Intralimbic evoked potentials in the formation of an instrumental food conditioned reflex to hippocampal electrostimulation in dogs]

In dogs with the electrodes implanted in the hippocampus, amygdala, septum and hypothalamus an instrumental alimentary conditioned reflex (CR) was elaborated to electrostimulation of the hippocampus. Intralimbic evoked potentials (EPs) were studied during the elaboration and extinction of this reflex and during stimulations of limbic structures conducted with the purpose of CR generalization checking. Late EP components in the lateral hypothalamus and central nucleus of the amygdala changed during CR elaboration and extinction and in the hippocampus during amygdala testing. In both cases the amplitude of trace positivity and of slow negative wave was less, when during stimulation of the structure an instrumental movement was initiated than at its absence.     

Conditioned modification of viscerosensory evoked potentials during sleep and wakefulness in cats

The effects of classic conditioning on the viscerosensory evoked potentials (EPs) were studied in twenty cats during wakefulness (W), slow-wave-sleep (SWS) and paradoxical sleep (PS). Four types of the experiment were performed on four groups of animals. Weak, non-painful stimulation of the small intestine or of the left splanchnic nerve was used as conditional stimulus (CS) in all experiments. A painful or non-painful shock on the left radial nerve served as unconditional stimulus (US) which followed the CS with a delay of 500 ms. In the first and second series of experiments, the CS was paired with non-painful or painful CS during W. In the third and fourth types of experiment, weak US was used and conditioning was done during SWS or PS. The evoked responses were recorded from the primary (SI) and secondary (SII) somatosensory and associative (AS) cortex, the thalamus (VPL), hypothalamus (HPT) and dorsal hippocampus (HPC). In each experiment, the stimulus pairings resulted in a complex electrographic conditional response (CR) which included an amplitude increase of the late components of EP's (early CR) and the development of a wave of 500 ms latency (delayed CR). In the second experiment, however, a behavioural CR (limb flexion) also appeared. All these CRs proved to be extinguishable. The recall of CR established during W was successful in SWS. The traces of CS-US pairings during SWS could, however, be elicited only in SWS. Both establishment and recall of CR were unsuccessful during PS. The possible mechanism of the effects originating from an interaction of conditioning and sleep on the viscerosensory inputs of the brain are discussed.     

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.     

Changes in the jaw-opening reflex during anesthesia resulting from auricular electrostimulation

The effect of auricular electrostimulation on the jaw opening reflex and affective behaviour of adult cats was studied in chronic experiments during stimulation of the lip. Auricular electrostimulation was shown to facilitate the jaw opening reflex and to inhibit the affective component of the pain.     

A collector of evoked potentials]

The collector is an adaptive algorithm for pattern recognition. It proposes new in-line fully-automatic technique to learn and recognize effective patterns of input data stream. Evoked potentials (EP) were recorded by ADDA 100 KHz, 4 channels, and described by 200 points per each EP. The collector recognized different studies of conditioned response (CR) by patterns of EPs in amygdalar central nucleus. In dogs with implanted into the limbic structures concentric electrodes an instrumental CR was elaborated to electrical stimulation of the dorsal hippocampus. Generalization or transfer of this CR was tested by means of electrostimulation of amygdalar basal nucleus. The generalization in the first experiment took place approximately in 86% of cases, in the second one in 52% of cases. In the first experiment the amplitudes of initial negativity and of late positive waves were smaller than those in the second one and in the experiments before conditioning.     

