Studies on projections of somatic afferentation in the neocortex of the hedgehog Erinaceus europaeus]

Cortical projections of the somatic system in the hedgehog cortex were studied by means of the evoked potential (EP) technique. The EPs were shown to arise at a large area of the lateral cortex, the area in question being enlarged under chloralose anaesthesia. In the focus of projection of corresponding modalities the EPs posessed the least latency. Functional differences in the EP generation system both in the focus of projection and outside it are discussed. The wide EPs spreading in the lateral cortex as well as the presence of relatively differentiated projections is supposed to depend on the afferent volley dispersion to the polysynaptic pathways at the thalamic level. Considerable overlapping of sensory projection zones in the cortex is conditioned by the latter and indicates low degree of the somatic analyser organization.     

Organization of the Viscerosomatic Afferent Projections to Fields 24 and 25 of the Cingulate Gyrus of the Cat Brain Cortex

We studied evoked potentials (EP) and responses of single neurons in fields 24 and 25 of the cingulate gyrus of the cat brain cortex. The responses were elicited by stimulations of a parasympathetic, a sympathetic, and a somatic nerve (the pelvic, splanchnic, and sciatic nerves). The configuration and amplitude/temporal characteristics of both EP and neuronal responses showed that the organization of the visceral and somatic afferent inputs to the cortical fields under study is to a great extent similar. Localization of the foci of maximum activity for EP within field 24 and their overlapping, the higher responsiveness of the neurons of this field to afferent volleys as compared with that in field 25, the dominance of short-latency neuronal responses in field 24, and the presence of polysensory neurons with modally specific opposite responses in this field allow us to conclude that field 24 (compared with field 25) plays a more significant role in the perception and analysis of viscerosomatic afferent information. Taking into account earlier published data that the zones of concentration of the efferent neurons (forming a descending limbico-sympathetic discharge in the L2-L3 white connective branches and a limbico-parasympathetic discharge in the pelvic nerve) are localized within field 25 and overlap each other, we discuss the functional roles of fields 24 and 25 of the cingulate gyrus in viscerosensory and visceromotor control.     

Dynamics of changes in somatosensory input to the motor cortex following lesion of somatosensory cortical areas in dogs

The pattern of change produced in somatosensory evoked potential (EP) in the forelimb projection area within the motor cortex (MI) following lesion of the projection area of the same limb in the somatosensory cortex (SI) or in parietal cortex area 5 was investigated during chronic experiments on waking dogs. Amplitude of the initial positive — negative wave of EP declined to 28–63% of preoperational level in all cases. No significant recovery of EP was noted for three weeks. Thus, a correlation between change in EP and spontaneous recuperation of the precision motor response occurring within two weeks after lesion of the SI did not exist. Nor was EP reinstated in the MI after ablation of area 5, despite complete but gradual reinstatement of EP (after an initial decline to 53%) in the nearby SI region. This protracted depression of EP seems to have been associated with breakdown of somatotopic sensory input from the SI or from area 5 to the MI, since EP in the motor cortex of the intact hemisphere and the hindlimb projection area within the MI on the lesioned side either remained unchanged or recovered within a week or two.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 61–68, January–February, 1990.     

Effect of positive and negative emotional states on the electrical activity of the auditory cortex in rabbit ontogeny

It has been shown that in all age groups of animals, self-stimulation of the hypothalamus is accompanied with the decrease in the latent period and the increase in the amplitude of the evoked potential (EP) in the auditory cortex. During negative stimulation, the increase in temporal parameters of the response takes place together with the decrease in the amplitude of the EP and the onset of secondary waves. Significant age changes were revealed in the recovery of the initial pattern of the EP after cessation of stimulation of emotiogenic zones. The recovery of the EP after stimulation of the "reward" zone in younger rabbits occurs 4 times faster than in adult animals, whereas in the former the recovery period of the EP after stimulation of the "punishment" zone is significantly longer.     

The influence of recognition of a visual stimulus on evoked potentials of the projection and non-projection areas of the cerebral cortex]

Evoked potentials (EP) were recorded in the projection and non-projection areas of the cerebral cortex in juveniles in response to exposures of structured visual stimuli with subthreshold and supraliminal durations. The data obtained have shown that recognition of the presented stimulus is attended with intensification of the EP late complex. This effect is most pronouned in the central and frontal parts of the cortex. The Nv component with a 240 to 300 msec latency has a more regular connection with recognition as compared with other components.     

