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.     

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.     

Effect of novocaine block of limbic system formations of the brain, hypothalamus and reticular formation on evoked potentials in the ventrobasal thalamic nucleus of the rat

The effect of novocain on evoked potentials (EP) recorded from the ventrobasal complex (VBC) of rats thalamus has been studied during a single pulse stimulation of the contralateral hind paw immobilized with curare. It has been established that significant sinchronized decrease of amplitudes of all the three early components of EP has been observed during the novocain administration in the reticular thalamic nucleus, lateral amygdaloid area and septum. During the blocking of the anterior and posterior hypothalamus the amplitude of the second negative component of EP in VBC decreases, while during the blocking of the dorsal hypothalamus an increase of the amplitudes of all the three early components of EP is mainly observed.     

Effect of local surface cooling of the rat cortex on the impulse activity of neurons assumed to be the sources of corticofugal influences

In an experiment on albino rats with electrodermal stimulation of the forepaw evoked potentials (EP) in the neostriatum (NS), the cortical primary response (PR), and impulse reactions of neurons (mainly of layers V and VI of the cortex) were recorded. The zone of leading-off of the potentials in the cortex was subjected to local surface cooling, which led to an increase in the PR amplitude. This facilitation was accompanied by a change in the time parameters of the impulse reactions of the cortical neurons: the latency and duration increased, and a rhythmic organization of activity appeared or intensified (if it was already present). The increase in the PR amplitude and number of spikes in the response of the cortical neurons to stimulus presentation was far less intensive than the sharp increase in EP amplitude in the NS, and did not correspond to it fully in time. The data suggest that the activating influence of the corticofugal signal on EP in the NS is determined not so much by the intensity of the descending signal as by its temporal organization.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 23, No. 2, pp. 181–189, March–April, 1991.     

Changes in evoked potentials to light in the presence of lesions of the diencephalic and brainstem regions of the human brain

Evoked potentials (EPs) to light were studied in groups of patients with tumours of basal-diencephalic localization (24 patients) and at the brain-stem level (24 patients), in comparison with 11 normal subjects. In the first group, a decrease of amplitude and increase of response duration were found in the frontal cortical areas, with simultaneous reduction of intrahemispheric differences due to decrease of low-frequency components in the EP spectra by amplitude in fronto-central parts, and of alpha- and beta-frequencies in the occipital parts of the hemispheres. EP changes resulting from brain-stem tumors were more expressed than in the case of cerebellar tumors. In patients with foci causing a pronounced irritation of the brain-stem, a decrease in responses amplitude was observed accompanied by an amplitude lowering of delta- and theta-frequencies in EPs-spectra in the frontal, central and temporal leads, with no changes in the occipital leads. The obtained data testify to functional inequivalence and independence of different EP frequency components suggesting that the methods of studying the EP frequency structure are informative and efficient.     

Dynamics of evoked potentials in the auditory zone of the dog cerebral cortex following extirpation of the medial geniculate bodies during formation of goal-directed behavior]

Integrative processes in the auditory cortical zone were studied in three dogs by EEG and EP parameters during the formation of a defensive reaction to clicks (four clicks, two per second) after the extirpation of the medial geniculate bodies. In the operated animals information is transmitted to the cortical end of the auditory analyser by compensatory paths with a larger number of relays. In the auditory cortex EPs are recorded with a longer latency (12 to 16 msec), and the duration of the negative EP component is increased (up to 40 msec). It is split mainly on the ascending front. The cortical end of the analyser participates in the formation of processes of afferent synthesis. In the active period of reflex elaboration the inflow of information increases: the EP amplitude and the duration of its main negative component become greater (up to 45-55 msec), as well as the splits on its fronts. In the course of preparing for a decision, before the achievement of the conditioned reaction, a "double EP" appears, which is due to enhanced reverberation of excitations in the compensatory paths.     

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.     

Characteristics of cortical responses to electrostimulation of the internal geniculate body during formation of a defensive conditioned reflex]

During elaboration of a classical defensive conditioned reflex the dogs exhibited a dependence of the changes in amplitude and configuration of evoked potentials (EP) to electrical stimulation of the medial geniculate body (MGB), a conditioned stimulus, on the nature of effector manifestation of the conditioned reflex: the late components were the most depressed at multiple phasic reactions and not infrequently increased and became complicated at single and short motor reactions as well as at their incidental absence. The primary oscillations, while mostly remaining unchanged, were depressed in the case of conditioned reactions attended with a general motor restlessness. A difference has been revealed during conditioning in the EP changes to electrical stimulation of MGB and to an adequate peripheral stimulation. It has been assumed that EP changes during conditioned activity are determined by the relationship between the levels of tonic and phasic cortical activation.     

