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.     

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.     

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.     

Convergence of corticofugal impulses on pontine neurons

Convergence of corticofugal impulses in reticular and intrinsic pontine nuclei during stimulation of the frontobasal cortex (proreal, posterior orbital, and basal temporal regions) and also of the dorsal hippocampus was studied in acute experiments on cats anesthesized with a mixture of pentobarbital and chloralose. Three foci of convergence of corticofugal impulses were found in these structures: one in the reticular formation and two in the intrinsic nuclei—in their medial and lateral portions. Neurons with an excitatory type of response were shown to predominate in the reticular formation and neurons with an inhibitory or mixed type of response of neurons activated antidromically by stimulation of one brain region and synaptically during stimulation of another, that the pontine nuclei play an integrative role in the functional unification of structures of the frontobasal zones of the neocortex and hippocampus.M. Gor'kii Donetsk Medical Institute. Translated from Neirofiziologiya, Vol. 12, No. 5, pp. 472–480, September–October, 1980.     

Electrophysiological analysis of corticopontine connections

In acute experiments on cats anesthetized with pentobarbital and chloralose, the method of recording focal responses was used to study projections of various parts of the orbito-frontal and basal temporal cortex and also of the hippocampus in the region of the pons. Different formations of the fronto-basal zones of the neocortex were shown to have local projections in the rostral zones of the pons and relatively diffuse projections in its caudal zones. Projections of the hippocampus in structures of the pons are less well marked than those of the fronto-basal zones of the neocortex and their focal responses are more diffuse in character. Representation of all the structures studied is found only in the nuclei of the gray matter of the pons. The orbito-insular zone of the orbito-frontal cortex is not represented in the caudal zones of the reticular formation; the basal temporal cortex has no projection in the middle cerebellar peduncles.A. M. Gor'kii Donetsk Medical Institute. Translated from Neirofiziologiya, Vol. 9, No. 4, pp. 347–354, July–August, 1977.     

Functional topography of afferent projections of the horizontal division of the nucleus of the diagonal band in the dorsolateral neocortex of the cat

EPs recording under Nembutal anaesthesia during stimulation of the medial section of the horizontal part of the diagonal band nucleus (HNDB) shows a wide spreading of HNDB afferentation over the neocortex: from the frontal area to the medial and some posterior parts of the auditory, parietal areas and Ep zone, with the least activation of the latter three regions and activation increasing intensity correspondingly in the somatic zones II, I (SII, SI), motor and frontal cortex. Such reduction of signals flow intensity oriented both in caudal and ventral directions of the cortex goes with foci of maximal activity of these signals in the motor, parietal areas and zones of representation of various body parts in SI and SII. Traits of similarity and differences of signal's projections in the neocortex from HNDB and thalamic relay nuclei have been revealed. A hypothesis is substantiated on different mechanisms underlying peculiarities of influences of these subcortical nuclei on the cortex depending on the type of their afferent-neuronal links in the latter and their functional role in the brain activity.     

The structural-functional characteristics of the rostral sections of the neocortex in Chiroptera]

Studies have been made on the connections of rostral neocortex in bats in order to reveal connections with the structures of the auditory sensory system the existence of which is indicated by evident specific responses to ultrasound in the form of synchronization reaction. It was shown that dorsolateral parts of the rostral neocortex receive topically organized projections from the thalamic nuclei VPL and VL. Connections with the auditory cortex and suprageniculate nucleus are not evident. Afferents of the medial wall of the rostral cortex originate from the thalamic nuclei MD and AM. Possible pathways of auditory afferentation to the dorso-lateral part of rostral neocortex are discussed.     

大白鼠脚内核的传入性联系

众所周知,肉食动物和大白鼠的脚内核,相当于灵长类的内侧苍白球(Nagy et al.1978;Fox and Schmitz 1944);它们的细胞形态、传入及传出均相同。早期以及近年来的一些研究工作者,虽然在研究其他核团的投射时,联系到一些本核团的传入,但是尚缺乏对本核团传人的系统研究。本实验即是应用辣根过氧化物酶的逆行传递法来研究大白鼠脚内核的传入性联系。     

Auditory processing in primate cerebral cortex.

