Hypothalamic influences on unit activity in the cat sensomotor cortex

Experiments on unanesthetized, immobilized cats showed different effects of individual hypothalamic nuclei on spontaneous unit activity in the sensomotor cortex. Compared with the posterior hypothalamic nucleus (PHN) and its anteromedial region (AMH), in response to stimulation of the lateral hypothalamic nucleus (LHN) changes in spontaneous activity were more frequently found. The ratio between activation and inhibitory responses was 36 and 36% for AMH, 51 and 30% for LHN, and 47 and 28% for PHN. An approximately equal number of sensomotor neurons (27–34%) gave tonic responses. Phasic changes in spontaneous activity were observed more often in response to stimulation of LHN, less frequently to stimulation of AMH and PHN. Responses of "nonpyramidal" neurons to stimulation of AMH and LHN were identical. "Pyramidal" units were more sensitive to LHN stimulation. Variations in hypothalamic effects depending on the type of response of sensomotor neurons to sensory stimuli were detected. Cells with tonic responses were more susceptible to influences of LHN and AMH than cells which responded by phasic changes in spontaneous activity to sensory stimuli. Fewer still positive responses were recorded in areactive neurons.Medical Institute, Chita. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 115–122, March–April, 1972.     

Relations between the superior colliculus and sensomotor cortex in conscious rabbits

The tonic influence of the superior colliculus (SC) on the formation of visual evoked responses of the sensomotor cortex (SMC) was demonstrated in experiments on conscious rabbits. The influence of SC on the function of SMC was found to be realized with the involvement of tectothalamocortical (through the nucleus lateral is posterior thalami — NLPT) connections. SMC of the conscious rabbit, in turn, exerts a phasic inhibitory influence on visual function of SC. The findings are discussed in the light of involvement of tectocortical and corticotectal inter-relations in the organization of visuomotor integration, which is essential for visually controlled behavior.A. I. Karaev Institute of Physiology, Azerbaidzhan Academy of Sciences, Baku. Translated from Neirofiziologiya, Vol. 24, No. 1, pp. 37–44, January–February, 1992.     

Spatial organization of direct connections of the sensomotor cortex with the rhombencephalon and spinal cord in the cat

The distribution and ultrastructure of terminals of corticofugal fibers in the rhombencephalon and spinal cord of the cat were studied by light and electron microscopy at various times (4–6 days) of experimental degeneration after extensive or local (about 3 mm in diameter) destruction of the sensomotor cortex. Definite topographical organization of corticofugal projections in the nuclei of the dorsal columns and in the spinal cord was detected by the Fink — Heimer method. After local destruction of the lateral zones of the sensomotor cortex, maximal foci of degeneration were found in the nucleus of Burdach and the lateral basilar region of the cervical segments; after local destruction of the medial zones of the sensomotor cortex maximal foci of degeneration of corticofugal fibers were observed in Goll's nucleus and the lateral basilar region of the lumbar segments. The results show that even an extremely localized area of the cat sensomotor cortex forms two separate systems of descending corticospinal fibers. The first projects into the dorsolateral and dorsomedial parts of the intermediate zone, chiefly contralaterally, whereas the second projects bilaterally into both dorsolateral and ventromedial parts of the intermediate zone. The possible physiological significance of this duality of projections is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 2, pp. 126–133, March–April, 1976.     

Electrical activity of thalamocortical association systems in postnatal ontogeny of the cat

Electrical responses to somatic, photic, and acoustic stimulation in the sensomotor, parietal, temporal, and occipital regions of the cortex were studied in the nucleus lateralis posterior and nucleus ventralis lateralis of the thalamus by recording averaged evoked potentials in kittens (aged 3 to 41 days) anesthetized with pentobarbital. A definite order of maturation of afferent inputs into cortical association areas was demonstrated. The parietal cortex was shown to become polysensory before the sensorimotor cortex. It is suggested that the nucleus lateralis posterior is the main thalamic nucleus responsible for conduction of visual information to the cortex in kittens during the first month of life. Incorporation of this nucleus into the system conducting somatic impulsation to the sensorimotor cortex takes place by the age of 3 weeks.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 14, No. 5, pp. 476–482, September–October, 1982.     

