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.     

Effects of excitation of the central nuclei of the cerebellum on the activity of neurons in the pyramidal tract

The effect of excitation of the contralateral nuclei of the cerebellum on the activity of anti-dromically-identified fast and slow pyramidal neurons in the sensorimotor region (SMR) of the cerebral cortex was investigated in delicate experiments on unnarcotized cats immobilized with procurane. It was found that excitation of the above nuclei could evoke peak responses in the neurons of the pyramidal tract (PT), but more often it modified their background activity. These responses were more pronounced on excitation of the intermediate nucleus (IN) or the dentate nucleus (DN), although they also often arose on excitation of the fastigial nucleus (FN). Qualitatively different effects (stimulative and inhibitory) were observed in some neurons on excitation of different nuclei in the cerebellum. It was found that the nature of the responses by fast neurons in the PT to excitation of the central nuclei in the cerebellum did not differe substantially from the nature of the responses by slow neurons, but that the responses of the latter arose with a longer latent period, and in most cases were less pronounced.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 3, No. 1, pp. 22–31, January–February, 1971.     

Afferent connections of the ventral magnocellular section of the cat red nucleus

The location within the brain of labeled neurons giving rise to projections to the ventral magnocellular section of the red nucleus were investigated by means of microiontophoretically injected horseradish peroxidase. Projections were identified from many cortical, thalamic, and hypothalamic structures and from the head of the caudate nucleus, septum, globus pallidus, anterior commissure nucleus, central amygdalar nucleus, field of Forel, Zona incerta, and a number of brainstem structures. Findings in accordance with those found in the literature were obtained on projections to the red nucleus from the coronary and cruciate cortical sulci, the midbrain and dentate (lateral) cerebellar nuclei, subststantia nigra, nucleus gracilis, and the cuneate nucleus. Trajectories of retrogradely labeled fiber systems of the red nucleus are described.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 20, No. 5, pp. 680–687, September–October, 1988.     

Activation of cat pontine nuclei neurons produced by cortico- and cerebellofugal impulses

Extracellular recording techniques were used on cats anesthetized with Nembutal to illustrate antidromic activation of pontine neurons produced by stimulating the medial and occasionally the superior cerebellar peduncle, the cerebellar central nuclei, pyramidal tract, and sensorimotor region of the cortex. Of the pontine nucleus projection, that extending to the lateral cerebellar nucleus was the most clearly defined. Stimulation of the pyramidal tract, central cerebellar nuclei and the superior cerebellar peduncle was found to produce monosynaptic excitation of pontine neurons. The significance and special features of the connections identified are discussed in connection with cortico-pontocerebellar system function.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Amenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 20, No. 1, pp. 38–48, January–February, 1988.     

Effects of stimulation of peripheral nerves,the lateral reticular nucleus,and the inferior olive on fastigial neurons of the cat cerebellum

Activity of fastigial neurons was investigated during stimulation of peripheral nerves of the fore- and hind limbs and also of brain-stem nuclei — the lateral reticular nucleus and inferior olive, transmitting indirect peripheral impulses to the cerebellum, in cats under superficial pentobarbital anesthesia. Stimulation of the nerves was accompanied by excitation of most neurons tested, reflected in repeated discharges to a single stimulus. Three main groups of responses latencies were distinguished: Those corresponding to conduction of peripheral impulses along slow and (partly) fast spinocerebellar tracts were predominant. Stimulation of the lateral reticular nucleus and inferior olive was accompanied by mono- and polysynaptic, and also by antidromic activation of fastigial neurons. Monosynaptic and antidromic activation of neurons are regarded as evidence of the presence of direct reticulo-and olivofastigial projections and of feedback in the system of these inputs into the nucleus fastigius respectively.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 13, No. 2, pp. 168–178, March–April, 1981.     

Antidromic and synaptic potentials evoked in neurons of the lateral vestibular nucleus by stimulation of the interstitial nucleus of Cajal and Darkshevich's nucleus in cats

Effects of stimulation of the interstitial nucleus of Cajal and Darkshevich's nucleus on unit activity in the lateral vestibular nucleus of Dieters were investigated in cats anesthetized with pentobarbital. Stimulation of the above-mentioned structures was shown to lead to antidromic and orthodromic activation of Dieters neurons. Axon collateral of vestibular neurons, ascending to the above-mentioned brain-stem structures were discovered electrophysiologically. Stimulation of the nuclei of Cajal and Darkshevich was shown to evoke mono- and polysynaptic EPSPs and IPSPs in neurons of Deiters nucleus. Convergence of influences from both nuclei on the neurons studied was demonstrated. The particular features and functional role of the influences observed are discussed.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 822–829, November–December, 1984.     