Auditory information is relayed from the ventral nucleus of the medial geniculate complex to a core of three primary or primary-like areas of auditory cortex that are cochleotopically organized and highly responsive to pure tones. Auditory information is then distributed from the core areas to a surrounding belt of about seven areas that are less precisely cochleotopic and generally more responsive to complex stimuli than tones. Recent studies indicate that the belt areas relay to the rostral and caudal divisions of a parabelt region at a third level of processing in the cortex lateral to the belt. The parabelt and belt regions have additional inputs from dorsal and magnocellular divisions of the medial geniculate complex and other parts of the thalamus. The belt and parabelt regions appear to be concerned with integrative and associative functions involved in pattern perception and object recognition. The parabelt fields connect with regions of temporal, parietal, and frontal cortex that mediate additional auditory functions, including space perception and auditory memory.     

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.     

Cochleotopic organization of the primary auditory cortex in cats

The cochleotopic organization of the primary auditory cortex was studied by the evoked potentials method in cats anesthetized with pentobarbital. Two foci of maximal activity (dorsal and ventral) were found in the primary auditory cortex of 85% of animals during local electrical stimulation of different areas of the cochlea. Analysis of projection maps of the primary auditory cortex of the cats showed that different areas of the cochlea are presented in this region disproportionately. The basal portion projects to a larger cortical surface than the middle and apical portions together, evidence of inequality of representation of different parts of the receptor apparatus of the cochlea in the primary auditory area. Considerable differences were observed in the arrangement of projections of the cochlea in the primary auditory cortex of different animals.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 11, No. 2, pp. 117–124, March–April, 1979.     

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.     

Electrophysiological study of corticocaudate projections in cats

The potential waves evoked in the caudate nucleus (CN) of cats by stimulation of the cerebral neocortex were stereotactically recorded. The head and the body of the caudate nucleus were systematically explored. Stimulation of the ipsilateral sigmoid gyrus and the orbitofrontal cortex evoked waves with the largest amplitude in the CN. Smaller potentials were evoked from the ipsilateral ectosylvian and suprasylvian gyri and from the sigmoid gyrus on the contralateral side. Antidromic conduction from the caudate nucleus to the cortex demonstrated the directness of the corticocaudate pathway. By stimulating the white matter and by making lesions, the corticocaudate pathway was shown to pass, in part, through the subcallosal fasciculus and, in part, through the internal capsule. Corticocaudate connections were shown to be separate from the fibers of the corticospinal tract. A staggered and extensively overlapping topographic progression of the corticocaudate projections was demonstrable along the antero-posterior axis, but was less evident in the medio-lateral direction. It was concluded that the intranuclear distribution of functional synaptic connections must be more profusely branched than was suspected from anatomical data.     

Electrophysiological study of corticocaudate projections in cats.

The potential waves evoked in the caudate nucleus (CN) of cats by stimulation of the cerebral neocortex were sterotactically recorded. The head and the body of the caudate nucleus were systematically explored. Stimulation of the ipsilateral sigmoid gyrus and the orbitofrontal cortex evoked waves with the largest amplitude in the CN. Smaller potentials were evoked from the ipsilateral ectosylvian and suprasylvian gyri and from the sigmoid gyrus on the contralateral side. Antidromic conduction from the caudate nucleus to the cortex demonstrated the directness of the corticocaudate pathway. By stimulating the white matter and by amking lesions, the corticocaudate pathway was shown to pass, in part, through the subcallosal fasciculus and, in part, through the internal capsule. Corticocaudate connections were shown to be separate from the fibers of the corticospinal tract. A staggered and extensively overlapping topographic progression of the corticocaudate projections was demonstrable along the antero-posterior axis, but was less evident in the medio-lateral direction. It was concluded that the intranuclear distribution of functional synaptic connections must be more profusely branched than was suspected from anatomical data.     

Functional Mapping of Dorsal and Median Raphe 5-Hydroxytryptamine Pathways in Forebrain of the Rat Using Microdialysis

