[A mathematical model of neuronal plasticity].

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 active electrogenesis of the command neurons in the defensive behavior of the mollusk during conditioning].

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.

[Independence of the process of habituation from protein synthesis in the mollusk neuron].

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.

[Possible relation between learning and non-template RNA synthesis in neurons].

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.

[Mollusk neuron habituation following extra- and intracellular administration of an ACTH fragment].

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).

[Divergent effect of acetylcholine on processes of habituation and disinhibition].

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.

[Selective decrease in neuron excitability during habituation].

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.

[Changes in the postsynaptic and spike potentials of a cortical neuron during habituation].

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.

[Selective reduction of the amplitude of the action potentials of neurons in the process of habituation].

Spike discharges of single neurons in the forebrain general cortex of the turtle were recorded extracellularly during habituation to light flashesmthe amplitude of spontaneous spikes, short-latent evoked spikes and spikes after the inhibitory pause was measuredmthe amplitude of short-latent evoked spikes significantly decreased during habtiuation while the background and postinhibitory spikes remained unchanged. It is supposed that the pattern of synapses activated by a definite stimulus may change the state of the elcetrically excitable neuronal membrane during habituation