Involvement of thalamic neurons and the striopallidal complex in maintaining constancy of visual perception in the human brain

Neuronal activity was investigated in different thalamic nuclei and the striopallidal complex in parkinsonian patients with long-term implantation of intracerebral electrodes in the structures concerned for diagnostic and therapeutic purposes. Directionally selective neurons were found with consistent response to presentation of visual stimuli oriented at the same angle in a variety of (spatial) head positions differing by 90°.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 21, No. 1, pp. 93–101, January–February, 1989.     

Horseradish peroxidase-positive neurons of nonspecific thalamic nuclei projecting to the primary somatosensory cortex in cats

The morphology and topography of neurons whose axons form the nonspecific thalamic input in the primary somatosensory area were studied in the cat forebrain by the retrograde axonal horseradish peroxidase transport method. Stained cells were found in the dorsolateral part of the nucleus ventralis anterior, and were diffusely distributed in the nucleus centralis, lateralis, the lateral part of the nucleus dorsalis medialis, and the dorsal part of the centrum medianum. In the nucleus paracentralis only solitary, palely stained neurons were detected. Cells stained with horse-radish peroxidase were multipolar, triangular, or fusiform. The results are evidence that besides the ventrobasal complex, the nonspecific nuclei of the diencephalon also project into the somatosensory cortex. This indicates the existence of multiple afferent thalamic inputs into the somatic cortex.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 11, No. 5, pp. 435–440, September–October, 1979.     

Connections between presumed diencephalic nuclei of the lizard limbic system using horseradish peroxidase axonal transport technique

Connections between the anterior thalamic and habenular nuclei were investigated in the lizard by administering horseradish peroxidase to these nuclei. They were shown to have overlapping locations of afferent sources, namely basotelencephalic structures, nuclei of anterior and hippocampal commissures, preoptic and lateral hypothalamic area, and superior raphe nucleus, as well as common projection zones, viz: the mamillary complex and the ventral tegmental area. Specific connections confined to individual nuclei were discovered, apart from those common to the nuclei: A reciprocal connection with the dorsolateral hypothalamic nucleus (for the anterior dorsolateral nucleus), a projection to the interpeduncular nucleus (for the habenular nucleus), and to the dorsal hypothalamic area (for the dorsomedial nucleus). No sources of afferent pathways to the anterior thalamic nuclei were found in the mamillary complex. All the thalamic nuclei studied, togetherwith their connections, are considered diencephalic relay links in pathways comparable with the dorsal (in the case of the habenular nuclei) and the ventral (with respect to the anterior thalamic nuclei) pathways of the mammalian limbic system.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 19, No. 1, pp. 110–120, January–February, 1987.     

Selectivity in the response of human cerebral neurons to visual stimuli at different angles of alignment

The neuronal activity of different nuclei of the thalamus and striopallidar complex was investigated in Parkinsonian patients with intracerebral electrodes chronically implanted in these structures for diagnostic and therapeutic purposes. Neuronal populations were discovered responding differently to the presentation of stimuli identical in all but angle of presentation, some of which responded solely to a single orientation and might therefore be thought of as displaying directional sensitivity. It is suggested that when motor and visual information converge within the above systems, a matching process takes place, together with an interaction relating to stability of visual perception.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad; Institute of Information and Automotive Sciences, Academy of Sciences of the USSR, Leningrad. Translated from Neirofizologiya, Vol. 19, No. 1, pp. 3–11, January–February, 1987.     

Neural connections of the lizard septum investigated by HRP axonal transport techniques

Neuronal connections were investigated in the lizard (Ophisaurus apodus) by injecting horseradish peroxidase. Reciprocal connections were found between the septum and the dorsal and mediodorsal cortex, as well as projections from the diagonal bundle nucleus and the anterior dorsolateral and dorsomedial thalamic nuclei to the septum. The most clear-cut bilateral connections were observed between the septum and the preoptic region, the hypothalamic periventricular structures, and the lateral hypothalamic region (containing dopaminergic neurons) as well as nuclei of the mamillary body. Some characteristics and the overall organization pattern of connections between the septum and other limbic system structures are reviewed.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 20, No. 3, pp. 398–407, May–June, 1988.     

