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At least 1,081 records · Page 60Linked to original sources
PubMed1986

The monoaminergic innervation of primate neocortex.

In brain, the monoamines, dopamine, norepinephrine, and serotonin, are confined to anatomically distinct neuronal systems, each of which furnishes widespread projections to neocortex. In primate, but not in rat, the terminal patterns of each of these systems have a high degree of regional and laminar specificity. These findings suggest that there are different sites of action and possibly different functional roles for each of the monoamines. This type of precise anatomic information is essential to our understanding of the possible involvement of monoamines in human disease states.

Animals↗
PubMedDate not supplied

[Role of cholinergic and adrenergic mechanisms in the action of ketamine and thiopental sodium on the structures of the hippocampal-reticular complex and the neocortex].

Under conditions of free behaviour of rabbits with electrodes implanted into the brain structures it was found that ketamine and sodium thiopental decrease the excitability in the dorsal hippocamp, reticular formation and periaqueductal gray matter of the midbrain. Excitability of the frontal neocortex increases during general anesthesia with ketamine and decreases during thiopental narcosis. Changes in excitability of the studied cerebral structures during general anesthesia can be determined by common N-cholinoblocking and alpha-adrenomimetic properties of ketamine and thiopental at the level of the dorsal hippocamp, cholinoblocking and adrenoblocking properties at the level of the reticular formation and central gray matter. In the frontal cortex ketamine presented properties of an M-cholinomimetic and adrenomimetic agent, sodium thiopental--those of a M-cholinoblocker and beta-adrenoblocker.

Animals↗
PubMed1987

[DNA repair in mammalian nerve cells. I. DNA synthesis in the neocortex of rats induced by gamma irradiation].

A study was made of the DNA synthesis in cerebral cortex of rats, aged 14 and 60 days, after gamma-irradiation in vivo in a dose of 7 Gy, the 3H-thymidine incorporation into DNA being determined.137 Cs-radiation induces additional DNA synthesis in the neocortex tissue and in neurons. In the cortex of 14 day-old rats, the induced DNA synthesis stops 2 hours after irradiation, whereas in the cortex of 60 day-old rats and in neurons of rats of both the age groups DNA synthesis is proceeding for 3-3.5 hours. Specificity of DNA reparation processes in non-dividing cells is discussed.

Aging↗
PubMedDate not supplied

[Conjugation of unit activity in the visual and sensomotor areas of the rabbit neocortex during a conditioned reflex to sound and light].

Conjugation of unit activity in the visual and sensorimotor neocortical areas was studied by means of histograms of cross- and autocorrelation in rabbits with conditioned reflex to light (1st group) and sound (2nd group). Relative number of neurones pairs acting in correlation in the areas remote from each other, in intersignal intervals both before and after stimuli did not differ in the 1st and 2nd groups. At the same time delays in neuronal discharges in one area after the other were different. In the 1st group animals there was a predominance of the number of visual area neurones discharging after sensorimotor with a delay up to 125 ms, in comparison with the number of sensorimotor area neurones discharging after the visual one. In the 2nd group rabbits the number of visual area neurones with such a delay of discharges after sensorimotor was less and, on the contrary, a predominance of sensorimotor area neurones was observed discharging after the visual one. The obtained results allow to suggest that neurones of the visual and sensorimotor neocortex areas form a single functional system in cases when conditioned and unconditioned stimuli are addressed to these areas and when only one of the studied areas is the projection zone for the combined stimuli. Organization of the neurones activity in systems in these two cases is different.

Animals↗
PubMedDate not supplied

[Gamma- and UV-induced DNA synthesis in neurons of the rat neocortex].

Nuclear DNA synthesis in neocortex neurons of neonatal 14- and 60-day rats after in vitro irradiation of isolated sections was estimated by the incorporation of a labeled precursor into DNA. gamma- and UV-radiation increased the rate of DNA synthesis in the cells of animals of all studied age groups. However, the level of the UV-induced synthesis sharply dropped during the postnatal ontogenesis while gamma-radiation-induced synthesis decreased slightly. The peculiarities revealed in the repair DNA synthesis seem to be influenced by the process of postnatal differentiation of a neuron accompanied by the nucleosome length shortening and the decrease in the DNA-polymerase alpha content.

