Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Neuronal Connectivity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,351 records · Page 75Linked to original sources
PubMedDate not supplied

[Effect of interrupting hippocampal connections on the neuronal activity of several midbrain nuclei].

Experiments were performed on unanaesthetized rabbits with intact brain and with septo-hippocampal disconnection depriving midbrain structures of descending hippocampal influences. General characteristics of neuronal reactions in midbrain raphe (MR) and ventral tegmental nucleus (VT) did not change following deafferentation. The level of reactivity increased in VT and decreased in MR. The mean latencies of on-responses in MR became longer (15,5 msec for auditory stimuli versus 10,5 msec in intact brain); in VT they became shorter (14,5 msec versus 17 msec). Habituation of reactions, normally present in about half of neurones, disappeared. Neurones with incremental responses gradually increasing in strength and duration were observed. Complex functional relations between the hippocampus and unspecific midbrain structures are discussed.

Animals↗
PubMed1984

[Arrangement and afferent connections of the neurons in the visual cortex differing in the size of the receptive fields].

In the area 17 of the cerebral cortex of guinea pigs cells with small and medial receptive fields (RF) are concentrated at the sites of separate groupings of neurons excited by flashes of diffusion light. There are also cells with large RF here. At such sites of the cortex when specific afferents are electrically stimulated many cells exhibit monosynaptic activation irrespective of their RF size. The main part of the neurons with large RF is situated in the areas of the cortex between the excited grouping and monosynaptical excitation is not inherent in such neurons. Most cells of these areas are not excited by specific afferents.

Afferent Pathways↗
PubMed1980

[Structural organization of the synaptic connections of developing neurons in the anterior horns of the spinal cord in early human fetuses].

Synaptogenesis in the presumptive anterior horns of the spinal cord in early human fetuses (weeks 11 -- 12 of intrauterine development) was studied by electron microscopy. In this period of human nervous system development, various stages of the synaptic contact forming process were elucidated in the region under study: from the growth cone attachment to the neuroblastic surfaces up to mature synapses. The appearance of the first synaptic complexes provides evidence of the presence of the high-functional specialization of the synaptic apparatus in the course of differentiation of motoneurons of the spinal cord in the early stages of human antenatal ontogenesis.

Cell Differentiation↗
PubMed1995

[Synaptic connections between the neurons and catecholaminegic fibres in the hippocampal transplant of rat].

The foetal hippocampal tissue (transplant) at 17th day of embryonic age was implanted into the ventral hippocampus of adult rats (host). The catecholaminergic fibre projections in the hippocampal transplants 90 days after operation were studied by immunohistochemical technique. It was observed that in the host hippocampus there was a large population of TH- immunoreactive slender fibres of only 0.5-1 microns in diameter. These fibres were distributed more densely in the hippocampal hilus and CA3 transparent layers than in molecular layers, but sparsely in pyramidal or granular layers. In the molecular and cellular layers of transplanted hippocampus some thicker (> 1 micron) TH-positive fibers were ended in a relatively dense branching. The immunoelectron-microscopic observations showed that many TH-positive boutons made synaptic contacts with immunonegative dendrites and dendritic spines in the hippocampal transplants, the majority of which were asymmetrical synapses with a 30 nm synaptic cleft and conspicuously thickened postsynaptic membranes. It is concluded that catecholaminergic fibres extend from the host brain into the hippocampal transplant to establish synapses with the target neurons.

Animals↗
PubMed1976

[Proceedings: Psychotropic effects of hypothalamic hormones: immunohistochemical indentification of extrahypophyseal connections of neuroendocrine neurons].

Vasopressin (VP) can be shown to exert psychotropic effects independent of its antidiuretic activity, facilitating learning and consolidation of memory in rats. Immunoreactive VP and neurophysin (NP) are localized on serial section of Bouin fixed, paraffi embedded guinea pig, rat and hamster brains. Localization was not restricted to the classical sites of supraoptic and paraventricular nucleus, medianeminence and neurohypophysis...

Animals↗
PubMed1998

[Monosynaptic transmission between mesodiencephalic neurons and motoneurons innervating extraocular inferior oblique muscle in cats].