Corticofugal influences on postsynaptic processes in rubrospinal neurons in the cat brain

Composite and unitary EPSPs of red nucleus neurons evoked by stimulation of the sensomotor and association parietal cortex and nucleus interpositus of the cerebellum were studied in acute experiments on cats anesthetized with pentobarbital. A monosynaptic connection was shown to exist between not only the sensomotor, but also the association cortex, and rubrospinal neurons, in which unitary EPSPs appeared during stimulation of the association cortex after a latent period of 1.5–2.7 msec, with a peak rise time of 1.1–3.1 msec and an amplitude of 0.22–0.65 mV. Analysis of the temporal characteristics of the unitary EPSP suggested that synapses formed by fibers from the association cortex occupy a position nearer the soma than synapses formed by axons of sensomotor cortical cells.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 16, No. 1, pp. 67–74, January–February, 1984.     

Various types of non-synaptic intercellular contacts in the developing brain of the rat

Peculiarities of ultrastructural organization and localization of early forms of avascular nonsynaptic types of junctions formed in 14-18-day-old rat embryos have been studied; cerebral structures different in their phylogenic relations (the sensomotor cortex and nucleus caudatus) are taken as an example. Five main types of nonsynaptic intercellular junctions have been revealed: desmosome-like, gap, symmetric, asymmetric and mixed junctions. They differ by their ultrastructural organization. These types of junctions make the main types of contacts: soma-somatic, dendro-somatic, dendro-dendritic, axo-somatic, axo-dendritic. Desmosomes form the greatest number of the contacts. The earliest and the most primitive are gap junctions; they, evidently, reflect functional activity of desmosome-like junctions. The mixed junctions, perhaps, reflect the developmental stages of the intercellular contacts of transition from one type of junctions into another. Localization peculiarities of the nonsynaptic intercellular contacts are demonstrated: glomerule-like formations, establishment of numerous contacts looking like a successive chain, and so on. For some other indices a longer period of intercellular contact formation in the nucleus caudatus is noted, comparing the sensomotor cortex, though the latter is a newer structural cerebral formation from the phylogenic point of view.     

Morpho-chemical characteristics of the brain of rats genetically predisposed to catalepsy

Cell organization of the cerebral cortex and striatum has been studied by+light optics and enzymatic activity of neuromediators catabolism--histochemically. In layers III and V of the sensomotor cortex and in the nucleus caudatus the number of neurons per unit area is increased, and their size is decreased. Volume of cytoplasm and nuclei of neurons in both layers is decreased, the latter--to less extent. The total amount of the perineuronal glia in the nucleus caudatus is also decreased at the expense of astroglia. In the cerebral cortex it is equal, but the ratio between astro-++- and oligodendroglia is changed. Acetylcholinesterase activity in the layers III and V of the sensomotor cortex is lower than in the control, while monoamine oxidase activity is kept at the control level. The genetically determined anomalies++ of growth and development of the cerebral cells is supposed to be considered as a structural base of the cataleptic state.     

Unit responses in area 5b of the suprasylvian gyrus to stimulation of the posterior lateral thalmamic nucleus

In response to stimulation of the posterior lateral nucleus in unanesthetized cats immobilized with D-tubocurarine an evoked potential consisting of three components with a latent period of 3–5 msec appeared in area 5b of the suprasylvian gyrus. All three components were reversed at about the same depth in the cortex (1500–1600 µ). Reversal of the potential shows that it is generated in that area by neurons evidently located in deeper layers of the cortex and is not conducted to it physically from other regions. Responses of 53 spontaneously active neurons in the same area of the cortex to stimulation of the posterior lateral nucleus were investigated. A characteristic feature of these reponses was that inhibition occurred nearly all of them. In 22 neurons the responses began with inhibition, which lasted from 30 to 400 msec. In 30 neurons inhibition appeared immediately after excitation while one neuron responded by excitation alone. The latent periods of the excitatory responses varied from 3 to 28 msec. The short latent period of the evoked potentials and of some single units responses (3–6 msec) confirms morphological evidence of direct connections between the posterior lateral nucleus and area 5b of the suprasylvian gyrus. Repetitive stimulation of that nucleus led to strengthening of both excitation and inhibition. Influences of the posterior lateral nucleus were opposite to those of the specific nuclei: the posterior ventrolateral nucleus and the lateral and medial geniculate bodies. Stimulation of the nonspecific reticular nucleus, however, evoked discharges from neurons like those produced by stimulation of the posterior lateral nucleus.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 5, pp. 502–509, September–October, 1973.     