Afferent connections of the cat lateral vestibular nucleus

Location within the brain of HP-labeled neurons (origins of projections to the lateral vestibular nucleus) was investigated by iontophoretic injection of this enzyme. Bilateral projections to the following midbrain structures were revealed: the field of Forel, interstitial nuclei of Cajal, oculomotor nerve nuclei, and the red nucleus — to all parts of the lateral vestibular nucleus. Bilateral projections were also shown from more caudally located structures, viz. the superior, medial and inferior (descending) vestibular nuclei, Y groups of the vestibular nuclear complex, facial nucleus and hypoglossi, nucleus prepositus nervi hypoglossi and caudal nuclei of the trigeminal tract; ipsilateral projections from crus IIa of lobulus ansiformus of the cerebellar hemisphere; contralateral projections from the bulbar lateral reticular nucleus and Deiter's nucleus. A tonic organization pattern of afferent inputs from a number of brainstem formations to the dorsal and ventral lateral vestibular nucleus is revealed and trajectories of HP-labeled fiber systems projecting to Deiter's nucleus described.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 20, No. 4, pp. 494–503, July–August, 1988.     

Plastic synaptic reorganization in the sensorimotor cortex of adult cats after lesioning of the contralateral cerebellar nucleus interpositus

Intact cats and animals undergoing lesioning of the contralateral cerebellar nucleus interpositus between one and six months previously were used in this research, employing intracellular recording techniques and investigating the response of corticospinal neurons (CSN) to stimulating the aforementioned nucleus, the ipsilateral cerebellar nucleus interpositus, and the ventrolateral thalamic nucleus. A reduction was found in the stage of rise to peak in monosynaptic thalamocortical EPSP in CSN of operated animals, with a low axonal conduction velocity, pointing to distant terminal dendrosomatic sprouting and formation of new synapses at proximal sections of the CSN somatodendritic membrane. Findings are presented on formation of ipsilateral interpositothalamocortical projections duplicating similar contralateral projections in intact animals. Contralateral cortico-interposital collaterals were found in intact animals and similar sprouting of ipsilateral origin in those which had undergone surgery.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 22, No. 6, pp. 761–771, November–December, 1990.     

Neuronal mechanisms of interaction between the red nucleus and other brain stem structures

Axon collaterals of rubrospinal neurons running to many brain stem structures were identified in acute experiments on cats by a technique of intracellular recording of antidromic action potentials in conjunction with collision testing. A systemic principle of organization of rubrospinal influences and also a tendency toward synchronous arrival of rubrospinal impulses at various brain stem centers were demonstrated. Most of these centers are relay nuclei, sending direct afferent projections to regions of the cerebellum which, in turn, control activity of the red nucleus. Besides such a loop, effecting dynamic cerebellar control over motor function, transmission of somatosensory information from nuclei of the dorsal columns of the spinal cord directly to the red nucleus was demonstrated. Special features of mono- and polysynaptic EPSPs evoked by stimulation of nuclei of the dorsal columns indicate that such PSPs arise in different regions of the soma-dendritic membrane of red nucleus neurons. The mechanisms of integration of descending motor volleys by the red nucleus are discussed.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 16, No. 5, pp. 665–678, September–October, 1984.     

Synaptic processes produced in cat rubrospinal neurons by stimulating the cerebellar nucleus interprositus

The activity produced in red nucleus rubrospinal neurons by stimulating the cerebellar nucleus interpositus was investigated in cats anesthetized with nembutal. Analysis of field potentials together with summated and single EPSP following paired and frequency stimulation of this structure revealed facilitation at cerebello-rubral synapses. It was found that this facilitation was not mediated by changes in presynaptic volleys. It is suggested that modification of the effectiveness of transmission is determined by characteristic features of the operation of cerebellar synapses on red nucleus neurons.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 19, No. 5, pp. 630–636, September–October, 1987.     

Synaptic processes evoked in red nucleus neurons by stimulation of the substantia nigra in cats

Synaptic processes in red nucleus neurons evoked by stimulation of different parts of the substantia nigra and nucleus interpositus of the cerebellum were investigated by an intracellular recording method in acute experiments on cats. Stimulation of this sort was shown to induce mono- and polysynaptic activation of rubrospinal neurons. Monosynaptic cerebellar and nigral excitatory influences were found to be very similar. These influences were shown to converge on the same rubrospinal neurons. The functional significance of inputs from the substantia nigra to the red nucleus for movement performance is discussed.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 13, No. 2, pp. 149–158, March–April, 1981.     

