Connections between the parietal cortex with the lateral suprasylvian gyrus (Clare-Bishop area) and auditory cortex in cats

Projections between areas 5 and 7 and the lateral suprasylvian gyrus (Clare-Bishop area) were investigated using anterograde degeneration techniques. This showed a topographic organization of projections from areas 5 and 7 to the lateral suprasylvian gyrus. Area 5 association fibers terminate mainly in the anterior portion of the lateral suprasylvian gyrus; this corresponds to the intermediate zone and anterior section of the posterior suprasylvian region. Area 7 efferents are located more caudally, terminating in the posterior section of the intermediate zone and in the posterior region, excluding the outer posterior limits. Fields 5 and 7 give rise to single efferent fibers terminating in the auditory cortex. Fibers from area 5 terminate in the medial ectosylvian and medial, sylvian gyri, i.e., in zones Al and AII or areas 22 and 50. A projection from area 7 terminates at the superior border of the medial ectosylvian gyrus, corresponding to the upper limit of zone A1 or areas 22 and 50.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 22, No. 6, pp. 739–745, November–December, 1990.     

Facilitating action of medial prefrontal cortex upon the noxious thermally-evoked responses in thalamic centralis lateralis nucleus.

This paper shows a medial prefrontal cortex (CxAP9) facilitating influence upon the unit activity of the centralis lateralis (Cl) nucleus of the thalamus, in rats anesthetized with urethane. Cortical influences were studied using both cortical cooling and cortical spreading depression (CSD) procedures. Both spontaneous and noxious thermally evoked activities were considered. When CSD was propagated and affected the CxAP9, as well as during the cooling of this area, both spontaneous activity and the responses evoked in Cl cells by noxious stimulation were blocked. This effect was interpreted as a cortical disfacilitation upon Cl cells. During the cortical silent period we tested the excitability of a few Cl cells, provoking their activation by passing electrical current across the same Cl recording electrode. No changes were observed in their excitable response threshold during CSD or cortical cooling. Our results are in agreement with the proposition of a tonic cortical facilitatory action upon the spontaneous and noxious-evoked responses recorded in the Cl cells.     

Unit responses in the posterior suprasylvian gyrus of cats to different stimuli

Extracellular responses of 151 spontaneously active neurons in a small area of the cortex of the posterior suprasylvian gyrus to flashes, clicks, and electrodermal stimulation were studied in unanesthetized cats immobilized with D-tubocurarine. Altogether 63% of neurons responded to the stimuli, of which flashes were the most effective. The proportions of polybi-, and monosensory responding neurons were 60, 18, and 22% respectively. Responding neurons were found throughout the thickness of the cortex, but most frequently at depths of 1000–2000 µ from the brain surface. The latent periods varied not only for different cells (from 20 to 90 msec to all stimuli), but also for the same cell. Responses were unstable, prolonged (over 1 sec) and complex in their dynamic pattern (several phases of increase and decrease in frequency of spontaneous discharges or merely a prolonged increase or decrease in its frequency). In the character of their responses the neurons were divided into 4 groups: 1) poly- and bisensory with equivalent responses to all stimuli; 2) poly- and bi-sensory with nonequivalent responses; 3) monosensory, and 4) nonresponding. The results show that this area of the posterior suprasylvian gyrus is part of the associative cortex with projection predominantly of the visual receptor.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 4, pp. 375–383, July–August, 1972.     

The mechanism of interaction between the thalamic posterior lateral nucleus and the sensomotor cortex in rabbits

The thalamic posterior lateral nucleus was shown to exert phasic and tonic effects on the function of sensomotor cortex: the former in the form of pulvinar-cortical responses, and the latter in the form of foci of increased or decreased excitability. The findings suggest an inhibitory tonic effect of the sensomotor cortex on neuronal network of the posterior lateral nucleus.     

