Dynamics of the activity of rabbit visual cortex neurons during elaboration of elementary conditioned reflexes to time and association

Elaboration of a reflex to time (with omissions of stimuli) and of association; light--light + electrocutaneous stimulation of the paw was studied on neurones of the rabbit visual cortex. It was shown that by similarity of patterns of the discharge to a conditioned stimulus and to reinforcement, 83% of neurones reveal the formation of a reflex to time, and 57%--elaboration of association. Three ways of coding plastic reorganizations of the neuronal discharges are suggested; by the total number of spikes in the response, by the total sum of inhibitory periods, and by the pattern of the response. It has been found that in the reflex to time the early components of the response to the stimulus are reproduced during omissions; in elaboration of the association the late components of the discharge reaction to reinforcement are mainly repeated. Most cells with plastic reorganizations possessed polysensority and revealed discharge sensitization during habituation.     

Unitary activity in the cat motor cortex during a conditioned postural adjustment reflex

Unitary activity in the motor cortex (area 4) during a conditioned postural adjustment reflex was investigated in cats. Responses of the overwhelming majority of neurons connected with conditioned-reflex placing movements were activational in type. They consisted of several components and preceded the movements themselves by 50–600 msec. During realization of incorrect responses to presentation of a differential stimulus and of "spontaneous" interstimulus movements, the unitary responses were similar in direction but differed in their lower intensity and, in most cases, they appeared simultaneously with these movements. In the course of extinction both the conditioned-reflex movements and the corresponding unitary responses disappeared simultaneously. The technique of formation of a conditioned postural adjustment reflex suggested in this paper can be used to from natural, well-coordinated forelimb movements in animals in response to conditioned stimulation which are necessary initial components of more complex behavioral motor responses.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 745–753, November–December, 1984.     

Dopaminergic modulation of impulse activity of sensorymotor cortex neurons during conditioned reflex

Changes of conditioned impulse reaction of cortical neurons wer studied during microiontophoretic application of agonist and antagonists of glutamate and GABA transmission and their modulation by dopamine. It was shown paradoxal reaction of facilitation of impulse activity during iontophoretic application of ionotropic glutamate antagonist and depressive influences of metabotropic antagonist. Local iontophoretic application of dopamine increased background and evoked impulse activity of pyramidal neurons of deep layers of cortex and eliminated inhibitory influences of glutamate metabotropic antagonist MCPG. It is concluded that DA has stabilizing effects on activity of cortical neurons. It is suppose that these effects of DA realize through system of inhibitory interneurons.     

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.     

The assessment of the strength of the interaction between neurons of the cat motor cortex in a conditioned reflex to time]

The work was conducted on cats with recording multineuronal activity of the motor cortex at the elaboration of conditioned reflex to time. Strength of interaction was estimated between the adjacent and remote neurones in the limits of 0.5 m. The dynamics of strengths of interneuronal interaction in most cases did not correlate with the dynamics of impulses frequency of the studied neurones. Changes of strengths of interaction between mutually remote neurones at CRT were met more frequently than between the adjacent ones, what may serve as one more evidence of the hypothesis on more strict structure of connections within microsystems and greater plasticity of connections between microsystems.     

Activity of neurons of the motor zone of the cortex during elaboration of a local instrumental defensive reflex in the rabbit

During instrumental defensive reaction of wrist extension in response to a sound (conditioned) stimulus, two types of neuronal responses in the rabbit motor cortex were discovered. The first type was recorded in cells with activity not connected with electromyographic activity of wrist extensors. The reaction consisted in the appearance of inhibitory response at the place of the cancelled electrocutaneous stimulation at animal's performance of conditioned reaction to sound. The second type of responses was shown for a neurone with the activity significantly related to electromyographic activity. In this case the conditioned motor response was accompanied by enhancement of the cellular activation reaction to sound and the increase of spike activity in interstimuli intervals.     

Activity of anterolateral motor cortex neurons in instumental food-acquisition and alcohol-acquisition behavior

Singleunit activity of anterolateral area of motor cortex in rabbits subjected to chronic ethanol treatment was recorded to study interconnections of neuronal mechanisms of newly formed instrumental alcohol-acquisition behavior (IAB) and previously formed food-acquisition behavior (IFB). Adult animals were trained to perform IFB in experimental cage equipped with two food boxes and two pedals situated in the corners of the cage. Food was presented automatically in a food box after the pressing of an appropriate pedal. Same rabbits after 9 mo. of chronic alcohol treatment were trained to perform IAB in the same experimental cage (gelatin capsules filled with 15% ethanol solution were placed into the food box instead of food). Activity of 121 units of anterolateral area of motor cortex was studied. Each unit discharges were analysed in IAB as well as in IFB. The data obtained testifies that neuronal sets subserving IAB and IFB overlap but not completely. 44 "common" neurons permanently activated in both behaviors and 3 neurons specifically activated in each of behaviors (one in IAB and two in IFB) were found. We consider the formation of IAB as systemogenesis that is related to the consolidation processes: the formation of new neuronal specializations and to the accommodative re-consolidation: modification of early specialized cells ("common"). It is shown in the Discussion that present experiments help us not only understand interconnections of neuronal mechanisms of newly formed IAB and early formed IFB but also provide an additional insight into the nature of similarity between neuronal mechanisms of long-term memory and long-lived modifications resulting from repeated drug exposure.     

Function of the adrenal cortex during elaboration of the passive avoidance conditioned reflex in immature rats

Plasma 11-hydroxycorticosteroid (11-OHCS) levels were measured in 30-day-old rats by fluorometry during passive avoidance (PA) learning by means of a single electric footshock. In contrast to the data obtained in adult animals, pre-exposure of young rats for 7 days to the experimental environment (over 3 min daily) resulted in elevation of the basal 11-OHCS levels and in the lack of distinct changes in the hormonal background after placing the young rats into a chamber. As in previous experiments on adult rats, one day after PA learning the 11-OHCS levels were significantly lower in young rats displaying PA than in the animals which did not exhibit PA behavior. Five days after PA training these differences in adrenocortical reactivity disappeared, as was the case in adult animals.     

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.     

Functional assymmetry of the cerebral cortex in cats during formation of a conditioned reflex

During elaboration of a symmetric active defensive reflex, the animal is given the opportunity to make instrumental movements with the right or left paw. On the first day of elaboration, the cats can be subdivided into three approximately equal groups: with the right preferred paw, with the left preferred paw and ambidexters. After stabilization of the reflex, motor asymmetry increases in both preferred groups, while the number of ambidexters diminishes. Unilateral electric shock producing seizures, which is applied to the "dominant" or "subdominant" hemisphere, exerts correspondingly differing influences on the subsequent reproduction of the reflex. Suppression of reproduction is more pronounced when the shock is applied to the "dominant" hemisphere. The result of repetitive application of electroshock to one and the same hemisphere is that the functions of the "dominant" hemisphere are effected by the hemisphere which was not subjected to direct electrical stimulation.