Aging↗
PubMed1986

[Characteristics of the structural organization of the phylogenetically new fields in the human neocortex].

The myeloarchitectonics of the specific human fields 40, 39, 37c, 37b of neocortex and also fields 17 and 19 which are the cortex end of visual analyzer has been studied with the help of neurohistological and quantitative methods. According to the character of the fibrous bundles, their diameter, the quantity of the fibrous in them and the diameter of the fibrous gradual changes from field 17 to field 19 and further to field 39 have been shown. It is an evidence of the succession between phylogenetically older and younger fields of the cortex. The peculiarities of the field quantitative myeloarchitectonics differing in the function and genesis are marked by heterochronous growth of these fields square in the process of evolution.

Adult↗
PubMedDate not supplied

[Correlation of the neuronal impulse activity of different areas of the neocortex in rabbits in the switching of positive and inhibitory conditioned reflexes].

By cross-correlation method conjugation in impulse activity of pairs of simultaneously recorded units in the visual and sensorimotor areas of the neocortex (representations of the conditioned and unconditioned stimuli) was studied during the switching of defensive positive and inhibitory reflexes in rabbits. 30-second fragments of impulse activity were analyzed in intervals before and after three presentations of positive and inhibitory conditioned stimuli (CS). The activity of single pairs of units in the process of stimuli presentation was characterized by instability. Only in 29% of 51 units' pairs the presence or absence of correlation between their discharges was stable. Analysis of activity of 75 pairs of units showed differences in impulse activity in inhibitory and positive tonic reflexes. The number of pairs of correlated units in about 30 s after inhibitory CS decreased (27%) in comparison with the interval before its action (52%). In the inhibitory tonic conditioned reflex, temporal intervals of discharges of one unit correlated with discharges of the second unit undergo changes. The obtained results testify that such parameter as the number of pairs of units with correlated activity in intersignal time interval is very important for the realization of motor reaction to conditioned stimuli.

Animals↗
PubMed1986

[Changes in the functional characteristics of cells of the Clare-Bishop zone after unilateral partial isolation of the cat neocortex].

Evoked single cell activity in the Clare-Bishop area of the cat neocortex was recorded after partial transection of subcortico-cortical connections. Both functional properties of visual, auditory and somatosensory responsive cells and their responses to electrical stimulation of the primary projection area were studied. A week after transection some neurons in the Clare-Bishop area on the operated site recovered their reactions to applied stimuli. Within the first week the sensitivity of the neurons in the intact hemisphere changed; all the recorded cells reacted to light; 80% of the cells had receptive fields that were situated in the contralateral part of the visual area; 62% of the cells reacted to somatosensory stimuli. A week after the operation the number of responsive cells decreased. The peculiar features of the neuronal compensatory reorganization in the Clare-Bishop area and its role in the recovery of visual function is discussed.

Animals↗
PubMed1986

[Interhemispheric asymmetry of the motor representation of the facial musculature in the neocortex of the white mouse].

In anesthetized white mice, the motor representation of the face muscles was determined with the aid of intracortical microstimulation in the frontal neocortex (fields 4, 6, 8). Significant difference was found in the motor responses to low-threshold stimulation in left and right hemispheres. Stimulation of the left hemisphere induced mostly movements of the upper lip and vibrissae, whereas stimulation of symmetrical area in the right hemisphere induced more variable movements. The area of the lip movement was much smaller in the right hemisphere.

Animals↗
PubMed1986

[Responses of neurons of the embryonal neocortex transplanted into the vibrissa projection area of the somatosensory cortex of the adult rat].

Pieces of embryonic rat neocortex were grafted into the barrel-field of adult rats. Extracellular activity of the grafted neurons was registered 3-4 months later. The background neuronal activity in the grafts did not differ neither in pattern, nor in frequency (3.7 +/- 1.4 spikes per s) from that of the normally developing somatosensory cortex. About 57% of the grafted cells responded to deflexion of the contralateral vibrissae by on-effects, 30%-by phasic increase of discharge frequency and 13%-by initial suppression of spontaneous activity.

Action Potentials↗
PubMed1987

Functional subdivisions of the temporal lobe neocortex.