Angiotensin II, bombesin and naloxone in tooth pulp and cutaneous nociceptive mechanisms in rabbits

The effects of angiotensin II (A II), bombesin (B) and naloxone (N) on the amplitude of the late component of the evoked potentials of the cortex (EP) were studied by electrocutaneous (ECS) and tooth pulp (ETS) stimulation. An intraventricular (50 ng/kg) or intravenous (5 micrograms/kg) injections decreased the amplitude of the negative-positive component with a 20-40 ms latency (NP20-40) EP to ETS, but not to ECS. Saralasin (A II antagonist) injected intraventricularly (130 ng/kg) abolished this effect of A II in response to ETS. N intraventricular injections (30 micrograms/kg) increased the amplitude of NP20-40 EP to ETS, but not to ECS. B (intraventricular injection 20 ng/kg decreased the amplitude of NP20-40 EP to ECS, but not to ETS. This suggests there are the specific mechanisms in analgesia induced by A II and B in the pathways activated by ECS and ETS.     

Effect of beta-phenylethylamine on evoked potentials of the neostriatum of rats]

The effect of intraperitoneal (70 mg/kg) and local (39 ug) administration of beta-phenylethylamine (beta-PEA) on evoked potentials (EP) in the caudate nucleus upon stimulation of substantia nigra zona compacta (SNC) and frontal cortex in rats has been studied. beta-PEA, glutamate and haloperidol were injected into the caudate nucleus by means of a system consisting of a pushpull cannule and an electrode for simultaneous registration of EP. Specificity in the effect of the drugs on EP in response to stimulation of the cortex and substantia nigra was revealed. The intraperitoneal injection of beta-PEA induced, comparatively to the application, more rapid and potent decrease in the amplitude of the component (N2-P2) as a result of the substantia nigra stimulation and slightly influenced the EP amplitude in stimulation of the frontal cortex. It was established using haloperidol that the component (N2-P2) of EP in response to the substantia nigra stimulation is of dopaminergic neuron function in the nigro-neostrital system of the rat brain.     

Spatiotemporal characteristics of evoked potentials in the posterior ventrolateral nucleus of the cat thalamus

Evoked potentials (EPs) in the posterior ventrolateral nucleus (VPL) of the thalamus in response to electrical stimulation of the skin of the contralateral forelimb were studied. It was shown that they are formed by superposition of several electrical dipoles, one of which lies with two poles in VPL while the rest have one pole in VPL and the other in more caudal zones of the somatosensory system. The first phase of the EP in VPL consists of two components with different amplitude—frequency characteristics. The lability of the second component is low and it disappears if the frequency of stimulation rises above 20 Hz. The focus of maximal activity during contralateral stimulation of the skin of the forelimb occupies the same topographical position in VPL during development of the positive and negative phases of the EP. The steepness of rise of the ascending phase and the amplitude of the positive phase of the EP are greatest at the focus of maximal activity; in other regions the lines of equal steepness need not necessarily coincide with the equipotential lines; differences are especially noticeable in the sagittal plane.Institute of the Brain, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 4, No. 4, pp. 439–446, July–August, 1972.     

Reduction of intractable seizures using cerebellar stimulation

Of the 32 patients with active intractable seizures, 27 had spastic cerebral palsy (CP) and 5 had epilepsy (EP), and all underwent chronic cerebellar stimulation (CCS) (amplitude 1-2 microC/cm2/phase, rate 10-180 pps, duration of implantation 0.5-7 years, average 4.5 years). Grand mal seizures occurred in 23 patients (19 CP, 4 EP); with CCS 17 patients stopped, 4 had a reduction, 3 were unchanged. Petit mal occurred in 9 patients (8 CP, 1 EP); with CCS 4 patients ceased seizuring, 3 reduced and 2 were unchanged. Myoclonic seizures were present in 6 patients (5 CP, 1 EP); with CCS 1 patient stopped, 3 had a reduction while 2 patients were unaffected. Severe psychomotor seizuring affected 2 EP patients, 1 had a marked behavioral improvement and finally stopped seizuring for the past 9 months. Overall, CCS stopped 18 (57%) of the patients seizuring, reduced a further 9 (28%), with no effect in 5 patients (15%).     