Connections of neurons of the cat somatosensory cortex with the thalamic relay nuclei

Of 103 neurons in the rostral part of the posterior sigmoid gyrus of the cat cortex 30 responded to stimulation of the ventro-posterolateral and ventrolateral nuclei of the thalamus (VPL and VL), 42 responded to stimulation of VL only, and 31 to stimulation of VPL only. It was shown by intracellular recording that stimulation of VPL induces a spike response with or without subsequent IPSPs in some neurons and an initial IPSP in others. The spike frequency of single neurons reached 60/sec, but the IPSP frequency never exceeded 10–20/sec. Stimulation of VL was accompanied by: a) antidromic spike responses; b) short-latency monosynaptic EPSPs and spikes capable of following a stimulation frequency of 100/sec; c) long-latency polysynaptic EPSPs and spikes appearing in response to stimulation at 4–8/sec; d) short-latency IPSPs; e) long-latency IPSPs increasing in intensity on repetition of infrequent stimuli. It is concluded that the afferent inputs from the relay nuclei to neurons of the somatosensory cortex are heterogeneous. An important role is postulated for recurrent inhibition in the genesis of the long-latency IPSPs arising in response to stimulation of VL, and for direct afferent inhibition during IPSPs evoked by stimulation of VPL. It is shown that the rostral part of the posterior sigmoid gyrus performs the role of somatic projection and motor cortex simultaneously.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 3, pp. 245–255, May–June, 1972.     

Neuronal populations in the posterior group of thalamic nuclei projecting to the amygdala and auditory cortex in cats

Neuronal populations which are sources of fiber tracts to the amygdala and auditory cortexin the posterior group of thalamic nuclei and adjacent structures of the cat mesencephalon were studied by the retrograde axonal transport of horseradish peroxidase method. It was shown that the peripeduncular, suprageniculate, and subparafascicular nuclei form numerous projections to the amygdala. In all parts of the posterior group of thalamic nuclei, common zones of localization of sources of ascending pathways into the amygdala and auditory cortex were demonstrated. A powerful source of projections to the amygdala from the caudal part of the medial geniculate body was discovered.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 213–224, March–April, 1984.     

Chemical stimulation of the thalamic reticular nucleus inhibits the neuronal activity of the posterior insular cortex in rats

Extracellular neuronal responses were recorded from the posterior insular cortex following electrical and chemical stimulation of the thalamic reticular nucleus (Rt) regions. In the present study, most neurons (29/32) were first characterized for their responses to electrical stimulation of the superior laryngeal (SL) nerve or glossopharyngeal (IXth) nerve. In the first experiment, 15 neurons in the posterior insular cortex were examined for their responses to electrical stimulation of the Rt regions. It was found that effective stimulation sites to evoke action potentials in the posterior insular cortex were the ventromedial portion of the Rt and its adjacent regions. In the second experiment, 17 neurons in the posterior insular cortex were examined for their responses by pressure injection of glutamate (Glu) into the Rt regions. Of the 17 neurons, 13 were inhibited in the spontaneous discharge rate following injection of Glu into the Rt, and the remaining four were unaffected. Histologically, it was demonstrated that Glu injection sites for the case of inhibition were located near or within the Rt. On the other hand, the injection sites for all four non-responsive neurons were located outside of the Rt. These data suggest that excitation of the Rt (GABAergic neurons) causes depression of the neuronal activity in the thalamic relay nucleus and then this may in turn induce depressed neuronal activity in the posterior insular cortex. The results here indicate that neuronal activity in the posterior insular cortex is controlled by the Rt, which has been reported in other sensory systems.     

