Changes In Conditioned Reflexes Research Articles

The correlation between changes in synaptic efficiency and cellular excitability during the development of a conditioned reflex analog.

The calculation of the coefficient of correlation between changes in the direct (D) and monosynaptic (I) components of the pyramidal tract (PT) response made it possible to establish the presence of a positive linear association between conditioned reflex changes in synaptic efficiency and the shifts in cellular excitability observed at the same time. The coincidence of the maximal strength of this association with the greatest increase in cellular excitability which is dependent on the activation of motivatiogenic structures points to the role of these subcortical structures in the launching of intracellular reactions which leads to the formation of the overall molecular substrate which underlies interaction of membrane and synaptic mechanisms. The preceding of the greatest enhancement of synaptic efficiency by the maximal manifestation of the interaction attests to the contribution of this process to the manifestation of the principal mechanism of the conditioned reflex (CR).

The influence of microiontophoretic application of acetylcholine on the formation of conditioned reactions of neurons of the motor cortex

The activity of neurons of the motor cortex with simultaneous application to them of acetylcholine was recorded in awake rabbits in the process of the development of a conditioned defense reflex. The conditioned reflex changes were found primarily in cholinosensitive neurons. It was shown that iontophoretic application of the mediator promotes the establishment of the conditioned neuronal responses and leads to an increase in their magnitude as compared with reactions recorded in the absence of acetylcholine. It is hypothesized that the influence of acetylcholine on the conditioned reflex cellular process is accomplished through an effect on the state of excitability of the cortical neurons.

Conditioned reflex changes in relations between afferent inputs from the lateral geniculate body and pulvinar in the cat visual and association cortex.

1. An alimentary instrumental conditioned reflex to electrical stimulation of the lateral geniculate body and pulvinar (LGB and P) can be formed, extinguished, and restored irrespective of whether the LGB + P or P + LGB combinations of stimuli is used. 2. If LGB is stimulated 40 msec beforehand, facilitation of the response in VC and AC to testing stimulation of P, observed in untrained cats, is inhibited when the reflex to stimulation of LGB + P is consolidated; moreover, a considerable increase in amplitude of the response to conditioning stimulation of LGB, takes place. 3. If P is stimulated 40 msec before LGB during conditioning to stimulation by the P + LGB combination, in the middle of training facilitation of the response to testing stimulation of LGB is observed in both VC and AC, with a simultaneous increase in amplitude of the response to conditioning stimulation of P, although these changes are not found when the reflex is consolidated. 4. During perception of a monomodal complex conditioned stimulus relations between individual cortical inputs are modified within the same analyzer.

Conditioned reflex activities and nervous system type in revived dogs

Dogs were revived from clinical death from electroshock for 15–16 min, and from apnoea 19–20 min after cardiac arrest, by means of artificial perfusion or a donor animal. Changes in conditioned reflexes were found for 6–9 days after resuscitation, but they reverted to normal completely by the fifteenth to eighteenth day. The dynamics of conditioning and recovery were studied using the secretory method in dogs which recovered from clinical death after electroshock, drowning and haemorrhage, but they showed no lasting functional pathology.

Cell analog of the conditioned reflex to cortical electrical stimulation.

The possibility of obtaining a cellular analog of a CR was investigated on the sensory motor cortex of the unanesthetized rabbit. Single unit activity was analyzed. Stimulation through surface cortical electrodes 2.5–12mm away from the recording microelectrode was used as the conditional stimulus (CS). The unconditional stimulus (US) was stimulation through two closely situated electrodes. With short (1–5 sec) inter-trial intervals, and with a US of sufficient strength and duration, a well-marked augmentation of the excitatory response to CS was obtained in most neurons. However, it was short (less than 30 sec) and, as a rule, it was the analog not of a CR but of a pseudo conditioned reflex, for it did not require pairing of the CS and US, but appeared after one or a few presentations of the US alone. In 9 of the 21 neurons tested with longer intervals between trials (7–120 sec) conditioned-reflex changes were observed. These changes consisted of the appearance (or modification) of a response to the CS during conditioning trials and disappearance during extinction trials, or of the appearance of a response at the time corresponding to the missing US when the US was intermittently omitted. The character of the conditioned-reflex changes (activation or inhibition) was the same as that of the cell's response to the US. Changes appeared after the first 10–20 conditioning trials and recovery after extinction took place more rapidly than initial conditioning, i.e., in 5–10 combinations.

Cholinergic Brain Mechanisms and Behaviour

This chapter discusses some of the problems related to the participation of cholinergic mechanisms in behavior. A number of workers have demonstrated the participation of cholinergic mechanisms in behavioral reactions. Also, a series of experiments have been performed on animals. An auditory signal was combined with an electric shock delivered through the grid floor. Fear reaction was well established after 3 or 4 combined stimuli and was expressed by the following symptoms: the animal stood stock still with the head drawn in, eyes closed and ears retracted. Urination and defecation were commonly observed. Most or the existing hypotheses on neurohumoral behavioral mechanisms are based mainly on changes in food and defense conditioned reflexes under the effect of adrenergic and cholinergic drugs. Data on the changes in conditioned reflexes under the effects of these agents cannot serve as proof that defensive responses are adrenergic or that food responses are cholinergic in nature. All the drugs stimulating the chemoreactive brain structures in low doses intensify conditioned responses. Large doses inhibit conditioned reflex activity and depression of food conditioned responses is observed. In intermediate doses, agents stimulating cholinergic and adrenergic brain structures raise the conditioned reflexes but do not modify the electroencephalogram (EEG) or behavior.