Abstract: Recent neurochemical studies of the properties of 5-hydroxytryptamine (5-HT) pathways arising from the dorsal raphe nucleus (DRN) and median raphe nucleus (MRN) have measured extracellular 5-HT in brain regions with reported preferential DRN or MRN 5-HT inputs. Here, we have tested whether electrical stimulation of the DRN and MRN releases 5-HT in rat forebrain regions in a pattern that fits the reported distribution of DRN/MRN pathways. The effect on extracellular 5-HT of electrical stimulation (5 Hz, 300 µA, 20 min) of the DRN, and then MRN, was determined in six regions of the anaesthetised rat. Stimulation of the DRN evoked a short-lasting but clear-cut release of 5-HT (+70–100%) in regions (frontal cortex, dorsal striatum, globus pallidus, and ventral hippocampus) reported to receive a 5-HT projection from the DRN. Regions receiving an MRN innervation (dorsal hippocampus, medial septum, and ventral hippocampus) released 5-HT (+70–100%) in response to MRN stimulation. Regions reported to receive a preferential DRN innervation (frontal cortex, dorsal striatum, and globus pallidus) did not respond to MRN stimulation. Of two regions (dorsal hippocampus and medial septum) reported to receive a preferential MRN innervation, one did not respond to DRN stimulation (dorsal hippocampus) although the other (medial septum) did. In summary, electrical stimulation of the DRN and MRN released 5-HT in a regionally specific pattern. With the exception of one region (medial septum), this pattern of release bears a strong relationship to the distribution of 5-HT projections from the DRN and MRN reported by anatomical studies. The combination of raphe stimulation with microdialysis may be a useful way to study the in vivo neurochemistry of DRN/MRN 5-HT pathways.     

Somatotopic Organization of the Third Somatosensory Area (SIII) in Cats

Multiunit microelectrode recording techniques were used to study the location and organization of the third somatosensory area (SIII) in cats. Representations of all major contralateral body parts were found in a small region of cortex along the lateral wing of the ansate sulcus and between the lateral sulcus and the suprasylvian sulcus. The systematic map of the body surface included forepaw and face regions previously identified as parts of SIII. The forepaw representation was generally buried on the rostral bank of the lateral wing of the ansate sulcus. The representations of the face and mystacial vibrissae were largely exposed on the rostral suprasylvian gyrus, but part of the representation of the face was also buried in the lateral wing of the ansate sulcus. Representations of the trunk and hindlimb extended from the suprasylvian gyrus onto the medial bank of the suprasylvian sulcus. We had expected to find these latter body parts in more medial cortex just caudal to the representation of these parts in the first somatosensory area (SI). Instead, neurons in penetrations in cortex caudal to the SI trunk and hindlimb representations were unresponsive to tactile stimulation. The unexpected location of the hindlimb in SIII led us to determine whether the proposed parts of SIII had similar cortical and thalamic connections. Injected anatomical tracers revealed that the representations of both the forelimb and hindlimb were interconnected with SI and a region of the thalamus just dorsal to the ventroposterior nucleus. Similarities in patterns of connections of forelimb and hindlimb portions of SIII supported the conclusion that SHI as presented here is a functional unit of cortex. We conclude that SIII has a somatotopic organization that does not parallel that in SI, and that SIII is not entirely coextensive with either area 5 or area 5a of Hassler and Muhs-Clement (1964).     

Some morphological and functional properties of the lateral line system of the dwarf catfish

The peripheral and central portions of the lateral line system of the dwarf catfish were studied by morphological and electrophysiological methods. The posterior lateral line nerve, innervating the electro- and mechanoreceptors of the trunk, was shown to consist of poorly myelinated fibers 2–9 µ in diameter. The conduction velocity in this nerve varied from 10 to 15 m/sec. The lateral line nerves end in the medial nucleus of the acoustico-lateral region, which consists of dorsal and medial parts. The former is composed of circular and triangular cells measuring 6–14 µ, the second part by circular cells measuring 4–6 µ. These parts of the medial nucleus are most sharply differentiated in the region of entry of the auditory nerve. Responses to stimulation of the lateral line electro- and mechanoreceptors were recorded over the whole of the acousticolateral region in the caudal-rostral direction. The neurons studied were located at depths of 400–800 µ in the region of the medial nucleus.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad, Translated from Neirofiziologiya, Vol. 7, No. 2, pp. 203–207, March–April, 1975.     

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.     

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.     

Change in the functional significance of structures of the cat brain as a result of reorganization of its activity

A study was carried out on 8 adult cats of functional role of the frontal, parietal and occipital parts of the neocortex, and also of the dorsal hippocampus, mediodorsal thalamic nucleus and caudate nucleus head, in realization of a delayed spatial choice (DSCh) before and after compensatory reorganizations of the brain activity caused by multiple electrical stimulation of the frontal part of the cerebral cortex. Compensatory reorganization led to a change of functional significance of these structures. While before this change the frontal cortex, hippocampus and mediodorsal thalamic nucleus were critically necessary brain areas for the realization of the DSCh, after it parietal and occipital cortical areas acquired such significance. The obtained data are discussed proceeding from the principle of the integrity in the brain activity.