Neurons of the thalamic ventrobasal complex,labeled with horseradish peroxidase,projecting to the primary somatosensory cortex in cats

The morphology and localization of neurons of the thalamic ventrobasal complex projecting to the primary somatosensory cortex were studied in cats by the retrograde axonal transport of exogenous horseradish peroxidase method. Different types of neurons were detected: triangular, round with symmetrical processes, oval with processes diverging asymmetrically, and fusiform. Tagged neurons were distributed as two large populations in the central region of the complex adjoining the boundaries of the two nuclei. Comparison with the somatotopic map showed that the tagged neurons were concentrated mainly in the projection area of the forelimb and head. Since microinjections of peroxidase into the somatosensory cortex also were given in the projection areas for the forelimb and head, the results confirm the neurophysiological concept of strict somatotopic organization of thalamocortical input.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. A. A. Ukhtomskii Physiological Institute, Leningrad. Translated from Neirofiziologiya, Vol. 11, No. 2, pp. 125–129, March–April, 1979.     

Response of recticular and dorsal thalamic nuclei neurons during extinction of conditioned implementation in the cat

Unit activity in 66 neurons of the reticular (R) nucleus and 31 neurons of the ventropostrolateral nuclei of the thalamus, and 14 neurons of the posterolateral nuclear complex, the pulvinar, were studied during extinction of the conditioned food implementation reflex. The number of R neurons that had responded to initial excitation in the first 300 msec after the conditional stimulus (CS) decreased with the extinction. Simultaneous disappearance of conditioned-reflex placement movements and late excitatory and inhibitory responses of R and dorsal thalamic nuclei neurons with latent periods exceeding 300 msec was also observed. Extinction of the conditioned reflex (CR) led to a significant lowering of background activity in two-thirds of investigated R and other thalamic nuclear neurons. This suggests that efferent effects from the reticular nucleus are decreased during Cr extinction.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the USSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 1, pp. 3–8, January–February, 1991.     

Localization of sources of thalamic inputs into the sensorimotor cortex in the rabbit using retrograde axonal transport technique

It was shown that the rabbit sensorimotor cortex received afferent fibers from neurons located in the specific, nonspecific, and association thalamic nuclei using the retrograde axonal transport technique. The distribution, dimensions, and shape of the somata of relay neurons spread through the thalamic nuclei were analyzed. The total number of neurons sending out thalamo-sensorimotor-cortical fibers was calculated and the coordinates of loci with the highest density of these cells in each thalamic nucleus were identified. Multipolar and stellate cells with somata measuring 12–20 µm and 10–15 µm in diameter, respectively, prevailed amongst relay neurons. Amongst the specific nuclei, the majority of afferent fibers are sent out by the ventrolateral, ventral anterior, and anterior ventral nuclei. A comparable number of afferent fibers are sent out by the mediodorsal and paracentral nuclei; these split up among the association nuclei and paracentral nuclei, respectively. It is suggested that afferents from many different groups of thalamic nuclei are essential for the sensorimotor cortex to participate in thalamocortical interaction.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 19, No. 1, pp. 87–94, January–February, 1987.     

Determining neuronal response of the rabbit thermoregulatory center to thermal stimulation

A classification was made of neuronal spike activity in the dorso- and ventromedial hypothalamic nuclei. Thermosensitive neurons in which response was accompanied by change in activity pattern could be identified with 0.95 probability by means of an algorithm based on this classification.I. V. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 20, No. 3, pp. 291–301, May–June, 1988.     