In order to gather evidence on functional subdivisions of the temporal lobe neocortex of the primate, the activity of more than 2600 single neurons was recorded in 10 myelo- and cytoarchitecturally defined subdivisions of the cortex in the superior temporal sulcus (STS) and inferior temporal gyrus of the anterior part of the temporal lobe of 5 hemispheres of 3 macaque monkeys. First, convergence of different modalities into each area was investigated. Areas TS and TAa, in the upper part of this region, were found to receive visual as well as auditory inputs. Areas TPO, PGa, and IPa, in the depths of the STS, received visual, auditory, and somatosensory inputs. Areas TEa, TEm, TE3, TE2, and TE1, which extend from the ventral bank of the STS through the inferior temporal gyrus, were primarily unimodal visual areas. Second, of the cells with visual responses, it was found that some neurons in areas TS-IPa could be activated only by moving visual stimuli, whereas the great majority of neurons in areas TEa-TE1 could be activated by stationary visual stimuli. Third, it was found that there were few sharply discriminating visual neurons in areas TS and TAa; of the sharply discriminating visual neurons in other areas, however, neurons that responded primarily to faces were found predominantly in areas TPO, TEa, and TEm (in which they represented 20% of the neurons with visual responses); neurons that were tuned to relatively simple visual stimuli such as sine-wave gratings, color, or simple shapes were relatively common in areas TEa, TEm, and TE3; and neurons that responded only to complex visual stimuli were common in areas IPa, TEa, TEm, and TE3. These findings show inter alia that areas TPO, PGa, and IPa are multimodal, that the inferior temporal gyrus areas are primarily unimodal, that there are areas in the cortex in the anterior and dorsal part of the STS that are specialized for the analysis of moving visual stimuli, that neurons responsive primarily to faces are found predominantly in areas TPO, TEa, and TEm, and that architectural subdivisions of the temporal lobe cortex are related to neuronal response properties.

Action Potentials↗
PubMed1985

[Ultrastructural characteristics of the neocortex during rehabilitation from the sequelae of long-term protein-energy deficiency].

Electron microscopy of mouse neocortex was carried out during rehabilitation following long-term protein-caloric deficiency. Food rehabilitation led to partial recovery of brain ultrastructure, however, a high neuronal level of secondary lysosoms and lipofuscin bodies was preserved, with the changes in the spine apparatus and synaptic contacts persisting in neuropile. Carnitine addition to food during rehabilitation increased the number of free ribosomes in cortical neurons. A substantial development of granular endoplasmic reticulum was observed. A greater number of spine apparatus cisterns was detected, however, like in conventional rehabilitation, the width of synaptic clefts and postsynaptic densities remained narrower than in control mice.

Animals↗
PubMed1985

[Long-term reorganization of the neuronal activity in field 7 of the neocortex in the cat after unilateral section of the visual radiation].

Changes in functional characteristics of area 7 cells were studied in cats under semichronic experimental conditions. The experiments were done in various periods of time after unilateral dissection of visual subcortic-cortical fibres. Neuronal responses to visual, auditory, somatic stimuli and electrical stimulation of primary cortical areas were studied in intact and impaired hemispheres. Reappearing of neuronal sensitivity to stimuli of various sensory modalities was found in the partially isolated neocortex. Both the number of cells with local visual receptive fields and averaged receptive field size of the cells increased slowly after the operation. Some suggestions about the nature of plastic changes developing in neuronal nets of the parietal cortex after impairment of subcortico-cortical connections are made.

Animals↗
PubMed1985

[Background and evoked activity of septal and hippocampal neurons transplanted into the neocortex of the rat].

Embryonic tissue of the septum and hippocampus was transplanted into a cavity made in parietal neocortex of adult rats. Extracellular recording 4-6 months after grafting revealed units with background spike activity in the grafted tissue. The activity (mean rate 3.6 +/- 0.4 spikes per s) had a random pattern without pathological features. About 90% of the graft cells responded to electrical stimulation of neighbouring cortical tissue with latencies 5-43 ms. The optimal frequencies for driving spike discharges were 5-10 Hz. Postactivatory suppression was observed in most units. The same proportion of the graft cells responded to tactile stimulation of the host animal. Phasic reactions of on-off type with latencies of 50-600 ms were observed. The normalization of the activity in intrabrain grafts as compared to intraocular ones and functional integration of graft units with the host brain are discussed.