Evoked frequency stabilization in the electrical activity of the cat brain

In this study, our previous results on the important relation between EEG and EPs were extended by experiments with chronically implanted and freely moving cats, which had electrodes at the acoustical cortex, inferior colliculus and reticular formation. During the experiments the frequency stabilization upon sound stimulation was shown in the frequency domain by comparison of the pre-stimulus power spectra and post-stimulus amplitude frequency characteristics. Comparative frequency domain analysis of about 75 EEG-EPograms (sample of spontaneous activities just prior to stimulation and single evoked potentials following the stimulation), which were recorded from all the brain nuclei mentioned above and from each of the 11 cats, was performed as follows: 1) Power spectra of the EEG-records prior to stimulus were evaluated. 2) Instantaneous frequency characteristics of single EPs were obtained by the Fourier transform. 3) Distribution of the amplitude maxima of the EP-frequency characteristics and the distribution of the EEG-spectral peaks were compared by plotting two types of histograms containing relevant spectral peaks before and after the stimulation. In a frequency range between 1–1000 Hz, the frequency distribution of the EP records from RF and IC were accumulated in narrow discrete frequency channels, whereas, the distribution of the spectral peaks of the EEG depicted frequency spread in broad channels. The frequency stabilization of the EP records from GEA, in the alpha frequency range, was also observed. This effect was described by a factor which we called as the Frequency Stabilization Factor. The results presented in this study showed that the frequency stabilization of the brain's electrical activity induced by sensory stimulation displayed a fluctuation leading to frequency stabilization factors between 0.95 and 5.00. The frequency stabilization and relevant power enhancement upon stimulation strongly support our contention that evoked potential results from the frequency stabilization of the spontaneous activity, triggered by stimulation.Supported by Grant No. TAG-345 of the Scientific and Technical Research Council of Turkey     

Evoked potentials in the rat neostriatum during local cooling of the cortex in the zone of primary response to the applied stimulus

The effect of local cooling of the surface of the somatosensory cortex was studied while recording primary response (PR) in the center of a cooled area and evoked potentials (EP) in the striatum to the forepaw stimulation. The cooling which served to arise the amplitude of the PR, served also to arise the amplitude of the EP in the striatum. EP to the stimulus, the sensory representation of which in the cortex was cooled, were facilitated only. Facilitation of the striatal EP was more intense than facilitation of the cortical PR in the cooled area. The level of facilitation of the EP was the same in the region of the striatum which receives corticofugal fibers from the cooled area of the cortex and in other regions of the striatum, receiving the corticofugal fibers from other parts of the cortex. The data show a possibility for the interactions in the striatum of the corticofugal signals from different cortical areas with each other and with the ascending afferent signals.     

Estimation of the interaction strength in the rabbit sensomotor cortex neurons before and after formation of the defense focus

The strength of interaction between neurons in the sensorimotor cortex of rabbits was compared before and after the formation of a hidden excitatory focus (dominant) in this cortical area. In control experiments the interactions between the neurons was significantly stronger in cases when the influence of the neurons with higher spike amplitude on the neurons generating lower-amplitude pulses was assessed. This difference disappeared in the dominant focus.     

Comparative study of the rod and cone contributions to the generation of b-wave ERG and tectal evoked potential in the dark-adapted carp

Amplitudes and peak latencies as functions of wave length and monochromatic light intensity were investigated for b-wave ERG and tectal evoked potentials (EP) in the dark-adapted carp (Cyprinus carpio L). It was found, that independently of light intensity b-wave action spectra had one maximum in the medium wave band, corresponding to rod sensitivity area. For tectal EP, similar action spectra with maximum in the middle-wave were seen at low light intensity only. The b-wave amplitude growth was significant for the whole band of light intensities, and these changes were accompanied with a slight decrease in peak latency (to 50-100 ms). Tectal EP amplitude increased when low-intensity light was changed for medium intensity light and did not considerably increase to brighter light stimuli. However, tectal EP time latency significantly decreased (to 100-200 ms) during light intensity increasing. This differences show that retinal rod system, which in responsible for ERG b-wave in darkness, is not a key factor in the generation of tectal EP.     