On the role of the cerebral cortex in the functional interrelationships between the mammary gland and the digestive system

The contractile function of all the portions of the multilocular stomach of ruminants enhances in stimulation of the gland receptors. Phenomena of external inhibition of the mentioned reactions were revealed. By combining mechanical stimulation of the mammary gland receptors with conditioned sound stimulus (bell) it was possible to obtain conditioned reflex changes of the contractile function of the reticulum, paunch, omasum and abomasum. The mentioned reactions are subject to extinctive and differential inhibition. Consequently, an important role in the functional interrelation of the mammary gland and digestive system belongs to the cortex of the large cerebral hemi spheres.

The Neoplastic Process and the Nervous System

This book consists of a historical review of numerous experiments conducted in Russia. Briefly, the thesis is developed that whatever the etiologic agents of malignancy may be, the disposition of the organism which permits the development of neoplasia is dependent upon endocrine balance, metabolic balance, and —most basic of all—the nervous system. Several chapters include data concerning changes in conditioned reflexes during tumor growth. One might logically expect to find alterations in the physiological activity of local and systemic nervous structures associated with tumor growth, but the question of which injury occurs first is left unanswered. In some of the experiments, the procedures used to alter the nervous system probably affected tumor growth, as might be expected from any general stress condition. Many of the experiments are interesting because they are so different from those performed in other countries. It is difficult to evaluate them without knowing more about the

The effect on cardiac reflexes of removal of the chromaffin tissue.

Conditioned reflex changes of the rate and intensity of the cardiac contractions were altered by the removal of the adrenal medulla. Studies were made on chronic preparations of dogs having a pericardial fistula. The conditioned cardiac reflexes were reduced or disappeared completely at the third, fourth, and fifth postoperative days. The amount by which the amplitude of the contractions changed in response to the stimulus was different on the fifth and sixth postoperative days. The changes were phasic: first there was a reduction, then an intensification, and finally a gradual re-establishment of the preoperative level. In response to an unconditioned stimulus, the failure of the normal increase in cardiac contractions was more marked and prolonged. The removal of the adrenal medulla had no significant effect upon the elicitation of an increased heart rate.

441b Drug induced changes in conditioned reflexes

441b Drug induced changes in conditioned reflexes

Search for Immediate Effects of X-Radiation on Frog Nerve-Muscle Preparations

For more than thirty years there have been reports of the effects of ionizing radiations on nerves and muscles. In the U. S. S. R., in particular, there has been considerable attention paid to these problems, but workers in other countries have contributed occasional important studies. Since such reports form the basis on which we designed our program and since there has been no recent adequate account of them other than by Russian-speaking authors, we review briefly a selection of recent published work to illustrate the considerations involved. Much of the Russian work in the field has been summarized in papers given at the second Geneva Conference on the Peaceful Uses of Atomic Energy (1-5). Most of the relevant studies mentioned in these papers concern changes in conditioned reflexes in various animals after whole-body or partial-body irradiation. For example, secretion of saliva in response to conditioned and unconditioned stimuli before and after whole-body irradiation with 250 r was studied by Fadeeva, Kurtsin, and Golovskii (quoted by Gorizontov, 4) in dogs with Pavlov stomachs; hypo- and hypersecretion were observed after irradiation, depending on the conditions. Yanson (quoted in 4) studied the increased rate of respiratory rhythm associated with a defensive conditioned reflex elicited in rabbits; he found that after 500 r to the whole body or to the head of the rabbit the rate fell sharply and remained low for some days. Many other such results are also referred to in the papers cited. Some studies have been made of the electrical activity of the higher nervous centers after irradiation. Lee et al. (6) stimulated the sciatic nerve of cats to evoke a cerebellar response which they recorded with electrodes touching the pia mater; the amplitude of the response began to diminish after a dose of about 6 kr had been given, and the effect was severe after 10 kr. The response continued to fall for 10 to 30 minutes after irradiation had ceased. Various changes after irradiation have also been reported in electroencephalograms (2, 7).

Conditioned reflex changes in the human electroretinogram

The conditioned reflex changes were formed in the human electroretinogram. The ERG was registered with the aid of an active electrode soldered into the contact lens. The EEG of both occipital regions was registered simultaneously. Light (which gave about 600 lux illumination on the pupil) served as an unconditioned stimulus. Sound served as conditioned stimulus (60 decibel over the threshold of hearing, 250 cycles per sec) which had no effect by itself on the ERG. Numerous combinations of this sound with the light stimulus brought about the development of conditioned reflex changes in the ERG. This was manifested by the fact that in response to the mild light stimulation, preceded by sound, the amplitude of the electroretinographic wave “b” became higher than in response to the weak stimulation by light alone. In both cases the light which was employed as a stimulus gave an illumination on the pupil equal to about 80 lux and the wave “b” the amplitude of which was much lower than in light stimulus with 600 lux. The conditioned reflex changes were simultaneously observed in the EEG.

Conditioned reflex changes in the mobility of the cold receptors in the skin

The level of the mobilization of the cold receptors changes not only under the effect of adequate stimuli, but under that of inadequate ones as well, provided the latter are combined with the adequate stimuli.