[A mathematical model of neuronal plasticity]. / Matematicheskaia model' plastichnosti neirona.

A model of the neuron is proposed which is capable of learning with a teacher. The model is based on hypothetic chemical processes which can proceed in a real nerve cell. It is shown that such model having O(N2) elements of the memory is capable of dividing in two classes O(N2) of different input images, where N is the dimensionality of the input vector.

Active electrogenesis of command neurons of defense behavior of the snail during conditioning.

A change in the active electrogenesis of command neurons of the defensive closing of the spiracle of the edible snail during the development, extinction, and repeat development of a classical conditioned defense reflex in response to tactile stimulation is described in this study; the tactile stimulation of another point of the body served as the differential stimulus. As the biological significance of the conditional stimulus increased as the result of training, the excitability of the command neurons in response to this stimulus increased. At the same time, the neurons manifested reduced excitability in response to the differential stimulus. The possible mechanisms of the rapid reorganization of the excitability of the neurons and the functional significance of the change in the generation threshold of the AP are discussed.

[The active electrogenesis of the command neurons in the defensive behavior of the mollusk during conditioning]. / Aktivnyi élektrogenez komandnykh neironov oboronitel'nogo povedeniia molliuska pri obuslovlivanii.

In the paper changes of active electrogenesis of the command neurones of defensive closure of snail pneumostome at elaboration, extinction and repeated elaboration of classic conditioned defensive reflex to tactile stimulus was described; the tactile stimulation of other point of the body served as a differentiating stimulus. During the increase of biological significance of conditioned stimulus as a result of learning the stimulation of the command neurones in response to this stimulus was raised. At the same time the neurones showed decreased excitability in response to differentiating stimulus. Possible mechanisms of quick reconstruction of neurones excitability and functional value of PA generation threshold changes were discussed.

[Independence of the process of habituation from protein synthesis in the mollusk neuron]. / Nezavisimost' protsessa vyrabotki privykaniia ot sinteza belka v neirone molliuska.

The influence of protein synthesis blocators--puromicine and gougerotine--on the dynamics of habituation to repeated tactile stimuli in mollusc's neurones was studied microionophoretically. Dynamics of habituation was judged by reduction of impulses number in neurone's response, increase of thresholds and latency of the first synaptic action potential in the response to repeated stimuli. Introduction of the substances produced the greatest effect on the dynamics of thresholds. Puromicine introduction suppressed the habituation only if it was accompanied by generation of epileptiform activity. Gougerotine improved the habituation in the animals with initially weak process. The obtained data testify to the hypothesis that protein synthesis blockade does not impede the process of habituation.

[Possible relation between learning and non-template RNA synthesis in neurons]. / Vozmozhnaia zavisimost' obucheniia ot nematrichnogo sinteza RNK v neironakh.

A substrate of either matrix-(cytidinetriphosphate, CTPh) or non-matrix (cytidinediphosphate, CDPh, or uridinediphosphate, UDPh) RNA synthesis was injected into mollusc neurone by means of intracellular microionophoresis. Subsequently, habituation was elaborated, assuming that if this process depends on the RNA synthesis, then the formation of defective RNA molecules with an excessive content of cytidine or uridine will disturb the learning process. In control experiments, habituation was elaborated either without drugs administration or following an injection of cytidinemonophosphate non subject to polymerization, or of an equimolar mixture of four ribonucleotidediphosphates: CDPh+UDPh+ADPh++GDPh. In the latter case a minimal distortion of the ratio between the initial substrates of the non-matrix RNA synthesis was expected. Both in the control experiments and following CTPh administration, the habituation was attended with an increase of threshold and latencies of spikes evoked by repeated stimuli. Injection of CDPh or UDPh disturbed the dynamics of thresholds and latencies increase in the course of habituation. The data obtained suggest that the habituation process is connected with a non-matrix synthesis of RNA in the neurones.

[Mollusk neuron habituation following extra- and intracellular administration of an ACTH fragment]. / Privykanie u neironov molliuska posle vne- i vnutrikletochnogo vvedeniia fragmenta AKTG.