The neuronal organization of the dentate nucleus of the cerebellum

The intracellular activity of the neurons of the dentate nucleus was studied in cats anesthetized with Nembutal by means of their antidromic and synaptic excitation through stimulation of the red nucleus (RN) and the ventrolateral nucleus of the thalamus (VL), as well as the sensomotor cerebral cortex (CC) and the peripheral nerves of the posterior and anterior extremities. Several functionally delimited groups of neurons were isolated and studied. Efferent neurons, antidromically activated from nuclei of the brain stem, which did not react to stimulation of the peripheral nerves were placed in group I. Group II neurons were synaptically activated from the nuclei of the brain stem, and in a majority of cases also reacted to stimulation of the peripheral nerves and CC. Cells with a rhythmic background activity, which did not react to any of the types of stimulation used, comprised group III. Group IV was made up of neurons having the properties of intermediate neurons with a selective reaction to stimulation of a specific peripheral nerve or which experience broad convergence of the effects of different afferent impulsations.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 3, No. 2, pp. 154–165, March–April, 1971.     

Thalamic inputs to the motor cortex studied in cats by retrograde axonal horseradish peroxidase transport

Thalamic afferent inputs of the motor cortex (area 4) were studied in cats by retrograde axonal transport of horseradish peroxidase (HRP). The main concentration of HRP-labeled neurons was found in rostral zones of the relay nuclei (of the ventrolateral and ventrobasal complex). A few labeled neurons were found in the mediodorsal association nucleus, where their distribution is quite local. HRP-labeled neurons of nonspecific intralaminar nuclei, projecting into the motor cortex, are present only in single numbers and show no tendency toward grouping in any parts of these nuclei. The results are evidence that the motor cortex receives heterogeneous afferentation from various thalamic nuclei, and it is evidently this which guarantees the reliability of transmission of incoming information.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 17, No. 2, pp. 250–255, March–April, 1985.     

Spatial organization of inhibitory control of activity of vestibulospinal Deiters' neurons by Purkinje cells in the anterior lobe of the cerebellum

The topographical distribution of vestibulospinal neurons in Deiters' nucleus was investigated by a microelectrode method. By contrast with observations made in morphological experiments, the localization of antidromically identified vestibulocervical (C-neurons) and vestibulolumbar (L-neurons) cells was found not to be limited to the ventral middle and rostral third of the nucleus (the forelimb region) and caudodorsal part of the nucleus (hind limb region), but to include the whole of the ventral and dorsal half of the nucleus, respectively. The zones of localization of these two groups of neurons are not confined to a single layer: C-neurons are found in the dorsal half of the nucleus and L-neurons in its ventrocaudal part also. Analysis of the distribution of monosynaptic IPSPs arising in response to activation of Purkinje cells in the vestibulospinal neurons showed that C-neurons are controlled chiefly from the forelimb zone of the cerebellar cortex whereas L-neurons are controlled equally by inhibitory influences from the forelimb and hind limb zones of the anterior lobe of the cerebellar cortex.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 11, No. 1, pp. 54–64, January–February, 1979.     

Effect of the vermian cortex of the anterior lobe of the cerebellum on the background electrical activity of fastigial neurons

The effect of electrical stimulation of the vermian cortex of the anterior lobe of the cerebellum on the activity of neurons of different portions of the fastigial nucleus was studied in acute experiments on cats under light nembutal anesthesia. Inhibitory influences of the cortex (80.6% of the reacting neurons) were manifested in total blocking or decrease in the frequency of the background activity of the neurons and were characterized by a long aftereffect and "rebound." Stimulation of the cortex also had a blocking effect on the inhibitory interaction of adjacent nuclear elements. Facilitatory influences (14.5% of the neurons) were expressed either by an increase of spontaneous discharges of the neurons or by the appearance of activity in rhythm with the stimulation. The effectiveness of cortical stimulation depended on the localization of the stimulating electrodes. Zones of maximum density of projections to a given neuron of the nucleus and convergence and divergence of influences were found in the cerebellar cortex.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziolgiya, Vol. 2, No. 3, pp. 260–268, May–June, 1970.     