Retinotopic organization of the posterior suprasylvian area of the feline cerebral cortex

Representation of the visual field was investigated in the feline posterior suprasylvian area (PSA) using electrophysiological mapping techniques. The PSA is one of the extrastriatal visual structures of the cerebral cortex. The PSA retinotopic organization pattern was also studied. Neuronal receptive fields (RF) were mainly located in the upper contralateral quadrant and just a small number in the lower contralateral quadrant of the visual field. Approximately 10% of RF were located in the upper ipsilateral quadrant. The central area of the visual field extending in a radius of 20–30° from the area centralis was mainly represented in the upper section of the PSA (areas 21a and 21b). The RP of neurons located more peripherally to the area centralis are found in the lower portion of the PSA (areas 20a and 20b); these occupy a correspondingly greater area. Experimental finding did not confirm any substantial differences in the retinotopic organization of areas 21a, 21b, 20a, and 20b comprising the PSA. Data obtained would tend to indicate that the PSA consists of two areas, 21a and 21b, which do not appear to be subdivided, with more densely distributed visual neurons in the former than in the latter.Institute of Experimental Biology of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 23, No. 3, pp. 290–296, May–June, 1991.     

Efferent connections of various parts of the orbitofrontal cortex with thalamic structures in cats

By means of impregnation methods of Fink-Heimer and Kawamura-Niimi in 29 cats after unilateral extirpation of various parts of the orbitofrontal cortex (middle part, superior and inferior areas of the dorsolateral part of the proreal gyrus, anterior area of the orbital gyrus) connections with various groups of the thalamic nuclei have been studied. Essential differences have been revealed in projections of various parts of the orbitofrontal cortex to specific, nonspecific, associative and limbic nuclei of the thalamus. The most distributed system of the subcortical projections has the orbital gyrus cortex. Connections of the cortex in the superior and inferior areas of the dorsolateral part of the proreal gyrus are well manifested, the connections of the superior area being less prevalent than the inferior ones. The cortex of the medial part in the proreal gyrus has connections mainly with the subcortical limbic formations. Thus, the orbitofrontal cortex in the cat possesses a system of topographically organized, to some extent selective monosinaptic connections practically with all nuclear groups of the thalamus and influences upon the function of the most of the important subcortical structures.     

Connections of field 17 of the visual cortex with the mammillary nuclei in cats]

Using optical techniques by Nauta--Gygax, Wiitanen and Eager, degenerating nerve fibres and terminals were demonstrated to be present in the hypothalamic mammillary nuclei 9 days after a part of field 17 of the brain cortex was extirpated. Electron microscopic examination revealed different changes in large and small terminals of the boutons 5, 7 and 11 days after similar operations. The data represented demonstrate direct monosynaptic bilateral connections in field 17 of the optic cortex with the hypothalamic mammillary nuclei in cats. They are realized by fine fibrillae terminating mainly in large terminal boutons which form synapses on big and small dendritic branches. Thus, there is a structural base for the immediate influence of the optic cortex on the posterior hypothalamus.     

Unit responses in area 5b of the suprasylvian gyrus to stimulation of the ventral posterolateral thalamic nucleus

Unanesthetized cats were immobilized with D-tubocurarine. Single unit responses in area 5b of the suprasylvian gyrus to stimulation of the ventral posterolateral thalamic nucleus were recorded extracellularly. Of the total number of neurons tested, 32% were excited and 3% inhibited. In 65% of neurons the responses were mixed, most of them being predominantly excitatory. Repetitive stimulation of the ventral posterolateral nucleus (6–9/sec) frequently intensified the excitatory component of the responses. Sometimes inhibition, present in the response to a single stimulus, was replaced by increased excitation. However, the same response as to a single stimulus frequently appeared in response to each consecutive stimulus of a series. Stimulation of the ventral posterolateral nucleus had a mainly excitatory effect on neurons in area 5b. Stimulation of the dorsal lateral nucleus, on the other hand, inhibited their activity. This antagonism could also be observed on the same neuron. It was concluded from the short latent periods of the orthodromic responses (3–6 msec) and from the antidromic responses of the cortical neurons to stimulation of the ventral posterolateral nucleus that this nucleus has direct two-way connections with the cortex of area 5b.     

Generation of ventralized human thalamic organoids with thalamic reticular nucleus

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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.     

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.