Connections linking the mamillary complex and hypothalamo-tegmental area of the brain with the brainstem in lizards

Connections between the hypothalamus and brainstem formations were investigated inOphisaurus apodus by locally injecting horseradish peroxidase (HP) or lectin-HP into the mamillary complex and the hypothalamo-tegmental area of the brain. Direct reciprocal connections were found linking mamillary complex nuclei and posterior and lateral hypothalamic structures with the following brainstem formations: central gray matter, parabrachial nucleus, raphe nuclei and the lateral loop, reticular formation of the caudal mesencephalon, pons, and medulla. It was concluded that direct bilateral hypothalamo-brainstem connections were already in place in reptiles, serving as the basis for sympatho-emotional nociceptive, and antinociceptive response.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 114–123, January–February, 1990.     

Sources of ascending afferent projections to the midbrain central tegmental area and centrum medianum thalami in cats

After microinjections of horseradish peroxidase into the central tegmental area of the midbrain and centrum medianum thalami in cats, labeled neurons were found in the nucleus of the tractus solitarius, gracile and cuneate nuclei, spinal nuclei of the trigeminal nerve, the external nucleus and nucleus of the brachium of the inferior colliculus, the medial pretectal region, nucleus of the posterior commissure and stratum intermediale of the superior colliculus, and reticular structures of the medulla and pons. Comparison of the location of the sources of ascending afferent projections in the central tegmental area of the midbrain and centrum medianum thalami showed that the reticular formation receives mainly visceral projections through the nucleus of the tractus solitarius, whereas the centrum medianum thalami is innervated mainly by the system of sensory somatic nuclei.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 14, No. 2, pp. 172–178, March–April, 1982.     

Efferent connections of the centrum medianum of the cat thalamus revealed by autoradiography

Efferent connections of the centrum medianum and parafascicular nucleus of the thalamus (CM-Pf complex) in cats were studied by the method of anterograde axonal transport of tritiated amino acids followed by autoradiography. Projections from CM-Pf ascend to nuclei of the ventral group and nonspecific nuclei of the thalamus, preoptic, dorsal, lateral, and posterior areas of the hypothalamus, and also into the subthalamic region. Descending pathways are formed only by neurons of the caudomedial part of CM-Pf. They project into the pretectal region, superior colliculus, reticular formation, locus coeruleus, region of the ramus communicans, and substantia grisea centralis of the mesencephalon and pons, and also into the nuclei raphe, magnocellular reticular area, and inferior olivary nucleus of the medulla. In agreement with previous observations it was found that the caudomedial part of CM-Pf does not send direct projections into the cortex and striatum.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 224–230, March–April, 1984.     

Modular organization of callosal neurons in the rabbit sensomotor cortex

The density of distribution of callosal neurons in the rabbit sensomotor cortex was studied by injecting horseradish peroxidase into the symmetrical region of the cortex. The degree of inequality of distribution of labeled neurons was determined visually and by statistical analysis. Stained callosal neurons were mainly small and medium-sized pyramidal cells, located chiefly in layer III–IV, and substantially less frequently in layers V and VI. Different forms of grouping of labeled neurons were observed in layer III–IV: two cells at a time, five to eight cells arranged vertically, or in concentrations, whose width was usually 120–200µ, and separated by areas with reduced density. The results are regarded as confirmation of those drawn previously from results of electrophysiological investigations on the modular organization of callosal connections in the rabbit sensomotor cortex.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Brain Institute, Academy of Medical Sciences of the USSR, Moscow. I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 451–457, July–August, 1984.     

Differentiation of efferent projections of the medial (cuneiform nucleus) and lateral regions of the reticular formation in cat midbrain

Efferent connections of medial (nucleus cuneiformis) and lateral regions of the midbrain reticular formation (MRF) were investigated using an anterograde autoradiographic technique in cats. Efferent fibers from the MRF ascend to the globus pallidus, substantia innominata, hypothalamus, subthalamus, and nonspecific associative and relay nuclei of the thalamus. Descending pathways to the conclusion that the cuneiform nucleus is more of a nonspecific structure than an association auditory center. The lateral reticular region had numerous projections to the lateral geniculate body and, together with the parabigeminal nucleus, forms the midbrain visual complex.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 17, No. 5, pp. 646–652, September–October, 1985.     