猫皮层体感Ⅱ区内脏伤害感受神经元的电生理特性及形态特征

应用胞内记录和标记技术,观察了猫皮质第Ⅱ感觉区内脏大神经代表区的神经元对电刺激内脏大神经反应诱发反应及形态特征。结果表明,在２５１个记录单位中,有１０９个为内脏伤害性感受神经元,其诱发反应分为兴奋性、抑制性及混合性三类。在形式上ＩＳＰＳ及ＥＰＳＰ－ＩＰＳＰ序列反应较多。对其中２１个神经元用神经生物素进行细胞内电泳标记,显示细胞的形态特点是胞体较小,分布于皮质Ⅱ、Ⅲ、Ⅴ层,其中兴奋性和神经元形态多为     

Demonstration of interactions between visual and splanchnic afferences at the level of the cerebral cortex in cats]

In the chloralose-anesthetized cats, evoked potentials (E.P) were recorded from cerebral cortex with the use of 1) macroelectrodes in two overlapping zones between splanchnic and visual areas : Medial Lateral and Anterior Suprasylvian (S II) gyri ; 2) microelectrodes in Medial Lateral gyrus. Our results show : 1) a strong increase of the primary visual E.P. in Medial Laternal gyrus by splanchnic stimulus ; 2) a strong inhibition of the primary splanchnic E.P. in S II by visual stimulus ; 3) an inhibition of some cortical neurons in Medial Lateral gyrus by splanchnic stimulus ; 4) an inhibition of associative visual E.P. in S II by splanchnic stimulus, and of associative splanchnic E.P. in Medial Lateral gyrus by visual stimulus. In the other hand splanchnic and visual E.P. were recorded from N. reticularis and Corpus Geniculatum Mediale with the use of concentric electrode. Some hypothesis concerning interrelations mechanisms are discussed.     

Habituation of direct cortical responses in cats

Gradual diminution of direct responses of various cortical areas was studied in acute experiments on cats under barbiturate anesthesia. During repetitive stimulation of the surface of cortical association areas these responses underwent all changes characteristic of the habituation phenomenon. Direct cortical responses in primary projection areas were distinguished by great stability, and habituation was absent in this case. After neuronal isolation of an island of projection cortex, habituation of responses began to develop there just as in the cortical association areas. The possible causes of differences between changes in direct cortical responses in different areas are discussed. It is suggested that projection areas receive strong activating influences from deep brain structures, which exert a sensitizing effect on the direct responses.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 13, No. 3, pp. 241–246, May–June, 1981.     

Analysis of hippocampal sensory EP-changes in dependence on activation level]

Photically evoked potentials were recorded from the visual cortex (VC) as well as CA 1/2- and CA 4/Fascia dentata-region of the dorsal hippocampus in alert resting rabbits. Analysing the whole time-course of the individual hippocampal EP attention was focused on components corresponding in time to the late negative complex of the cortical EP. Enhancement of such components was seen following habituation to repeated flashes. These changes occurred concerning components in the CA 4/FD-record with shorter latency. The duration and peak latency, however, was longer in CA 4/FD than in the other records. During stimulation of the medial septal nucleus a diminution of late EP-components was seen in the visual cortex and less pronounced in the hippocampus. The time-course of the changes was almost the same in VC and CA 4/FD, whereas in CA 1/2 later components were affected. RF-stimulation caused very similar changes, while those in hippocampal EP's were extended up to later components. Whereas the time range of changes in the hippocampal EP's to all influences under investigation was almost the same, in the VC by RF-stimulation in contrast to habituation components with shorter latencies were affected. In this way it is supposed that for the VC different processes are affected by the three influences, while this could not be established for the hippocampus.     

Electrophysiological study of connections between the entorhinal cortex and the neocortex

In acute experiments in rabbits immobilized by d-tubocurarine, stimulation of the entorhinal area with rectangular electric impulses led to the appearance of evoked potentials (EP) with a latent period of 6–12 msec in the occipital, temporal, parietal, and cingular areas of the neocortex. The amplitude of the positive response component was 500 µV, and its duration 25–50 msec. The negative component was not always discernible. When rhythmic stimulation was used, these EPs followed stimulation frequencies not exceeding 20 per sec. Stimulation of the medial parts of the entorhinal area with a frequency of one to three per sec was accompanied by recruitment of the EP in the occipital and temporal neocortex areas. Nembutal depressed the amplitude of the neocortex EP appearing in response to stimulation of the entorhinal cortex. With the aid of double stimulation it could be established that, after conditioning stimulation of the entorhinal area, the positive component of the primary response (PR) evoked by stimulation of the contralateral sciatic nerve in the projection zone of the somatosensory cortex is strengthened during the first 50 msec, and subsequently after 80–120 msec. In these cases, the negative component was depressed. These findings are discussed with a view to the influence of limbic structures on the neocortex.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 2, No. 1, pp. 73–78, January–February, 1970.     

