Shifts in spatial synchronization of rabbit cortical potentials evoked by applying acetylcholine and amizil to the visual area

Acetylcholine solution application to the visual cortex of walking unrestrained rabbit led approximately in 5 minutes to a certain increase of the spatial synchronization of the cortical potentials at the small conditions, the the cortex, 24 EEG channels being used. Under the same conditions, the application of muscarinic antagonist amizil had an opposite more distinct effect. Endogenous cholinergic input increasing the spatial synchronization is supposed to play an important role in the formation of the spatiotemporal cortical potentials' organization necessary for the occurrence of complex behavioural acts.     

The effect of low frequency peripheral stimulation on the tail-flick reflex and evoked cortical potentials in the rabbit

The effects of low frequency peripheral electrical stimulation of innocuous intensity (LES) on the tail-flick latency and the amplitude of the late component of the cortical potentials evoked by single electrical stimuli (20-40 ms latency) were studied in 59 awake and restrained rabbits. Increase of the tail-flick latency and profound decrease of the amplitude of the late positive component of evoked cortical potentials was observed in 50 animals. Five animals of this group and five animals from a group of 9, resistant to electrostimulation, were tested to the analgesic effects of morphine using the same criteria. Positive effects were found in the former but not in the latter group. Naloxone (0.1 mg/kg) profoundly decreased the effects of LES which suggests that an opioid mechanism is involved in the action of conditioning electrostimulation. Pretreatment of the animals with serotonin depletor p-CPA resulted in partial blockade of the effects of LES. The blockade was removed by administration of serotonin precursor 5-HTP. This is in agreement with the hypothesis that the opioid effects are partially exerted through serotoninergic descending pathways.     

Effect of electric stimulation of non-specific and specific thalamic nuclei on the spatial synchronization of cortical potentials in the rabbit

The effect of low-frequency (1-10 Hz) electrical stimulation of nonspecific n. centralis lateralis and n. centrum medianum and specific thalamic (LGB) nuclei on spatial synchronization of biopotentials of neocortical areas and on the process of learning was studied on rabbits. Electrical stimulation of the non-specific nuclei raised the level of correlation of the cortical potentials, while the LGB stimulation, on the contrary, weakened the spatial synchronization between the potentials of the visual and sensorimotor neocortical areas. On the basis of the obtained data a conclusion is made that stimulation of the non-specific thalamus contributes to a more successful formation of defensive conditioned reflex to light unlike LGB stimulation. It is suggested that a certain specificity of the studied subcortical formations in organization of spatial synchronization of the brain biopotentials and in the process of learning is due to morpho-functional peculiarities of these structures.     

The effect of scopolamine on the spatial organization of rat cortical potentials

The influence of scopolamine (1 mg/kg, i.p.) on the spatial organization of the neocortical electrical activity was studied in rats. A decrease in the spectral power and coherence of brain potentials in the range of the dominant theta-rhythm peak (6.00-7.25 Hz) and their increase in the adjacent low-frequency band were observed. Both indices were decreased in the wide beta band (19.00-30.00 Hz). The described changes took place over the whole areas of the right hemisphere and parieto-temporal region of the left hemisphere. The obtained results are discussed with respect to the role of the cholinergic brain system in the higher nervous activity.     

Effect of interruption of descending cortical connections on unit responses to extracellular polarization in the lateral geniculate body

Acute experiments on cats showed that unilateral division of projection connections from the cerebral cortex gives rise to definite changes in the effects of extracellular polarization of lateral geniculate neurons: in 40% of cells the regular firing pattern is disturbed in the initial period of action of anodal polarization, the number of cells with after-responses and prolonged changes in spontaneous firing pattern is significantly reduced, and the number of neurons capable of modifying their type of activity under the influence of an incoming polarizing current is also reduced. After interruption of the descending cortical connections the functional characteristics of the lateral geniculate neurons are altered, with a resulting narrowing of the range of their physiological responses to the polarizing current. These facts suggest that the most complex processes of tonic regulation of unit activity in the lateral geniculate bodies require the active participation of the cerebral cortex.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 4, No. 6, pp. 629–635, November-December, 1972.     

左旋四氢巴马汀加强电针对兔大脑皮层牙髓诱发电位的...

Cortical potentials evoked by stimulation of the contralateral tooth-pulp were recorded epidurally from the SI cortex of rabbits anesthetized with urethane and chloralose. It was found that nociceptive components of the evoked potential consisted of P1 and P2 wavelets with a relative stable peak latency of 22.5 +/- 1.2 ms and 66.1 +/- 1.9 ms respectively. Higher intensity of tooth pulp stimulation was required for appearance of P2 than P1. Diazepam, a non-analgesic sedative, reduced P1 but not P2 amplitude. On the contrary, dolantin, an analgesic, suppressed P2 but showed no significant influence on P1. The results suggest that P2, but not P1 might be related to pain. The effects of l-tetrahydropalmatine (1-THP) and electroacupuncture on P2 were observed on 12 animals. The results showed that both iv l-THP 8mg/kg and electroacupuncture brought forth a decrease in P2 amplitude by 40.3 +/- 14% and 59.3 +/- 10% respectively, while electroacupuncture combined with l-THP produce a further decrease in P2 amplitude by 92.8 +/- 7%. Furthermore, the inhibitory periods of P2 amplitude were significantly prolonged after electroacupuncture combined with l-THP. The results indicated that l-THP enhanced the suppression of P2 by electroacupuncture.     