Rubrocaudate projections in the cat

Small numbers of neurons projecting to the caudate nucleus were found in the cat red nucleus using horseradish peroxidase retrograde axonal transport techniques. Rubrocaudate neurons were found in both the parvo- and magnocellular sections of the red nucleus. Organization of reciprocal connections between the red nucleus and the striopallidal system is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 20, No. 1, pp. 28–32, January–February, 1988.     

Evoked potentials in the parafascicular complex of the rabbit thalamus during peripheral noxious stimulation

Systematic research was conducted into the parafascicular complex of the nonspecific nociceptive system of the rabbit hypothalamus using a technique of evoked potentials. Two types of evoked response were recorded during electrocutaneous stimulation of the paw; a compound response consisting of early and late positive-negative potentials in the lateral region and a simple positive-negative evoked potential in the medial area. Evidence suggests a more complex organization of the thalamic parafascicular complex in leporines than previously supposed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 18, No. 6, pp. 787–793, November–December, 1986.     

Diencephalic afferents of the rat hippocampus

Connection between diencephalic structures and the hippocampus were investigated in albino rats by the retrograde horseradish peroxidase axon transport method in albino rats. After injection of horseradish peroxidase into the dorsocaudal zone of hippocampal area CA₁, cells labeled with the enzyme were found in nuclei of the thalamus and hypothalamus. The sources of hippocampal afferents were found to be both nonspecific (n. reuniens, n. centralis lateralis, n. centralis medialis) and specific (n. anterodorsalis, n. anteroventralis, n. lateralis anterior, n. lateralis) thalamic nuclei. Axons to the hippocampus also are sent by neurons of n. paraventricularis and n. perifornicalis of the hypothalamus. The results are evidence that direct pathways from structures with sensory inputs run to the hippocampus from the thalamus.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 13, No. 4, pp. 359–364, July–August, 1981.     

Unit responses of the cat caudate nucleus to cortical stimulation before and after destruction of nonspecific thalamic nuclei

Responses of caudate neurons to stimulation of the anterior sigmoid and various parts of the suprasylvian gyrus were studied in acute experiments on cats. The experiments consisted of two series: on animals with an intact thalamus and on animals after preliminary destruction of the nonspecific thalamic nuclei. Stimulation of all cortical areas tested in intact animals evoked complex multicomponent responses in caudate neurons with (or without) initial excitation, followed by a phase of inhibition and late activation. The latent periods of the initial responses to stimulation of all parts of the cortex were long and averaged 14.5–25.5 msec. Quantitative and qualitative differences were established in responses of the caudate neurons to stimulation of different parts of the cortex. Considerable convergence of cortical influences on neurons of the caudate nucleus was found. After destruction of the nonspecific thalamic nuclei all components of the complex response of the caudate neurons to cortical stimulation were preserved, and only the time course of late activation was modified.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 5, pp. 464–471, September–October, 1980.     

Frequency characteristics of skate electroreceptive central neurons responding to electrical and magnetic stimulation

Responses of single neurons in the lateral lobes of the medulla to stimulation of the electroreceptive system by homogeneous sinusoidal electrical and magnetic fields were investigated in acute experiments on the skateRaja radiata. Thresholds of neuronal responses to electrical stimulation varied from 0.03 to 10 µV/cm. The optimal frequency ranges for electrical and magnetic reception were in the regions of 0.05–5 and 2–3 Hz respectively. The possible mechanisms and functional significance of frequency characteristics of central neurons are discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. All-Union Cardiologic Scientific Center, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 464–470, July–August, 1984.     

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.