The present study was performed to define the synaptic connection of neurons located within the dorsal mesodiencephalic junction with motoneurons innervating extraocular inferior oblique muscle (IOMN) using electrophysiologic, especially spike-triggered averaging technique in cats. In response to electric shocks applied to the medial part of Forel's field H (FFH) located in the mesodiencephalic junction, excitatory monosynaptic field potentials were observed in the IOMN pool. Moreover, while the spontaneous discharges of FFH neurons were used to trigger the activity of IOMN pool from which the induced potential changes were averaged, an excitatory monosynaptic field potential was also obtained. These results indicate that the mesodiencephalic neurons connect with and activate the IOMNs monosynaptically, and drive vertical eye movements via such a way.

Action Potentials↗
PubMed1996

Specificity in the axonal connections of layer VI neurons in tree shrew striate cortex: evidence for distinct granular and supragranular systems.

Pyramidal neurons in layer VI of striate cortex are the source of descending projections to the lateral geniculate nucleus (LGN) as well as a major source of axon terminals in the layers of striate cortex that receive LGN projections. This study examines how the connections of layer VI neurons are arranged with respect to the functionally distinct classes of neurons that compose their cortical and subcortical targets. By placing injections of biocytin into layer VI of tree shrew striate cortex, we identified two sublayers that differ in their intracortical and thalamic connections. Neurons in the upper part of layer VI, layer VIa, terminate in cortical layer IV, whereas those in the lower part of layer VI, layer VIb, terminate throughout the supragranular layers, layers I-III. The selectivity of layer VI subdivisions for the granular and supragranular layers is also evident in their descending projections. Neurons in layer VIa terminate preferentially in the LGN layers that supply layer IV (LGN layers 1, 2, 4, and 5), whereas neurons in layer VIb terminate in the LGN layers that supply layers I-III (LGN layers 3 and 6) and in the pulvinar nucleus. Additional subclasses of layer VIa neurons were identified based on the restriction of their terminal fields to narrow subtiers within layer IV. By influencing the activity of distinct populations of cortical neurons and the thalamic neurons that supply them, layer VI neurons could exert a powerful influence on the flow of activity in functionally distinct cortical circuits.

Animals↗
PubMed2005

Cell death or survival: molecular and connectional conditions for olivocochlear neurons after axotomy.

We aimed to determine whether rat olivocochlear neurons survive axotomy inflicted through cochlear ablation, or if they degenerate. To estimate their intrinsic potential for axonal regeneration, we investigated the expression of the transcription factor c-Jun and the growth-associated protein-43 (GAP43). Axonal tracing studies based on application of Fast Blue into the cochlea and calcitonin gene-related peptide immunostaining revealed that many, but not all, lateral olivocochlear neurons in the ipsilateral lateral superior olive degenerated upon cochleotomy. A decrease of their number was noticed 2 weeks after the lesion, and 2 months postoperative the population was reduced to approximately one quarter (27-29%) of its original size. No further reduction took place at longer survival times up to 1 year. Most or all shell neurons and medial olivocochlear neurons survived axotomy. Following cochleotomy, 56-60% of the lateral olivocochlear neurons in the ipsilateral lateral superior olive were found to co-express c-Jun and GAP43. Only a small number of shell and medial olivocochlear neurons up-regulated c-Jun expression, and only a small number of shell neurons expressed GAP43. Up-regulation of c-Jun and GAP43 in lateral olivocochlear neurons upon axotomy suggests that they have an intrinsic potential to regenerate after axotomy, but cell counts based on the markers Fast Blue and calcitonin gene-related peptide indicate that this potential cannot be exploited and degeneration is induced instead. The survival of one quarter of the axotomized lateral olivocochlear neurons and of all, or almost all, shell and medial olivocochlear neurons appeared to depend on connections of these cells to other regions than the cochlea by means of axon collaterals, which remained intact after cochleotomy.

Animals↗
PubMed1976

[Regulation of respiration under conditions of inhibition of carbonic anhydrase activity by diamox].

The functional state of the respiratory center and the mechanism of increase in pulmonary ventilation before and after inhibition of activity of carbonic anhydrase by diamox were studied in anesthetized cats. During the inhibition, activity of bulbar inspiratory neurons functionally connected with motoneurons of the diaphragm was markedly reduced and that of the neurons connected with motoneurons of intercostal muscles was sharply increased. A steady thoracic respiration occurred. The aferents from the carotid sinus nerve and vagus nerve did not affect the steady thoracic respiration. Increased efferent influence upon the intercostal muscles led to forced thoracic respiration which ensured a high pulmonary ventilation during the whole period of action of the diamox.

Acetazolamide↗