Action of Gamma Radiation on Electrical 

 Brain Activity* 



Marcel Moxnier and P. Krupp 



University of Basel, Switzerland 



In the rabbit, the head was irradiated with a cobalt source producing 

 chiefly samma radiations. Various doses were applied : weak doses of 400 r, 

 in 7 animals; medium doses of 600 r. in 7 other animals: and strong doses 

 of 900 r. in 6 animals. The irradiation was effected under the following 

 conditions: intensity: 1.3325 and 1.1728 Mv: surface: 29.16 and 23.76 cm-; 

 focal distance: 30 and 20 cm: brass filter: 0.5 mm. 



We obser\ed and filmed the beha\ior of the animal before and after 

 irradiation. The efTects of oamma radiation on the electrical brain acti\ity 

 were analyzed using the stereota.xic method we dexeloped with Dr. Ganuloff 

 for research on the conscious rabbit ( Monnier and Ganglofl", 1961 i. 



A stereotaxic coordination system Fis. 1 i helps to locate precisely cortical 

 and subcortical structures, in which electrodes are introduced for stimulation 

 or recording purposes Fie 2 i . The electrical acti\ities of the cortex are 

 deri\ed by means of epidural siher electrodes screwed into the skull, whereas 

 subcortical structures are explored by means of platinum needle electrodes 

 implanted in the caudate nucleus, hippocampus dorsalis. thalamius medialis 

 and lateralis, and midbrain reticular formation. Attention is gi\-en not only 

 to the spontaneous brain acti\ity. but also to potentials evoked by electrical 

 stimulation of the midbrain reticular formation, medial and lateral thalamus, 

 and dorsal hippocampus. These structures are stimulated with needle elec- 

 trodes of the Hess type. The technique allows recording of the electrical 

 brain activity in the awakened restrained animal, as well as in the free 

 mo\ing animal Fia;. 3 ) . 



All derived electrical activities were recorded with a 16 channel Schwarzer 

 electroencephalograph and. for closer analysis, with a cathode ray oscillo- 

 scope. We analvzed onlv the acute effects of irradiation, the earliest and 

 latest obser\ations beini; made at 30 minutes and at 6 hours after radiation, 



* Supported by a grant of the Fonds National Suisse de la Recherche Scientifique. 

 with the technical collaboration of Dr. Meinardus, Prof. Zdansky, and S. Graber, 

 Uni\ersity of Basel. 



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