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N M Ipekchian

Publications and source records attributed to N M Ipekchian.

12 recordsLinked to original sources
PubMed2005

[Quantitative characteristics of the cortex area 4y associative projections to subfields of the sensomotor and parietal cerebral cortex in cat].

The ipsilateral association connections of the motor cortex area 4y after its local electrolytic lesion in the cat were studied using Nauta-Gigax method. Relative quantitative distribution of the efferent association fibers projecting from area 4y to the somatosensory regions I and II, motor and parietal cortex, was determined. It was shown that the major projections from area 4y are directed to area 2pri (secondary somatosensory zone) and to area 5ab. Sparse degenerating fibers were found in the areas 1, 2, 3a and 3b of the primary somatosensory cortical zone. No efferent fibers were traced projecting from area 4y to the areas 4fu, 4sfu, 6aa, 6ab and 6ifu. It is suggested that the morphological basis of the motor reactions implemented by area 4y is formed not by fundal (4fu, 4sfu, 6ifu) or premotor (6aa, 6ab) subfields, but by the areas 2pri and 5ab which are involved to a maximum degree.

Animals↗
PubMed2000

[A comparative analysis of the descending projections of areas 5 and 7 of the parietal cortex to the cat brain stem].

Relative quantity of descending fibres of parietal fields 5 and 7 of cat brain stem was studied. Maximal projections of these field were determined, maximal projections of fields 5 and 7 to red nucleus reticular nucleus of midbrain and nucleus proprius of pons were shown. Topographic and quantitative overlapping of projections of fields 5 and 7 in red nucleus and reticular nucleus of midbrain was noted. Field 5 is maximally presented in ventral nucleus while field 7 has maximal number of projections in lateral nucleus. Projection of fields 5 an 7 to superior colliculus of tectum of the midbrain was determined that was significant although less pronounced than in the above mentioned nuclei. The number of fibres projecting onto the superior colliculus of tectum of the midbrain (its caudal part) from field 7 exceeds that from field 5. There are less fibres in inferior colliculus of tectum of the midbrain than in superior colliculus. The number of fibres projecting from field 5 is greater than those from field 7 in inferior colliculus. In caudal reticular nucleus of pons the presence of fields 5 and 7 was not significant. Comparison of the authors' data with that available in literature allows to suggest the possible inhibitory, i.e. modulating influence of parietal cortex on nuclei of the pons.

Animals↗
PubMed1990

[The connections of the parietal cortex with the lateral suprasylvian gyrus (the Clare-Bishop field) and the auditory cortex in the cat].

It has been shown that a parietal projection to the Clare--Bishop area is moderate and organized in a topographic manner. Associative fibres of area 5 terminate in the anterior part of the Clare--Bishop area, which corresponds to the intermediate and anterior part of the posterior suprasylvian sulcus belt. Area 7 projects to the posterior part of the intermediate and posterior suprasylvian sulcus belt. Area 5 and 7 send a few fibres to the auditory cortex. Associative fibres of area 5 terminate in the middle ectosylvian and sylvian gyri: areas 22, 50. Area 7 is connected only with the superior extremity of the middle ectosylvian gyrus or of areas 22, 50.

Afferent Pathways↗
PubMed1988

[Projections of fields 5 and 7 in the subdivision of the sensorimotor area of the cat cerebral cortex].

Projections of the parietal cortex (area 5 and 7) to the subdivisions of the sensorimotor cortex have been studied with axonal degeneration method. It was shown that density of distribution of the association fibres is different in the areas of the parietal and sensorimotor cortex. Area 5 projects mainly to the posterolateral part of the cruciate sulcus (areas 4fu, 4 delta); its projections to areas 4y, 4sfu and 6iffu, 6aa, 6ab are less pronounced. Area 7 is connected mostly with the medial part of the lower lip of the cruciate sulcus (areas 6iffu, 6aa, 6ab) and its projection to areas 4fu and 4 delta is less pronounced. Poor interrelation between area 5 and areas SI (2, 3a, 3b) and no projection to SII (second somatosensory area of Wolsey) were observed. No projections were found from area 7 to areas SI and SII.

