The Effect of Roentgen Rays on the Brain

THE study of the effect of roentgen exposure on the activity of the cerebral hemispheres was first undertaken by me over four years ago, i.e., in 1927. Even the first findings served to show that evidently my suppositions were confirmed. Due to roentgen exposure the conditioned reflexes in dogs after a fairly short period of time showed certain deviations from such reflexes as had been previously firmly established. These changes, as a rule, revealed a primary increase of the reflexes, followed by their more or less lasting decrease (see curves). Besides, a qualitative deviation from normal reflexes was observed. Thus, a stronger stimulus produced a weaker response as compared to that produced by a weaker stimulus, and so forth. The important findings I then obtained enabled me, in the Summer of 1928, to make a preliminary communication at the V All-union Congress of Roentgenologists and Radiologists and at the II International Congress of Radiologists in Stockholm. However, realizing the importance of the subject, I put off the publication of my paper until the findings reported in my preliminary communications had been confirmed by further experiments and investigations. Later, after a suitable laboratory, with a technically perfect chamber, had been equipped at the State Institute of Roentgenology and Radiology, the investigations were carried out along several different lines. The work was carried out in collaboration with Professor P. S. Kupalov, A. M. Ushakova, and Professor R. S. Lyman, of the United States of America. Histologic examination of the brain was performed in the case of some dogs in Munich by W. Scholz. Besides, studying the conditioned reflexes in adult dogs, the brains of which had been subjected to roentgen exposure, I also started to expose to roentgen rays the brains of pups in whom conditioned motor reflexes were subsequently established. When the pups became adult dogs they were provided with salivary fistulæ and their salivary responses were then studied. The peculiar conditions of a roentgen room were made familiar to the dogs at an early age; they were taught to lie motionless under the roentgen tube without being either anesthetized or fixed to the stand. This served to exclude the effect of such undesirable factors as an anesthetic or the sense of fear on the behavior of dogs. Our further investigations fully confirmed the findings I reported in my preliminary communication. Likewise, we were able to observe a number of most interesting phenomena concerning dogs which had been subjected to radiation at an early age. Thus, we observed in radiated pups a tendency to walk in circles for several months subsequent to exposure to the roentgen rays. The dogs mostly walked in circles clockwise. They showed considerable delay both in growth and weight, as well as in mental development. With time, this backwardness was more or less overcome, depending on the dosage applied.