Effect of motor deprivation in early ontogeny on evoked potentials of the sensomotor and visual cortex in the rat

The influence of long-term (3 months) locomotor deprivation of rats in a month age, on the evoked potentials (EP) of the sensorimotor and the visual cortex was studied in conditions of presentation of single and paired stimuli. Changes were revealed in both cortical zones. An increase of peak latency of the initial positive EP phase in the sensorimotor cortex, and prolongation of the process of changes in excitability of neural elements, elicited by conditioning stimulus, was revealed both in the sensorimotor and the visual areas. The effect of deprivation on the dynamics of changes in neuronal systems excitability was greater in the visual evoked responses.     

Mechanisms of transmission of excitation grnerated in the orbito-frontal cortex]

Experiments carried out on cats showed that interhemispheric generalization of strychnine spasmodic potentials from the orbito-frontal cortex were mainly brought about by the callosal pathway. In contrast to other projection and association zones of the cortex only the frontal portion of the corpus callosum (the rostrum) and not the whole corpus took part in transmitting strychnine commissures. The results of investigations carried out were consistent with the general conception of the principle of the determining dispatch station (DDS) in the nervous system integration activity. These results reveal that the appearance of the DDS induces secondary excitation foci which fully reproduce tha work regimen of the DDS. Switching of such "mirror" foci representing "the destination stations" from the DDS influence led to the elimination of the activity induced in them.     

An analysis of interhemispheric interrelationships in the visual cortex of cats based on the law of contrast perception of light]

The dependence of EP amplitude on the intensity of photic stimuli before and after section of the callosal body may be fully defined by the equation of the contrast law of light perception. Analysis of the nature of interhemispheric relationships by means of contrast law has shown that both reciprocal depressing and reciprocal facilitating interhemispheric relationships may exist in the primary visual cortical projection zone, and reciprocal facilitating interhemispheric influences in the secondary visual projection zone. Similarity of interhemispheric relationships has been recorded in the primary visual cortex in cats and in the secondary one, in rats, as well as in the socondary visual cortical zone in cats, and in the primary, in rats. Interhemispheric reciprocal influences in the whole range of stimuli intensities are distributed more uniformly in cats than in rats. Cats may perceive a wider range of intensity of photic stimuli than rats. In cats as in rats, the effectiveness of processing of the photic stimuli contrast is greater in the secondary visual cortical projection zone than in the primary one.     

Features of changes in bioelectric reactions of the cerebral cortex in rats with deafferentation pain syndrome]

In rats with pain syndrome after sciatic nerve section the authors studied spontaneous and evoked bioelectric activity in sensomotor cerebral cortex of both hemispheres. Electrocorticogram showed the presence of hyper-synchronic discharges and paroxysmal peak-wave (700-800 mV) activity in contralateral hemisphere. While stimulating the injured limb the threshold of evoked potentials (EP) was observed to decrease, its amplitude to increase and focus maximum EP activity to extend.     

Dynamics of evoked potentials in cortical projection structures during a retarded instrumental defense reflex in dogs]

Evoked potentials (EP) in the somatosensory and auditory cortical areas were studied in four dogs against the background of a retarded defensive instrumental conditioned reflex to clicks. Four phases of the reflex were singled out by the changes in the structure of EP late components (LC) in the two projection zones. The most complex LC changes in the form of intensified negative components and the appearance of additional negative LC are recorded in response to the first click of the series and to the one followed by the conditioned motor reaction (CMR). Against the background of CMR delay, the EPs increased, while during the CMR, they decreased, owing to the diminished negative components, while the positive components were preserved and sometimes intensified. An assumption has been made that cortical projection structures of paired stimuli function in one and the same regime.     

Reticular activation by splanchnic afferents: its influence on visual projections at the level of the cerebral cortex in cats]

In an previous work, we have shown a strong increase of visual evoked potentials of the medial lateral gyrus by splanchnic stimulation. This present study demonstrates that this effect is due to the activation of the substantia reticularis. Actually, we observed: 1) an increase of the reticular visual potential by splanchnic stimulus in convergent zone; 2) an increase of the visual evoked potential in the primary cortical area by stimulation of this reticular formation. These results show the existence of a functional pathway including the splanchnic nerve, the reticular formation and the visual cortex.     

