Electrophysiologic correlates of habituation and conditioned reflex elaboration

The average correlation coefficient between the EEG of different parts of the cortex gradually decreases as the rabbit is habituated to the experimental surroundings. Elaboration of an electo-defensive conditioned reflex leads to its enhancement which is replaced by a phase of temporary decrease, to be followed again by an enhancement of EEG correlation. The pronouncedness of theta-frequencies in the spectral and coherent functions behaves in a similar way. Successive changes of delta-activity level reveal no regularity.     

Evoked potentials during the elaboration of a conditioned reflex to hippocampal stimulation in rats

In experiments on 9 rats, the study of evoked potentials (EPs) of the CA1 field of the dorsal hippocampus to stimulation of its symmetrical part serving as a signal of drinking conditioned reflex (CR) showed that during reflex elaboration, the amplitude of the main EP components significantly decreased; CR did not appear when the population spike (PS) was absent in the hippocampal response. PS always accompanying CR was not specific only of it, it was also recorded at other behavioural reactions. Changes of fascia dentata EPs in the process of CR elaboration to stimulation of its symmetrical part consisted in decrease of the initial negative wave and increase of the positive one. The obtained data point to a significant reconstruction of excitatory and inhibitory inputs to the hippocampus and fascia dentata under the influence of conditioned activity.     

Contribution of serotonin to establishing a conditioned food aversion reflex in the snail

Combined presentation of food and noxious electrical stimulation produced no response in snails injected 6–16 days previously with 5,7-dihydrooxytryptamine, which produces degeneration of serotoninergic nerve terminals and reduced serotonin synthesis, although a defense (aversive) response was observed in the control group. Application of serotonin to a preparation of the snail central nervous system (contained in a bath) was used as reinforcement during neurophysiological experiments. The amplitude of synaptic response to nerve stimulation increased significantly in preparations in which stimulation was paired with serotonin application. After 3–7 sets of twin stimuli consisting of serotonin application and applying a drop of juice to the chemoreceptive surface area of the skin, a spike response to the latter stimulus was produced. No such effects were seen in response to unpaired stimuli. It was deduced that serotonin makes a major contribution to establishing conditioned aversive reactions in the snail.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 18, No. 3, pp. 291–298, May–June, 1986.     

Regression analysis of an instrumental conditioned tentacular reflex in the edible snail

Regression analysis revealed the opportunity of approximation with exponential mathematical model of the learning curves of conditioned tentacle reflex. Retention of the reflex persisted for more than three weeks. There were some quantitative differences between conditioning of the right and the left tentacle. There was formation of the reflex in every session during spring period, but there was no retention between sessions. The conditioned tentacle reflex may be employed in neuropharmacological studies.     

Evoked potentials during elaboration of fine differentiations

The paper deals with the character of changes in the EP form recorded from the visual cortex of a rat during elaboration of a system of positive and negative (with different degree of precision) conditioned defensive reflexes. It has been shown that in a state of a consolidated habit of pain stimulus avoidance in a shuttle box a negative component with peak latency up to 70 msec develops in EP to the differentiation stimulus of 0.5 c/s. This component is much less pronounced to the 2 c/s conditioned stimulus. When a more precise differentiation stimulus (1 c/s) was presented to the animal in this state the development of the studied component depended on the subsequent behavioural reaction: it developed if the animal reacted in the same way as to the differentiation stimulus. This fact suggests that the generation of this component is connected with the inhibitory processes developing at the time when the animal is choosing its behavioural reaction.     

Fromation of forward and reverse connections during elaboration of a classical and instrumental acid-defense conditioned reflex

During elaboration of a classical acid defensive conditioned reflex to passive lifting of a foreleg in dogs, the reinforcing stimulus--acid elicited an extension of the leg via backward connection. At the initial stage of elaboration of an instrumental avoidance reflex, the reinforcing stimulus called forth an extension of the leg, whereas at the stage of a stable reflex it produced a flexion.     

Changes in active 14C-noradrenaline uptake by cerebral synaptosomes during elaboration of a conditioned reflex]

It was shown that active noradrenaline-14C (NA) uptake by the rat brain synaptosomes is inhibited by ouabain (0.1 M) and K-depolarization. Acquisition of the defensive conditioned reflex leads to inhibition of active NA uptake by the synaptosomes. This effect may be connected both with changes in the presynaptic membrane state and possible enhancement of the postsynaptic adrenoreceptor function.