Spectral analysis of the effects of midantan on bioelectric activity of the rat brain]

The influence of midantan in bioelectrical activity of sensomotor cortex, dorsal hippocampus and lateral hypothalamus in the rats in free behavior in wakefulness condition was studied. It was established that midantan influenced the cortex in two phases. In hippocampus there was an increase in absolute power of dominant theta-diapason.     

Response of sensorimotor cortex neurons to weak disturbances of the magnetic field in Wistar rats. Cytochemical study

The influence of weak disturbances (up to 300 microT) of natural magnetic field on the protein metabolism in neurons of sensomotor cortex (layers III and V) in Wistar rats upon learning in a complex maze was studied. It was found that sensomotor neurons were very sensitive to weak disturbances of magnetic field. The protein content increased, while the nucleus-cytoplasm ratio and osmotic state of neurons remained unchanged. The specificity of neuron's reaction manifested itself in a sharp increase of nucleus and cytoplasm dimensions. In associative neurons (layer III), both the nucleus and cytoplasm were involved in the response; in efferent neurons (layer V), only nuclear parameters changed. The variance coefficients of all parameters of protein metabolism in sensomotor neurons, independently of their functional properties, were much higher than in control, which resulted in a wide diversity of cytochemical response.     

Testosterone 5 alpha-reductase in discrete hypothalamic nuclear areas in the rat: effect of castration

The conversion of testosterone into 5 alpha-dihydrotestosterone (DHT) has been studied in different hypothalamic nuclear areas and in the superficial layers of the cerebral cortex of normal and castrated male rats. The tissue fragments utilized in each incubation have been punched from frozen brain sections utilizing calibrated needles. Castration has been performed 12 (short term) and 180 (long term) days before sacrifice. The nuclear areas studied include: the medial preoptic nucleus (MPN), the lateral preoptic nucleus (LPN), the anterior hypothalamic nucleus (AHN), the lateral hypothalamic nucleus (LHN), the posterior hypothalamic nucleus (PHN), the nucleus ventromedialis (HVM), the arcuate nucleus (AR), the median eminence (ME), the nucleus paraventricularis (HPV), the supraoptic nucleus (SO) and the suprachiasmatic nucleus (SC). The possible effect of castration on the 5 alpha-reductase, were assessed in the MPN,LPN,AHN,LHN,PHN and in the cerebral cortex. The results indicate that, in the male rat: 1) the lateral preoptic(LPN) and the lateral hypothalamic nuclei(LHN) possess a 5 alpha-reductase activity higher than that present in the cerebral cortex and in the other hypothalamic nuclei considered; 2)the suprachiasmatic nucleus (SC) apparently possesses a testosterone metabolizing activity lower than that found in any other nervous structures studied so far; 3) castration does not seem to influence the 5 alpha-reductase activity either in the hypothalamic nuclear structures considered or in the cerebral cortex.     

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.     

