I4o BRAIN MECHANISMS AND LEARNING 



occurred and, under the latter conditions, one should doubt whether wakefulness 

 derived from stimulation itself or from proprioceptive 'feed back' resulting from 

 clonic movements. The same 'indifference' was shown by the visual area: when the 

 animal was awake, excitation ^vith few volts produced investigation movements 

 directed towards the contralateral field; when the animal was asleep, stimulation of 

 up to 80 volts produced no effect. A different result occurred when excitation was 

 applied to temporal pole, cingular cortex or hippocampus: with low voltages, 

 animals were immediately aroused, both behaviourally and electroencephalo- 

 graphically (Scgundo, Arana and French, 1955). Therefore, and as far as we can 

 infer irom the influence of animal brain stimulation upon sleeping state or tendency 

 to excite itself, certain areas are 'indifferent' and others are not. 



Dr Doty mentioned that stimulation ot subcortical structures may be condi- 

 tioned, hi our laboratory, brief tones have been reinforced by direct excitation of 

 mesencephalic reticular formation, centre median, basolateral amygdala or head of 

 caudate nucleus and learned responses to tones have eventually appeared, hi some 

 cases (centre median, mesencephalic reticular formation, certain amygdaloid or 

 caudate placements) conditioned effects were practically identical to the absolute 

 responses. In other cases, responses from different pomts in caudate or amygdala, 

 could not be conditioned //; Mo; some of their components, however, could and 

 coiiset]uently conditioned responses were similar to a part of the absolute response, 

 hi a third group o( animals (also caudate or amygdala) the conditioned reaction, 

 though consistent, was completely different to the asbolutc effect. This variable 

 relationship has been found in other types of conditioning and, therefore, though 

 difficult to interpret here, is not altogether surprising (Hilgard and Marqtiis, 1940). 



To summarize we can say that stimulation effects of certain areas of the brain can 

 be conditioned. The latter term seems justified in the sense that the process has 

 many features (technique, effects, inhibitions) of classical conditioning. These 

 studies may help to understand the physiology of learning and that of tested nuclei 

 (Roig, Segundo, Sommer-Smith and Galeano, 1959; Seguiido, Roig and Somnier- 

 Smith, 1959). 



Chow, hi your monkey work, do you worrv about whether vour stimulus 

 would activate the pain sensation in your animal f 



Doty. We are very much aware that the factor of meningeal stimulation must 

 be considered. Dr Rutledge and I have shown that stimulation of the dura mater of 

 the saggital sinus in the cat can serve as a conditional stimulus and is undoubtedly 

 also a nocuous stimulation. However, I feel satisfied that, as outlined in the text, 

 this factor can be detected by the self-stmiulation procedure employed and was 

 present only as stated, hi addition, Dr Girugea has established these responses in 

 dogs after destruction of the Gasseriaii ganglion. 



Hernandez-Peon. The conditioned response obtained by Dr Doty using cortical 

 stimuli as conditioned and unconditioned stimuli provides a method for testing 

 defniitely whether there might be some cortico-cortical connections in some cases 

 of conditioning. And I wonder whether he has done transcortical cutting isolating 

 the respective cortical areas and testing whether these conditioned responses persist 

 after the transection or not. 



Doty. I think the experiments of Girugea and his colleagues showing these 

 conditional reffexes to be established after callosal section when the conditional 

 stimulus and unconditioned stimulus are in different hemispheres, indicate that a 



