to the red nucleus from the cerebral cortex, interstitial and dentate (lateral) cerebellar nuclei, the nucleus gracilis and cuneate nucleus were found, confirming data presented in the literature. Bilateral trajectories of retrogradely labeled fiber systems are described.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 19, No. 6, pp. 810–816, November–December, 1987.     

Cytoarchitectonic study of the brain of a perciform species, the sea bass (Dicentrarchus labrax). I. The telencephalon

A cytoarchitectonic analysis of the telencephalon of the sea bass Dicentrarchus labrax, based on cresyl violet-stained serial transverse sections, is presented. Rostrally, the brain of the sea bass is occupied by sessile olfactory bulbs coupled to telencephalic hemispheres. The olfactory bulbs comprise an olfactory nerve fiber layer, a glomerular layer, an external cellular layer, a secondary olfactory fiber layer, and an internal cellular layer. Large terminal nerve ganglion cells are evident in the caudomedial olfactory bulbs. We recognized 22 distinct telencephalic nuclei which were classified in two main areas, the ventral telencephalon and the dorsal telencephalon. The ventral telencephalon displays four periventricular cell masses: the dorsal, ventral, supracommissural, and postcommissural nuclei; and four migrated populations: the lateral, central, intermediate, and entopeduncular nuclei. In addition, a periventricular cell population resembling the lateral septal organ reported in birds is observed in the ventral telencephalon of the sea bass. The dorsal telencephalon contains 13 nuclei, which can be organized into five major zones: the medial part, dorsal part, lateral part and its ventral, dorsal, and posterior divisions, the central part, and posterior part. Based on histological criteria, two cell masses are recognized in the ventral division of the lateral part of the dorsal telencephalon. The nucleus taenia is found in the caudal area of the dorsal telencephalon, close to the ventral area. This study represents a useful tool for the precise localization of the neuroendocrine territories and for the tracing of the neuronal systems participating in the regulation of reproduction and metabolism in this species.     

Afferent connections of the adjoining nucleus with the amygdaloid body and dopaminergic mesencephalic structures of the cat brain

By means of the retrograde axonal transport of horseradish peroxidase and luminescent markers the data have been obtained on topical organization of projections of the basal nucleus of the amygdaloid body, of the ventral field of the operculum and of the substantia nigra nuclei to the adjoining nucleus. In the medial and lateral segments of the adjoining nucleus the terminal fields of these structures overlap and have collaterals in the nuclei of the striopallidum. The interaction of limbic and motor informations in the adjoining nucleus is discussed.