GENERAL DISCUSSION 623 



hippocampus activation produced a stuporous state in our animals resembling 

 psychomotor stupor. The rabbit does not react any more during the critical 

 discharge. Concerning Dr. Sharp's question, we use two stimulation techniques. 

 One — high frequency of 150 per second — is used just for producing the classical 

 arousing reaction. But threshold measurements of evoked potentials are done with 

 single shock or low frequency stimulation (three per second). This is the low 

 frequency stimulation with which we analyze the responses of all thalamocortical 

 projections — specific and unspecific, hippocampocortical and reticulocortical projec- 

 tions. They all were analyzed at this low frequency stimulation. 



Herbert Locksley (State University of Iowa, Iowa City, Iowa): Dr. Brown 

 made the interesting observation of postirradiation increase in spinal pressure in 

 burros. Were these Nevada or Godiva irradiated burros? What was the average 

 dose level? What was the time relationship of his measurements to irradiation? 



Daniel G. Brown (University of Tennessee, Oak Ridge, Tennessee): These 

 cerebrospinal fluid pressure measurements were made on burros that received 

 485 r to the head. We made no spinal fluid pressure measurements on any of the 

 other burros. This was from the head irradiation experiment. The animals were in 

 a morbid state, that is, they were in a state of coma and were near death. We 

 measured the cerebrospinal fluid pressure at about 28 hours after irradiation and 

 they died at about 30 hours. 



Edgar L. Gasteiger (University of Rochester, Rochester, New York): I would 

 like to ask Dr. Monnier, or anyone else using his implanted electrode technique, 

 whether the effects might result from secondary emissions at the electrodes? When 

 you irradiate a preparation with implanted metallic electrodes might you have 

 localized effects due to secondary emissions from the electrodes? 



M. Monnier: The histologic controls showed a slight increase in the trace of 

 the electrodes. However, it is not possible that the chief effects reported by us 

 result from secondary emissions at the electrode. We have about 20 electrodes in 

 the brain, and only some of them showed the specific changes described. That is 

 why we are not too pessimistic about the role of the implanted electrodes. 



C. D. Clemente (University of California, Los Angeles, California): Professor 

 Grashchenkov, there are a number of investigators in the United States who, too, 

 believe vegetative centers in the central nervous system may be more radiosensitive 

 than in other areas. Do the Russian investigators believe that the effects that they 

 have shown with extremely low doses on brain areas are a result of humoral agents; 

 and, if so, is this humoral agent epinephrine? 



N. I. Graschenkov (Moscow, U . S. S. R.): We have many contradictory pub- 

 lications about the part of the brain which is most sensitive to irradiation. I 

 believe the hypothalamic area is more sensitive because I dealt with this area for 

 many years with my collaborators and find much evidence to indicate that this part 

 of the brain plays a very important role in many processes and is sensitive to ionizing 

 radiation. But some Russian investigators, as I review the literature, believe that 

 the cortex plays a very important role, and some show that even the cerebellum 

 plays a very important role in ionizing radiation. Of course, we have different 

 opinions about it, but most publications are concerned with hypothalamic areas 

 or encephalitic areas which are more sensitive to ionizing radiations as most 

 people show it with EEG methods and neurohumoral methods. 