Formation of "caudate spindles" in the rabbit sensomotor cortex during ontogeny

Electrical activity of the sensomotor and visual areas of the neocortex during stimulation of the caudate nucleus was recorded in young rabbits aged 3–60 days and in adults. Single stimulation of the caudate nucleus was found to cause the appearance of characteristic bursts of spindle-like rhythmic activity ("caudate spindles"), described previously in cats and monkeys, in the adult rabbit cortex. The latent period of the caudate spindle was about 200 msec, its duration 1–3 sec, and the frequency of its oscillations of the order of 12 Hz. Caudate spindles were most marked in the sensomotor cortex of the ipsilateral hemisphere. In rabbits under 10 days old caudate spindles were not found even if the intensity of stimulation was increased many times. Starting from the age of 15 days bursts of rhythmic activity resembling caudate spindles, but with lower frequency (about 8 Hz), longer latent period (up to 350 msec), and also with a higher threshold, appeared in the sensomotor cortex. The definitive type of caudate spindles was established toward the end of the first month of postnatal life, corresponding to the time of formation and complication of conditioned-reflex activity in developing animals.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 1, pp. 11–15, March, 1985.     

Computation of responses to color and brightness differences of neurons in the rabbit lateral geniculate nucleus

Changes in activity of 51 neurons in the rabbit lateral geniculate nucleus evoked by the replacement of eight color and eight achromatic stimuli in pairs were analyzed. It was found that neurons displayed the earliest phasic (within 50-90 ms after the replacement) and tonic response components. The earliest component strongly correlated with differences between stimuli, whereas the tonic component depended on stimuli intensity. Analysis of phasic component revealed two neuronal populations: the first group of cells was specialized for stimuli differentiation only by their intensities, and, and the second group could measure differences in colors and intensities. Neuronal perceptual spaces were reconstructed using the average of the earliest response component as a measure of differences between stimuli. Spaces of 44 neurons (86%) were two-dimensional with brightness and darkness axes. Such neurons had the same structures of space for color and achromatic stimuli. Spaces of 7 neurons (14%) were four-dimensional with two chromatic and two achromatic axes. The structures of perceptual space reconstructed from neurons in the lateral geniculate nucleus were identical to the spaces calculated from the neurons in the primary visual cortex. The structure of the perceptual space reconstructed from neuronal spikes was also similar to space calculated from the N85 visual evoked potential component recorded under similar conditions and to another space reconstructed on the basis of rabbit's instrumental learning. This fact confirmed the general principle of vector coding in the visual system. The tonic component of the most of neurons in the lateral geniculate nucleus showed a linear correlation with changes in intensities, thereby these neurons could be characterized as pre-detectors for cortical selective detectors.     

A cytochemical study of the effect of tuftsin on the enzyme activity in functionally different formations of the brain in rats]

Quantitative cytochemical methods in functionally different rat brain formations (sensomotor cortex, visual cortex, nucleus caudatus, hippocampus) showed the peculiarities of the effect of tuftsin on the activity of some enzymes (the oxidative, neurotransmitter and protein metabolism enzymes) 15 min and 3 days after its single administration. No changes of activity of neurotransmitter metabolism enzymes (monoamine oxidase, acetylcholinesterase) were registered cytochemically. The specificity of the neuro-tropical effect of tuftsin on protein (activity of aminopeptidase and acid phosphatase) and oxidative (activity of glutamate dehydrogenase and glucose-6-phosphate dehydrogenase) metabolism in different functional brain systems is discussed.     

Marked behavioral and biochemical sensitivity to lesion size in the posterior cortex of the rat

Unilateral focal cortical suction lesions of varying diameter from 0.7 to 2.0 mm were made in the right posterior lateral cortex of rats. Only the 1.0 mm lesion size resulted in spontaneous postoperative hyperactivity. This increased activity was accompanied by significantly elevations in substantia nigra and caudate nucleus dopamine concentrations. Other lesion sizes did not effect behavior or brain biochemical concentrations in this fashion. These results suggest a functional organization in this area of posterior cortex which affects both neurochemistry and behavior.     