By means of intracellular recording of the mollusc neuronal activity a study was made of the influence of ACTH4-7--a fragment of the stress hormone,--on elaboration of habituation to tactile stimuli. ACTH was administered immediately after the elaboration of the series I of habituation (25 to 30 stimuli) by means of either perfusion or extra- or intracellular microionophoresis. This was followed by the II-V habituation series (with 15 min intervals between them). Perfusion and extracellular (not intracellular) ACTH4-7 administration produced an acceleration of habituation in the series II, increase of action potentials (AP) thresholds in the response to the first tactile stimulus of series II and cessation of further increase of the AP thresholds in the course of elaboration. Without ACTH, these phenomena were observed beginning with habituation series IV. The ACTH action while influencing the memory is apparently directed to the external side of the excitable neuronal membrane; ACTH seems to accelerate the consolidation process. Any of the methods of ACTH administration produced also an enhancement of EPSPs and an increase in the number of APs in the responses to stimuli, without lowering the thresholds of APs generation. This testifies toi enhanced chemosensitivity of the membrane and may underlie the influence of ACTH on the level of wakefulness.

[Divergent effect of acetylcholine on processes of habituation and disinhibition]. / Raznonapravlennoe vliianie atsetilkholina na protsessy privykaniia i rastormazhivaniia.

The elaboration of habituation to repeated tactile stimuli was studied in snail (Helix pomatia) by means of intracellular recording of the neuronal activity and microionophoresis of acetylcholine (ACh). Light or a stronger tactile stimulation served as extrastimulus. The elaboration of habituation was accompanied by a rise in the threshold of action potentials (APs) generation, evoked by the habitual stimulus, and by a lowering of the threshold of APs elicited by the extrastimulus. Prior to the habituation neuronal responses to tactile or photic stimuli did not change against the ACh background. After habituation was elaborated the ACh administration led to disinhibition of responses to the habitual stimulus (in particular, the AP threshold became lower), and to a decrease in responses to the extrastimulus (AP threshold rose). It is assumed that hibituation changes the chemical responses caused in the neurone by the activation of both the pool of synapses, corresponding to the habitual stimulus, and the pool of synapses corresponding to the extrastimulus. These changes, however, are of a qualitatively different character.

[Selective decrease in neuron excitability during habituation]. / Izbiratel'noe snizhenie vozbudimosti neirona v protsesse privykaniia.

By means of the intracellular recording a study was made of the habituation to tactile stimuli in Helex pomatia neurones and of the influence of acetylcholine (ACh) microionphoresis on the response to a habituating stimulus in those units which before habituation reduced the reaction to a tactile stimulus under the action of ACh. Habituation was attended with a diminution of EPSP and of the action potential (AP) elicited by the habituating stimulus. The AP generation threshold and the probability of AP blockade increased with stimuli repetition. An extra stimulus produced in the neurones a greater AP at a lower threshold. After habituation elaboration, Ach increased the neurone response to the habituating stimulus: EPSP and the probability of AP generation increased, while the AP threshold was lowered. At the interaction of the activated synapses with the neurone, the electrogenic and chemical properties of its membrane may probably change for a short time so that the threshold and the AP and EPSP amplitude may differ for the stimuli with different biological significance.

[Changes in the postsynaptic and spike potentials of a cortical neuron during habituation]. / Izmenenie postsinapticheskikh i pikovykh potentsialov korkovogo neirona v protsesse privykaniia

Changes in the spikes, EPSPs and IPSPs of neurons in the general cortex of the turtle forebrain were studied intracellularly during irregular repetition of light flasches. The amplitudes of these intracellular potentials decreased during habituation without any change in the resting potential. Their dependence on the membrane potential level changed. The short-latent evoked spikes decreased more considerably as compared with the spontaneous spikes and the spikes after IPSP. Probably, the decrease of the spontaneous spike and the spike after the IPSP reflects a nonspecific decrease in the excitability of a neuron because of the long intracellular recording so far as during extracellularly recording only the short-latent evoked spike decreased with habituation. The decrease of the short-latent evoked spike reflects neuronal habituation. A disinhibition of spikes and PSPs was observed. A suggestion is advanced that the pattern of synapses activated by a definite repetitive stimulus evokes a transitory change of the electrogenic properties of the neuronal membrane.