The functional testing of the interhemispheric asymmetry in the spatial organization of rabbit cortical potentials]

Interhemispheric asymmetry was studied of spatial-temporal potentials organization (STPO) of the cortex in non-fixated animals in the states of deep rest, behavioural activity and in the transition period between them. Despite the intrahemispheric differences of the STPO in each of these states, interhemispheric divergences in the character of reconstructions of momentary topograms of the cortical potentials, recorded at 24-channels leading, are limited by 35% of the epoch analysis time. Comparison of the dynamics of intrahemispheric changes of topograms of cortical potentials in the left and right hemispheres in the states of rest and activity revealed a narrowing of temporal period of the absence of resemblance in reconstructions of successive topograms of the left and right hemispheres in comparison with transition processes. In the phase of rest the interhemispheric conjugation of spatial reconstructions in topograms became lowered mainly because of the disturbances of monotony of changes of their reliefs in one of the hemispheres in turn. In the active phase, deviations from STPO of the cortex, characteristic of the state of rest, were met more frequently in the right hemisphere; in that case oscillations of the topograms general mean level connected with the activity of non-specific activating subcortical brain system acquired a significant role in regulation of interhemispheric relations. Presence of interhemispheric resemblance of reconstructions of topograms reliefs in the active phase, despite the tendency to its lowering in comparison with the rest, testifies to the contribution also of the intracortical processes to the interhemispheric spatial synchronization of the cortical potentials in this state.     

Comparative effect of thiopental sodium on cortical evoked potentials of different origin

The minimal doses of thiopental sodium (TS) to suppress each of seven varieties of cortical evoked potentials tested were determined in experiments on cats. The preparation had the strongest effect on the following responses: interzonal, arising in the motor cortex to stimulation of somatosensory area I; the reflex pyramidal and late components of the direct pyramidal response. The oligosynaptic transcallosal potential is less sensitive than the above responses but more so than the callosal response. The action of TS on the response depends on the complexity of its organization. The level at which the given cortical response takes place must also be considered. Comparison of the action of TS on the I₁ wave of the pyramidal response and on the dendritic component of the direct cortical response showed that, given equal complexity of its organization, the response arising in deep layers of the cortex is depressed more by TS than the response arising wholly at the level of surface layer I.Institute of Pharmacology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 4, No. 3, pp. 264–271, May–June, 1972.     

The functional significance of synchronization of cortical potentials in humans

The dependence between the level and the topography of spatial synchronization of cortical potentials and the manifestation of motor reactions to light stimuli was studied in humans. To evaluate the spatial synchronization of potentials the correlation coefficients () were calculated between three points of the motor area and each of three occipital points of the cortex. The calculation was made using a computer with direct input of the potentials. At a definite level of the machine switched on a light stimulus and a mechanism recording the motor reaction. The experiments have shown that the higher the number of pair derivations giving a high value of , the more often movements are caused. Moreover it became apparent that the pattern of correlation ratios between the derivations depends on the motor reactions. In the case of movements a significant constancy of the ratios between individual derivations was found. It is shown that the spatial synchronization of potentials in the human cerebral cortex has a functional significance. However, this synchronization does not reflect the realization of movements but only the conditions required for them.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 2, No. 2, pp. 166–172, March–April, 1970.     

Somatosensory evoked potentials by tibial nerve stimulation in the rabbit

Somatosensory evoked potentials by tibial nerve stimulation were obtained in ten New Zealand rabbits. The subcortical or cortical source of the three negative and three positive peaks present in the first 55 ms is discussed viewing the results obtained by different surface electrode locations and by stereotaxic recordings. The authors report interanimal, interhemispheric and test-retest variability of latencies and amplitudes of subcortical and cortical components.     

The influence of emotionally significant visual stimuli on cortical evoked potentials

Electrophysiological correlates of the perception of emotional stimuli were studied by means of recording the visual evoked potentials (EP) in 20 derivations (Fz, Cz, Pz, Oz, Fp _1/2,F _3/4,F _7/8,C _3/4,P _3/4,T _3/4,T _5/6, andO _1/2) during the emotional test performance. The performance of a special task by subjects was assessed positively or negatively (by administering emotionally positive or negative stimuli, respectively). Factor analysis revealed seven factors, which described the EP component structure. Analysis of variance demonstrated the influence of the emotional stimuli sign on the factorsP ₁₀₀,P ₁₄₀,N ₁₆₀,P ₂₂₀,P ₃₄₀, and “slow wave.” Hemispheric difference in reactions to the stimuli of a different emotional sign were recorded. During presentation of the positive and negative assessments, the amplitudes of the factorsP ₁₀₀,P ₃₄₀, and “slow wave” were maximally different in the left hemisphere, while the factorsN ₁₆₀ andP ₂₂₀ were maximally different in the right hemisphere.