Altered Resting-State Functional Connectivity of the Frontal-Striatal Reward System in Social Anxiety Disorder

We investigated differences in the intrinsic functional brain organization (functional connectivity) of the human reward system between healthy control participants and patients with social anxiety disorder. Functional connectivity was measured in the resting-state via functional magnetic resonance imaging (fMRI). 53 patients with social anxiety disorder and 33 healthy control participants underwent a 6-minute resting-state fMRI scan. Functional connectivity of the reward system was analyzed by calculating whole-brain temporal correlations with a bilateral nucleus accumbens seed and a ventromedial prefrontal cortex seed. Patients with social anxiety disorder, relative to the control group, had (1) decreased functional connectivity between the nucleus accumbens seed and other regions associated with reward, including ventromedial prefrontal cortex; (2) decreased functional connectivity between the ventromedial prefrontal cortex seed and lateral prefrontal regions, including the anterior and dorsolateral prefrontal cortices; and (3) increased functional connectivity between both the nucleus accumbens seed and the ventromedial prefrontal cortex seed with more posterior brain regions, including anterior cingulate cortex. Social anxiety disorder appears to be associated with widespread differences in the functional connectivity of the reward system, including markedly decreased functional connectivity between reward regions and between reward regions and lateral prefrontal cortices, and markedly increased functional connectivity between reward regions and posterior brain regions.     

Localization of alcohol and aldehyde dehydrogenases in the human spinal cord and brain

Location of aldehyde dehydrogenase (AldDG) and alcohol dehydrogenase (ADG) has been studied in 38 nuclei of the human brain. Neurons with a high AldDG activity predominate in the nucleus of the descending root of the trigeminal nerve, motor nuclei of the craniocerebral nerves (trigeminal, facial, abducent, blocking, sublingual, supraspinal), motor nuclei of the anterior horns of the spinal cord, lateral vestibular nucleus, posterior nucleus of the vagus nerve, pedunculopontine nucleus, superior salivary nucleus, and in the nucleus of Westphal-Edinger-Jacobovich. Neurons with a moderate AldDG activity predominate in the superior olivary complex, nucleus of the lateral loop, parabrachial (pigmented) mesencephalic nucleus and reticular lateral nucleus. A low enzymatic activity is specific for neurons of the pons proper, inferior vestibular nucleus, trapezoid body of the inferior olivary complex, dentate nucleus of the cerebellum, reticular nucleus of the tegmen of Bekhterev's pons and posterior nucleus of Gudden's suture. A high ADG activity is revealed in piriform neurons of the cerebellar cortex. Functional importance of ADG and AldDG activity in the brain is discussed.     

Connections of various fields of the parietal cortex with the caudate nucleus of the cat brain

By means of the light and electron microscopy methods efferent connections of the fields 5a, 5b and 7 with the caudate nucleus have been studied. These fields are predominantly projected to the dorsolateral corner of the middle and posterior head of the caudate nucleus. The fields 5b and 7, unlike the field 5a, give also origin to the fibers, terminating in the central part of the head and in the caudate nucleus body. The electron microscopic investigation proves the monosynaptic nature of the fields 5a, 5b and 7 with the dorsolateral part of the middle and posterior parts of the caudate nucleus head. The parietal cortex gives origin, mainly, to fine myelin fibers (0.665 +/- 0.029), terminating in the part mentioned of the caudate nucleus. These fibers form small terminals (0.310 +/- 0.014 to 0.430 +/- 0.020 mcm) with asymmetrical membranous thickening; these terminals end on the spines (with a poorly expressed spine apparatus) of the dendrites, evidently, of the middle spine cells. Axonal terminals of the parietal cortex form axodendritic terminals extremely seldom. Axospinous synapses on the dendrites of the middle spine cells, situating in the dorsolateral part of the caudate nucleus head are supposed to be a morphological substrate, ensuring the cortical control of the parietal cortex at the level of the caudate nucleus.     

Dynamics of instrumental reflex changes following transection of the corticospinal tract and ablation of the cerebral cortex sensorimotor region in rats

Unilateral transection of bulbar pyramid performed prior to ablation of the ipsilateral sensomotor cortex was shown to facilitate recovery of operant conditioning and compensatory processes in rats. There was no such corticofugal plasticity in ablation of the sensomotor cortex alone. The phenomenon may be explained by switching of descending influences on the cortico-rubrospinal system through participation of the loop: corticorubral projection--red nucleus--inferior olive--cerebellum--thalamus--cerebral cortex.