Neuronal analysis of projections from trigeminal nucleus caudalis to the facial nucleus in cats

Properties of neurons of the trigeminal nucleus caudalis, with projections into the facial nucleus, were investigated in cats by a microelectrode technique. These neurons were found to be located mainly in the ventral parts of the trigeminal nucleus caudalis and in the adjacent lateral reticular formation. Monosynaptic and polysynaptic activation of efferent neurons of the trigeminal nucleus caudalis was found in response to pyramidal impulsation. Repeated discharges were recorded in the test neurons in response to stimulation of their axons, to direct stimulation of the trigeminal nucleus caudalis, and also to stimulation of the pyramidal tract and facial nerve. The synaptic mechanisms of regulation of motoneuron activity in the facial nerve nucleus are discussed.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 13, No. 3, pp. 264–269, May–June, 1981.     

Rearrangement of parameters of efferent activity in generators of cyclic motor response produced by electrical stimulation of cerebellar inputs in cats

Rearrangement of the parameters of scratch and locomotor generators produced by electrical stimulation of the inferior olive and nucleus reticularis lateralis as well as the cerebellar fastigial nucleus and nucleus interpositus was investigated in decerebrate immobilized cats. Results showed that a comparable rearrangement of the time course of activity in both locomotor and scratch generators was produced by altering the nature of signals proceeding along mossy and climbing fibers alike. Maximum rearrangement of scratch and locomotor generator activity, as induced by electrical activation of the inferior olive and lateral reticular nucleus, is observed during the first half of flexor half-center operation in these generators. The scratch (unlike the locomotor) generator typically shows considerably rearranged efferent activity following electrical activation of nuclei of the cerebellum and cerebellar afferents. The article discusses mechanisms of cerebellar origin which may be responsible for exerting a corrective action on scratch and locomotor generators during change in the phase and amplitude parameters of cerebellar input signals.A. A. Bogomolets Institute of Physiology, Ukrainian Academy of Sciences, Kiev. Translated from Neirofiziologiya, Vol. 24, No. 2, pp. 131–140, March–April, 1992.     

Sources of thalamo-cortical afferents of the forelimb representation area in the first somatosensory zone of the cat cerebral cortex

Retrogradely labeled thalamic neurons—the sources of afferents in the focus of peak activity induced by radial nerve stimulation—were investigated in adult cats by means of microiontophoretic horseradish peroxidase injection into the first somatosensory zone of the cerebral cortex. Labeled cells were found mainly in the ventroposterolateral and a smaller proportion in the posteroventral medial thalamic nuclei. Labeled neurons were distributed in groups differing in their morphological parameters within these nuclei.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 20, No. 2, pp. 154–160, March–April, 1988.     

Effects of coagulation of thelocus coeruleus and pontine raphe nuclei on the background activity recorded from the rat cerebellar fastigial nucleus neurons

Simultaneous or separate coagulation of thelocus coeruleus (LC) and the pontine raphe nucleus (PRN) results in a significant increase of irregular-type background activity in the cerebellar fastigial nucleus neurons. There are also considerable changes in the dynamics of impulse sequences, in particular, the number of neurons with random interpulse intervals markedly increases. Destruction of theLC and/or PRN is followed by a marked drop in the mean frequency of discharges in the neurons of the fastigial nucleus.Neirofiziologiya/Neurophysiology, Vol. 26, No. 6, pp. 437–442, November–December, 1994.     

Development of human cerebellar nuclei. Morphometric study

The morphometric development of the human cerebellar nuclei was examined in 9 fetuses (16-40 weeks of gestation; WG), an infant (2 months old) and 2 adults (16 and 63 years old). With the morphological observation of serial sections of the brain containing the cerebellar nuclei, the authors measured sections to get several morphometric parameters: the volume of nuclear column and number, packing density and cell body area of neurons. Each nucleus (dentate, emboliform, globose and fastigial nucleus) was recognized even at 16 WG. Nerve cells containing Nissl bodies were observed in all nuclei after 23 WG. Degenerative changes were detected in some neurons for every nucleus at 21 and 23 WG. Three stages were observed in the developmental course of nuclear volume and neuronal packing density: the primary or undifferentiated stage at 16 WG, the secondary stage with variability at 21-32 WG and the tertiary stage with monotonous increase (nuclear volume) or gradual decrease (neuronal packing density) after 35 WG. No significant correlation between neuronal number and gestational age was noticed for every nucleus. The analysis of cell body area (neuronal size) demonstrated that the dentate neurons developed after the intermediate or fastigial neurons. It is concluded that there is a critical period between slightly before 20 WG and slightly after 30 WG, matched with the secondary stage in the development of the cerebellar nuclei.