ACTION OF GAMMA RADIATION ON ELECTRICAL BRAIN ACTIVITY 615 



Action of Gamma Radiation on Electrically Evoked Activities 



Electrographic arousal reactions induced by an acoustic stimulus (click), 

 or by electrical stimulation of the midbrain reticular system or posteroventral 

 hypothalamus at high frecjuency (150 cps ) are slightly enhanced by weak 

 irradiations (400 r and 600 r j , but slightly depressed by stronger doses 

 (900 rj (Fig. 7). 



Threshold 



Voriation 



VOLT 



0.1 



+ aosH 







— ao5 



0.1 - 



ai5- 



AROUSAL REACTIONS 



Stimulation of midbrain reticul syst 150/sec. 



0,1 - 



+ 0.05- 







— ao5- 



0.1 - 

 0.15 

 0.2 -i 



\ 

 \ 



•900r 

 AOOr 

 600r 



I I I 1 1 1 



1 2 3 A 6 hours 



1 Irradiation 

 ' Cobalt 60 



Stimulation of hypothalamus post lat 150/sec^ 



-900r 



400 r 



\ 



.-600r 



6 hour; 



Fig. 7. Action of various gamma irradiations on the threshold of the arousal reac- 

 tions evoked by stimulation (150 cps) of the midbrain reticular system (above) and 

 of the posteroventral hypothalamus (below). 