Changes in visual evoked potentials after phosphene electrostimulation in children suffering from myopia

We recorded visual evoked potentials (VEPs) in children suffering from medium and high myopia (3.0 to 6.0 and more than 6.0 D; 28 and 21 patients, respectively); a light flash was used as the stimulus. The VEPs were recorded before and after a curative course of phosphene electrostimulation (PhES; frequency 15 sec⁻¹, 10 to 15 10-min-long everyday sessions). The above course resulted in clear trends toward decreases in the peak latencies of the P60 and P100 VEP components; changes in the latencies of other components were expressed to a lesser extent. In children with medium myopia, the latency of the P60 component decreased, on average, by more than 21% (P < 0.05); in patients with high myopia, the respective decrease was about 12% (P > 0.05). These shifts were accompanied by increases in the mean amplitudes of the P60 and, to a lesser degree, P100 (more expressed in medium myopia). The data obtained allow us to suppose that the PhES course provides increases in the transmission velocity through relay structures of the visual analyzer and in neuronal networks of the visual cortex and also in the number of neuronal units whose activity is reflected in generation of VEPs. Application of the PhES technique is much more effective in relatively moderate myopia. Neirofiziologiya/Neurophysiology, Vol. 40, No. 3, pp. 228–235, May–June, 2008.     

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.     

Turnover of chromatin proteins in rat liver during induction of RNA synthesis by electrostimulation of the hypothalamus

It has been shown that the induction of D-RNA synthesis in rat liver nuclei by electrostimulation of hypothalamus is accompanied by a decrease in chromatin protein synthesis and an increase in phosphorylation and acetylation of chromatin proteins. The decrease of the histone synthesis is mainly due to the decrease of [14C]lysine and [14C]alanine incorporation into histones H1 and H4. The relationship between H1, H2b-H3, H2a and H4 histone fractions remains unchanged. Electrostimulation of hypothalamus increases acetylation of H2a and H4 histone fractions and phosphorylation of all histones with the exception of histone H1.     

Morphofunctional restructuring of the nervous system of the lymphoid organs during electrostimulation of the hypothalamus

The intramural nervous apparatus of rabbit lymphoid organs was examined after 15 and 30 sessions of electric stimulation of the posterior hypothalamus. The function of nerve cells was evaluated by cytophotometry according to the content of catecholamines and acetylcholinesterase (ACE) activity. In the mesenteric lymph nodes, stimulation led to a decrease in the activity of both adrenergic and ACE-containing nerve cells. The spleen demonstrated a reduction in the catecholamine content in the perivascular nerve plexuses, with a simultaneous rise of the catecholamine content in the fibers located in the parenchyma, which evidences inhibition of the neurogenous mechanisms of vasomotor control and possible selective activation of the sympathetic mechanisms involved in the regulation of the immunogenesis. Thymic preparations impregnated with silver salts manifested high argyrophilia of the nerve cells, characteristic of the reactive phase of the destructive process. The problems of the hypothalamic effects on the blood supply and functions of the immune system organs are discussed.     

Conditioned reflex activity and several vegetative reactions in dogs during the recovery period following repeated reanimation]

Conditioned activity and vegetative reactions were studied in dogs which repeatedly underwent clinical death from electrical trauma and were reanimated by donor artificial blood circulation. (The first clinical death was provoked 15 to 18 months prior to the repeated death and was caused by drowning and blood loss). On the first few days after reanimation the functions of the higher parts of the CNS and the vegetative nervous system were considerably disturbed. This was manifested in diminished effector reactions to conditioned stimuli, in narcotic and ultraparadoxal phases in conditioned activity, in tachycardia and a higher respiratory rate. The disturbances gradually diminished and by the 5th to 13th day following reanimation completely disappeared. The nature and depth of the disturbances correlated with the basic properties of the animals' type of higher nervous activity. The conditioned reactions were restored despite the retained pronounced dystrophic and destructive changes in the cerebral cortex. This is significant proof of important compensatory capacity for conditioned activity in dogs.     

Mouse auditory sensitivity as measured by averaged evoked potentials]

The audition of four strains of mice was determined with summated auditory evoked potentials at the inferior colliculus level. One of these strains was completely deaf. For the 3 others a specific auditory sensitivity was found with statistically different thresholds. But, for these, the best sensitivity is around 16 kHz. Two of them show a flattening of the curve between 32 and 64 kHz. This range corresponds to the ultrasounds emitted by the pups.