442 BRAIN MECHANISMS AND LEARNING 



In. some conditions they obtained a reduction of the negative component 

 whereas the positive potential remained conipletely unaffected. Gauthier, 

 Parma and Zanchetti (1956) observed that the primary response ehcited by 

 peripheral stimulation is defniitcly decreased during cortical arousal but 

 they did not give any detail regarding the influence upon the positive and 

 negative component ot the response. Appclberg, Kitchell and Landgren 

 (1959) studying the reticular influence upon thalamic and cortical poten- 

 tials evoked by electrical stimulation of the cat's tongue observed a con- 

 siderable reduction of both components of the primary response. They 

 did not mention any difference in the behaviour of the positive and 

 negative components. This fact could be attributed to the different 

 parameters of stimulation of the reticular formation used. Changes in two 

 components of the primary response evoked by tactile stimulation were 

 observed by Narikashvili (1957) related with the recruiting response: 

 when the primary response preceded or coincided with the rising slope of 

 a recruiting response potential, the negative spike of the evoked potential 

 was increased (the positive was blocked) ; if the primary response arose 

 when the potential of the recruiting response was fully developed, then its 

 positive component was increased and the negative was blocked. He 

 observed also that the EEG desynchronization had less effect on the primary 

 response: it suppressed the negative component or had no effect. 



Buser and Borcnstein (1957) working in cats anaesthetized with chlora- 

 lose report the existence of induced potentials in association cortex areas by 

 single stimulation of the reticular formation and its inhibitory effects on 

 the secondary response. The conflicting results obtained by different 

 investigators regarding potentials evoked in the cerebral cortex by stimu- 

 lation of the reticular formation could be attributed to the multisynaptic 

 interneuronal organization of this system that makes it more susceptible 

 to anaesthetic blockade, but this susceptibility varies with the different 

 anaesthetics. Contrary to Buser and Borenstein, response to reticular 

 stimulation in primary areas and inhibition of the primary response was 

 obtained in the present work. 



French, Verzeano and Magoun (1953) reported a different sensitivity of 

 the waves of the primary response to anaesthetics. They observed that the 

 initial event of the primary response was never diminished by anaesthesia 

 (ether or nembutal) ; on the contrary it was sometimes augmented, while 

 the second cortical deflection usually diminished in amplitude and Anally 

 disappeared. Feldberg, Malcolm and Smith (1957) observed that the 

 intraventricular injection of small doses of tubocurarine in cats under 

 chloralose caused definite changes in the primary response evoked by 



