47S 



BRAIN MECHANISMS AND LEARNINC; 

 EFFECT OF COND. INH. STIM. 



CONT. 



S-M CO. ■w Kw ^mi MM iiOiii m '^wi i»i » «ii V t>»i«>«> 



AFTER COND. INH. STIM. (BUZZ.) 





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AFTER COND. STIM. (T) 



Fk;. I 

 Contrasting cticcts of 'negative' and 'positive" stimuli. During training the following stimuli 

 were presented to this animal : (i) Absolute direct electrical excitation of . . . (effects not depicted 

 in this figure). (2) Conditioned or 'positive': a 1600 c.p.s. tone (currently reinforced by i)- (3) 

 Conditioned inhibitory or 'negative' : a buzzer (when tone was preceded by buzzer, the former 

 was never reinforced). EEG from sensory motor cortex. Upper line: control. Middle line: 

 repeateci application of buzzer ('negative' excitation) produced a condition that bchaviourally 

 and electrographically resembled sleep; two successive stages are shown (left, right). Lower 

 line: application of tone ('positive' excitation) provoked immediate arousal. Abbreviations: 

 BUZZ., Buzzer; COND., Conditioned; CONT., Control; INH.. Inhibitory; STIM.. 

 Stimulus; T., Tone. 



Calibration: 100 u v i sec. (unpublished figure from work by Scgundo, Roig and Soinmer- 

 Sniith, 1959). 