Modulation of the neuronal activity and evoked potentials of the cerebral cortex by stimulation of the dorsal hippocampus]

In experiments on alert rabbits high frequency stimulation of the CA1 field of the dorsal hippocampus reduced the peak latency of the main negative component of the evoked potential (EP) to a light flash in the sensorimotor and occipital tests areas of the cerebral cortex. A single stimulation of the same part of the hippocampus resulted in a gradually developing facilitation of secondary negativity of the EP 5th component, predominantly in the sensorimotor cortex. Investigation of neuronal responses in the same cortical areas to a stimulation of the CA1 field with different parameters has shown that the effects of EP modulation are due to dynamic reorganizations of cortical neuronal activity.     

Effects of clentiazem (TA-3090) and nifedipine on basal circulating catecholamine levels and on stimulation-evoked adrenal catecholamine secretion in anesthetized dogs.

The effects of TA-3090 (clentiazem) and nifedipine on basal sympathoadrenal activity and on the adrenal medullary response during splanchnic nerve stimulation were studied in dogs anesthetized with sodium pentobarbital. Plasma concentrations of epinephrine and norepinephrine were measured in aortic and adrenal venous blood before and after acute administration of the drugs, as well as during left splanchnic nerve stimulation before and after administration of drugs. Following intravenous injections, TA-3090 (30, 100, and 300 micrograms/kg) did not affect basal circulating catecholamine levels, whereas nifedipine (10, 30, and 100 micrograms/kg) markedly increased aortic epinephrine and norepinephrine concentrations in a dose-dependent manner in correlation with progressive decreases in mean arterial pressure. The changes in aortic epinephrine and norepinephrine concentrations were inversely related to those in mean arterial pressure (r = 0.603, p < 0.01; r = 0.536, p < 0.01; respectively). In response to direct splanchnic nerve stimulation (2 Hz, 2 ms, 1 min, 12 V), adrenal venous epinephrine and norepinephrine concentrations significantly increased, with a high degree of reproducibility. The catecholamine responses to splanchnic nerve stimulation were not affected by either TA-3090 or nifedipine at any dose tested. The present results suggest that the increases in circulating catecholamine levels following nifedipine administration are due to baroreflex activation secondary to the drug-induced hypotension. The study indicates that both TA-3090 and nifedipine did not significantly affect L-type Ca2+ channels related to catecholamine release in the adrenal medulla under the present experimental conditions.     

Analysis of auditory information in the brain of the cetacean

The cetacean brain specifics involve an exceptional development of the auditory neural centres. The place of projection sensory areas including the auditory that in the cetacean brain cortex is essentially different from that in other mammals. The EP characteristics indicated presence of several functional divisions in the auditory cortex. Physiological studies of the cetacean auditory centres were mainly performed using the EP technique. Of several types of the EPs, the short-latency auditory EP was most thoroughly studied. In cetacean, it is characterised by exceptionally high temporal resolution with the integration time about 0.3 ms which corresponds to the cut-off frequency 1700 Hz. This much exceeds the temporal resolution of the hearing in terranstrial mammals. The frequency selectivity of hearing in cetacean was measured using a number of variants of the masking technique. The hearing frequency selectivity acuity in cetacean exceeds that of most terraneous mammals (excepting the bats). This acute frequency selectivity provides the differentiation among the finest spectral patterns of auditory signals.     

Functional maturation of the cat visual cortex during prenatal ontogenesis]

Development of the perceiving function of the visual cortex was studied on the foeti of cats in the second stage of antenatal development with intact placental blood circulation. It has been found that functional maturing of the cortical end of the visual analyser starts at the beginning of the second half of antenatal life. At this period EPs to stimulation of the optic nerve are recorded throughout the dorsal cortex of the contralateral hemisphere. At first they appear as slow three-phase (positive-negative-positive) oscillations of a small amplitude. As the foetus develops, the EP amplitude increases, and the EP configuration in the striate zone of the cortex becomes complex. Two weaks before birth, a short-latency negative wave appears against the background of the primary positive oscillation. In the last week of antenatal development of the foeti and in the first few days of the kittens life, EPs are represented in the specific zone of the visual cortex (g. lateralis) as two negative oscillations, and in the so-called associative zone (the middle part of the suprasylvian gyrus) by one long-latency high-amplitude negative oscillation which corresponds by latency to the second negative EP component in the striate cortex.