The reticular formation differentiates heterotopic stimuli

The role of the reticular formation (RF) in discriminative functions was studied in experiments on anaesthetized cats. In this association, a) the variability of responses in the RF (bipolarly recorded potential gradients - PG) to the same stimuli, and b) the responses of the RF to different (heterotopic) stimuli were recorded. The PG pattern in electrical stimulation of the same source (a nerve, skin) was constant during the time periods studied (several tens of minutes); even when the functional state of the RF was modified with strychnine, the basic characteristics of the responses usually remained intact. The pattern of PG generated by natural stimulation (tapping) was likewise reproduced with exactness at the level of statistical significance. Responses evoked from reciprocally remote receptor areas were manifestly different, at least in one of the depths investigated. The differences in stimulation of topically close areas were small. The results show that the RF, through its reactions, can differentiate heterotopic stimuli.     

Characteristics of evoked potentials and single neuron responses in the cat sensorimotor cortex to sound stimuli with different frequencies.

The characteristics of the averaged evoked potentials (AEP) (experiments with awake non-paralysed animals), of the evoked potentials (EP) and of the responses of single sensorimotor cortical neurons (acute experiments) of cats to tone-bursts with frequencies within 0.1-6.0 kHz were studied. Response selectivity to the tone-burst frequencies which are energetically pronounced in some biologically significant sounds for the cat was observed. The averaged curve of the dependence of the amplitude of AEP in the somatosensory cortical region (S1) on the tone-burst frequency has reliable maximum values at the frequencies of 0.8, 1.6 and 2.0-3.0 kHz. Most pronounced changes in the heart rhythm were observed within the tone-burst frequency ranges in which the AEP of the highest amplitudes were recorded. The amplitude of the AEP was found to increase during the conditioned reflex elaboration. The curve of the dependence of the probability of the EP occurrence on the frequency at equal sound pressure levels had maximum values at the frequencies of 1.6 and 3.2 kHz. The highest amplitude values of EP were found at frequencies of 0.8, 1.6 and 3.2 kHz. More than half of the recorded neurons revealed the lowest values of the response thresholds and the maximum values of the occurrence probability under suprathreshold stimulation at frequencies close to 0.8, 1.6, and 3.2 kHz. It is supposed that the above mentioned feature of the input frequency organization in sensorimotor cortex is connected with the selectivity as to the biological significance of acoustic stimuli.     

GABA metabolism and the formation of a sensorimotor cortex evoked potential in the presence of excess zinc ions

Changes in GABA content, the enzymatic activity of its metabolism and the formation of sensorimotor cortical evoked potential (EP) were studied following long-term ZnCl2 administration. It has been established that a single ZnCl2 injection at a dose of 0.1 and 1 mg/kg was accompanied by an increase in the amplitude of sensorimotor cortical EP, though GABA accumulation in this brain structure was observed. This might account for the prolongation of the period of the potential appearance. Long-term (for 7, 14, 21 days) ZnCl2 administration at a dose of 0.1 mg/kg produced a sharp depression in the potential appearance and an increase in GABA content by 50% with the enhancement of glutamate decarboxylase activity and the attenuation of GABA-transaminase activity.     

The heterogeneity of the excitatory synaptic inputs in the spinal motor neurons of the frog Rana ridibunda

The synaptic responses induced in motoneurones by the stimulations of the dorsal root (DR), single afferent fibres and reticular formation (RF) were intracellularly recorded in the isolated frog spinal cord. It was shown that argiopine (the selective blocker of glutamate receptors of non-NMDA type) in concentrations ranging from 3.10(-7) to 1.10(-5) M effectively suppressed the di- and polysynaptic, but not the monosynaptic components of EPSP's induced by DR stimulation. The initial reaction to argiopine consisted of the increase of this monosynaptic component of EPSP. In the same concentrations range, argiopine reduced both mono- and polysynaptic EPSP, evoked by RF stimulation. 2-amino-phosphonovaleric acid (1.10(-4) M) did not affect, whereas the kinurenate (1--2.10(-3) M) completely blocked the amplitude of all kinds of synaptic responses. The various effects of argiopine on the responses induced by microstimulation of presynaptic nerve terminals were observed. The data obtained speak in favour of heterogeneity of monosynaptic excitatory inputs in the motoneurones of frog spinal cord. Being the glutamatergic by nature, the inputs differ in the properties of postsynaptic receptors. All of these receptors concerning to non NMDA-type can be divided to argiopine-sensitive and argiopine-resistant. The first seem to be involved in the monosynaptic connections of RF and the second--in those of primary afferents with motoneurones.