Excerpts from Lectures on Conditioned Reflexes, Volume II: Conditioned Reflexes and Psychiatry
Ivan Petrovitch Pavlov
AN EXAMPLE OF AN EXPERIMENTALLY PRODUCED NEUROSIS AND ITS TREATMENT IN THE WEAK TYPE OF NERVOUS SYSTEM
(Read at the VI Scandinavian Neurological Congress, Copenhagen, August 25, 1932.
BROMIDES IN DIFFERENT TYPES OF DOGS – DESCRIPTION OF A CASE OF EXPERIMENTAL NEUROSIS.
AT THE International Neurological Congress in Berne last year I reported only the most general characteristics of our experimentally produced neuroses. Here I shall proceed to give an example of a neurosis which I have just now thoroughly studied with one of my oldest and most esteemed co-workers, M. K. Petrova.
When dealing with purely experimental neuroses we must begin with the question of types of the nervous system of animals (dogs). We differentiate three basic types: the strong, even very strong, and unbalanced; the strong and balanced, i.e., with the two opposite processes at the same level; and the weak.... There are of course varying degrees or variations of these types especially of the weak. We have a considerable number of experiments by which we have gradually defined these types and their grades. A correct diagnosis of type can be made only after repeated experiments.
The purely experimental neuroses, obtained by giving difficult nervous problems, have appeared only in animals of the extreme types. With them this condition may be readily produced in several ways. I shall describe here a case of repeated neurosis in a dog of the weak type.
This dog was a mixture of cur with foxterrier, weight about 12 kgm. According to the external behaviour, the work with the conditioned food reflex, and according to several of our experiments on this type, this animal appeared in the beginning as a strong and balanced animal; but two further experiments convinced us that he belonged to the weak type: first, there was an increased food excitability (on the day before the experiment the dog went without food), and second the administration of large doses of bromide placed him in the weak group. In animals of the strong type with an increased food excitability usually either the effects of all the conditioned positive stimuli increases (if the effects of the strong are not transmarginal), or in the opposite case, only the effects of the weak approach the strong.
Large doses of bromides given daily for many weeks or months have proved in our hands to be free of any harm; and in the strong and unbalanced types it even has a useful action, increasing their inhibitory function and then enabling them to regulate their nervous activity.
In our dogs both of these measures led to a diminution, to a destruction of the conditioned reflexes: the effects of the positive stimuli fail, but the negative continued to produce normal inhibition. In this case it was clear that with the gradually decreasing doses of bromide we could even improve the nervous activity. Formerly we came to an erroneous conclusion here: not regulating the dose of bromide correspondingly to the type, we thought that its administration in weak animals was never helpful and that in large doses it was injurious.
Thus our dog belonged to the weak type, but of moderate degree. Under the ordinary circumstances he works satisfactorily; a system consisting of six positive stimuli of different kinds and intensities and of one negative, applied daily in the same order and with equal intervals, always produces in this dog regular and correct responses. The behaviour of the animal during the experiment is more or less lively and equilibrated. In short it is a stable object for the study of conditioned reflexes. Such a condition was observed over a period of five months.
Now we produce the neurosis. Until now the inhibitory stimuli had acted only for thirty seconds. In the following experiment we prolong it for an entire five minutes. On another day we repeat the five minute inhibition, and this was enough to change radically the whole dog, to make him acutely ill.
Of the regularity of the conditioned reflexes there remains not a trace. Each day showed a characteristic picture. All the positive conditioned reflexes were markedly diminished, several completely disappeared. The inhibitory were disinhibited. Sometimes the ultraparadoxical phase set in, i.e., the positive stimulus was inactive and the inhibitory one differentiated from it gave a positive effect. During the experiment the dog was extremely excitable, sometimes breathing vigorously, very restless, sometimes showing marked excitatory weakness, reacting to the slightest fluctuation of the environment. Frequently he refused the customary feeding given after each positive conditioned stimulus. In a word, concerning the work with conditioned reflexes there was no doubt of an extreme, chaotic condition of the nervous activity. The same was manifest in the behaviour of the animal. Putting the dog on the stand and preparing it for the experiment, and also removing it was not easy; for the animal was intolerant and uncontrollable. When free he conducted himself very strangely; when lying on the floor he would turn on his side and crawl up to some one, which he never did before. The Diener who took him to and from the kennel reported that he had become mad.
Neither interruption of the experiments (rest) nor substitution of the inhibitory stimuli by the positive had a beneficial influence. His condition, instead of improving, continued for two months to get worse. Then we began the treatment. Thirty to forty minutes before each experiment we gave sodium bromide. On the second day there was a marked improvement and on the third day the dog was in all relations normal. The bromide was discontinued after the twelfth dose. For the next ten doses the animal remained completely well.
Now we pass to another experiment.
Together with the old positive conditioned reflexes in this dog, instead of the moderately loud noise, we applied for thirty seconds, like all the other positive conditioned reflexes, an exceedingly loud noise, even intolerable to our ears, and then we offered food. The animal gives a marked fear reaction, struggling from the stand and not taking food even at the cessation of the stimulus. However with the two following usual stimuli he reacts normally and takes the food. The application of the extraordinary stimulus was limited this time, but on another day the above described illness of the dog returned completely, and notwithstanding an interruption of ten to fifteen days and a regular rest of two days, his condition did not change for more than a month. Now we again give the same dose of bromide as at first; the improvement was marked on the third day, and on the sixth to seventh days the animal was altogether normal. Bromide was discontinued after ten doses. Here the experiments were interrupted by the vacation period.
It is not an exaggeration, it seems to me, to say that these experiments have a machine-like character. It is evident that they represent two pathological moments for the nervous activity: the excessive tension of the inhibitory process and the very strong external stimulus. Then a salutary factor in both cases was the production and strengthening of the inhibitory process just as at the basis of many other of our experiments bromides have been shown to have a direct relation to the inhibitory process, both producing and reinforcing it. Finally, a most important part of the therapy is the exact dosing corresponding to the precise type of nervous system.
Ivan Petrovitch Pavlov, Lectures on Conditioned Reflexes, Volume II: Conditioned Reflexes and Psychiatry, translated and edited by W. Horsley Gantt, Lawrence & Wishart Ltd., London 1941.