Animals↗
PubMed1988

[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.

Animals↗
PubMed1988

[Cortico-cortical connections in the parietal area of the cerebral cortex].

Layer-by-layer arrangement of the commissural and associative fibers has been studied in the cat parietal cortex. The commissural fibers are distributed in all the layers of the parietal cortex in the contralateral hemisphere, except the superficial part of the I layer. These fibers mainly terminate in the III, IV layers of the contralateral parietal cortex, though their termination in other layers is not excluded. The associative fibers of the parietal cortex are distributed in all the layers of the sensomotor area, except the superficial part of the I layer. They mainly terminate in the III, IV, V layers of the primary somatosensory and in the III, V layers of the motor cortex.

Animals↗
PubMed1987

[Neuronal and neurochemical mechanisms of hypothalamic inhibition of the pain reflex].

Effect of high-frequency stimulation of medial and lateral areas of the posterior, tuberal and anterior hypothalamus as well as of the periaqueductal gray (PAG) on jaw-opening reflex elicited with tooth-pulp stimulation, was studied in anesthetized cats. The m. digastricus EMG response was suppressed with stimulation of all hypothalamic structures. The threshold of the inhibitory effect was lower in the PAG stimulation. Hypothalamic stimulation-produced antinociception was reversed by the specific opiate antagonist naloxone, effect of PAG stimulation being less sensitive to naloxone. After bilateral lesion of PAG the antinociceptive effect of the hypothalamus was only slightly reduced. Complete inhibition of the EMG nociceptive response, similar to the effect of hypothalamus and PAG stimulation was induced with administration of an opiate agonist phenaridine.

4-Aminopyridine↗
PubMed1986

[Interhemispheric connections of the parietal area of the cat cerebral cortex].

The interhemispheric connections of the temporal cortical area in the cat cerebrum have been investigated after electrolytic coagulation of separate fields with subsequent study of the degenerated fibers course after Nauta--Gygax method. The fields 5 and 7 give origin mainly to homotopic fibers, terminating in symmetrical fields of the contralateral hemisphere. These fields also give origin to a small number of heterotopic commissural fibers, that provide bilateral connection of the fields 5 and 7 and do not get beyond the limits of the temporal cortex. The commissural fibers of the temporal cortex get into the contralateral hemisphere through the corpus callosum. In the latter, the commissural fibers of the field 5 are situated more rostral of the fibers running from the field. 7. This corresponds to topographic arrangement of the fields on the cortical surface.

Animals↗
PubMed1976

[Efferent connections of different hippocampal fields with the septum and diencephalic and midbrain structures (fornical efferent fibers)].

The fornical projection of certain fields of the hippocampus was studied after stereotaxical lesions of them by thin electrodes (not thicker than 100 mu). Degenerated fibres were studied by the method of Nauta--Gygax and Knook in serial sections prepared in sagittal, horizontal and frontal planes. The fornical projection was found to be different for different fields of the hippocampus. The subiculum, fields H1 and H2 send their efferents though the inferior fornix into pre- and postcommissural parts. The fibres running to the precommissural fornix terminate in the medial, lateral, dorsal nuclei of the septum, in the nucleus of the diagonal bundle and in the frontal continuation of the hippocampus. The fibres running to the postcommissural fornix, sending a small number of preterminals to the frontal, non-specific group of nuclei of the thalamus, frontal hypothalamic field and the central grey matter surrounding the Silvius aqueduct, terminate in mamillary bodies (in the medial nucleus and a small number of them-in the lateral nucleus). Fields H3, H4, H5 send their efferent fibres through the inferior fornix only to the precommissural part of the fornix; they terminate in the septo-fimbrial, medial, dorsal, lateral nuclei of the septum, in the nucleus of the diagnoal bundle and in the frontal continuation of the hippocampus of the of the ipsi- and contrataral side. Greater Fields H2, H4, 4K send no efferent conductors to the postcommissural fornix. Fields H3, H4, H5 send no afferent conductors to the post-commissural fornix. The denate fascia has no extrahippocampal projection.

Animals↗