Animals↗
PubMed1985

[Structure of the background neuronal activity in thin slices of guinea pig neocortex].

Background neuronal discharges were recorded extracellularly in guinea-pig cerebral cortex slices maintained in vitro. Six types of activity were classified: 1--regular single discharges (38.5%), 2--irregular spikes (6.5%), 3--bursts (6.5%), 4--burst-single discharge (mixed) activity (26.5%), 5--group discharges (2.5%), 6--multineuronal volleys (18.5%). Characteristic distributions of interspike intervals and autocorrelograms corresponded to each of these types of activity. Regular pacemaker-type discharges were most peculiar under conditions of small volumes of the grey matter and lack of afferentation. Such regular activity was never observed in normal or isolated neocortex.

Action Potentials↗
PubMedDate not supplied

[Correlation of neuronal reactions of different regions of the neocortex of the rabbit to conditioned positive and inhibitory stimuli].

The activity of neurones of the visual and sensorimotor areas of the neocortex was simultaneously recorded in rabbits under the action of conditioned, inhibitory stimuli (CS, IS) and at simultaneous presentation of CS and the unconditioned stimulus (US) after trans-switching of the positive and inhibitory conditioned reflexes. Mean time of conjugated reactions of simultaneously recorded pairs of neurons is similar under the action of CS, combined action of CS and US and under IS. During the IS action as compared with CS, the phasic activity of some neurones in different areas increased, and due to this the similarity of reactions also increased; in other pairs of neurones the reactions weakened and the responses similarity decreased. The frequency of the appearance of intervals of the conjugated excitation after CS corresponds to 4.3 Hz; under combined action of CS and US it increases up to 5.9 Hz, and after IS--it decreases to 3.6 Hz. The order of coming into conjugated action of different pairs of neurones changes depending on the signal significance of the stimuli.

Animals↗
PubMed1985

[Effect of local cooling of the neocortex on motor responses evoked by intracortical microstimulation in the rabbit].

Effects of local cooling of the neocortical zone around stimulating microelectrode upon thresholds of initiation of vibrissal motor responses to intracortical microstimulation were studied in alert rabbits. The thresholds increased from 10-50 mua to over 200 microA during the cooling of the deep cortical layers to 20 degrees C - the level of blocking the intracortical synaptic transmission within stimulated zone. A transient decrease of the thresholds of vibrissal responses initiation occurred in slow cooling (1 degree C per 1 min) within the temperature range from 30 degrees C to 25 degrees C on the cortical surface. The neuronal excitation evoked by means of low-threshold repetitive microstimulation seems to be due mainly to indirect transsynaptic ways. The same group of vibrissae, however, respond to stimulation currents about 100 microA as to low-threshold trains of stimuli, only the intensity of motor responses being enhanced. Thus, no involvement of long transcortical axons into excitation of cortical zone occurs with ordinary microstimulation which allows the mapping of motor representations in the neocortex without side-effects.

Animals↗
PubMedDate not supplied

[Analysis of changes in the electrical activity of the neocortex in dogs during the formation of the stereotype of food-procuring conditioned reflexes in them].

A system of food-procuring conditioned reflexes (dynamic stereotype after I.P. Pavlov) was elaborated in dogs. In the interstimuli periods, 0.6 to 0.8 sec. prior the action of the conditioned stimulus, they exhibited a "state of expectancy" characterized by an increase of frequency (up to 80 per sec.) of potential oscillations of a small amplitude (20 to 30 mcv) and their pronounced sychroneity, predominantly in the anterior parts of the neocortex. The conditioned signal acting against such background produced specific reactions in the form of a limited number of bursts (3 to 4 in 0.5 sec.) of highfrequency (up to 100 per sec.) synchronized activity (HSA) of considerable amplitude (50 to 60 mcv) which always preceded conditioned reactions, being in certain temporal relations with them. A correlation-spectral analysis has shown that in the HSA period, electrical activity became considerably more regular; in the intensity spectra the extreme frequencies of the analyzed band (5 to 7 c/s and 90 to 100 c/s) became prominent, and in most cases high values of the coherence function were due to them. HSA reactions are regarded as a major link in the trigger mechanism of conditioned food-procuring reactions.

Animals↗