ROBERT GALAMBOS 24 1 



mciit, or both. Docs a diftcrcncc in this complex event ever arise when the stiniukis 

 is changed, say from chck to hghtr 



Galambos. Again, we do not have the information for answering this question 

 precisely. The evoked response seems to be identical in many brain loci with 

 different stimuli, but in other places this is not so. One of our current problems is 

 to obtain just the data required to answer the question Dr Olds asks. 



HeknAndez-Peon. I would like to ask two brief questions — 1 noticed that 

 during anaesthesia there was an enhancement of one of the waves of the auditory 

 cortical potentials. I would like to know what is the interpretation ot this fact. 

 The other question is: where was the puff^ of air applied, because probably its 

 localization is of some importance in conditioning. For example, it it is applied to 

 the eye, the response is probably not extinguished or habituated. But we have 

 observed at the spinal V sensory nucleus that the potential evoked by a puff oi air 

 is decreased with repetition of the stimulus — and the habituation disappears by 

 giving anaesthesia. We also found that the pinna reflex evoked by giving repetitive 

 puffs of air disappears, but if we anaesthetize the cat the pinna reflex returns and is 

 not habituated under anaesthesia. 



Galambos. I had not considered the possibility that the exact region to which the 

 air puff reinforcement was delivered might make much difference. We have simply 

 blown the air into the animal's face. As to your question ot whether the evoked 

 response amplitude increases with anaesthesia, the answer is a somewhat qualified 

 yes. In the awake animal two electrical events are identifiable in the first 20 or 30 

 msec, of the cortical response to a click. One of these disappears with anaesthesia. 

 Since the two sum algebraically, removal of one allows the other — the well-known 

 'evoked response' — to stand alone, and it often seems then to have grown in size. 



Segundo. So far work on electrographic aspects of conditioning has analysed 

 changes that occur in the direct response to the indifferent and later conditioned 

 stimulus (Anokhin, 1958; Fessard and Ciastaut, 1954)- It seems opportune to 

 mention that, as a consequence ot training, the conditioned signal also became 

 capable of modifying the response to the absolute stimulus (in somatic sensory 

 cortex and perhaps mesencephalic reticular formation). Namely, the potential 

 evoked by a painful stimulus is larger when preceded by its conditioned signal than 

 when not preceded by it : in terms of human experience, it is larger when 'expected' 

 than when 'unexpected'. (Segundo and Sommer-Smith; Galeano and Roig, 1959). 



Finally, I would like to ask the interpretation for the short latency of visual 

 cortical responses to clicks. And it shapes of cortical and sub-cortical responses are 

 similar to shapes encountered in primary sensory cortex? 



Galambos. We are presently closely comparing cortical and subcortical records 

 for similarities and differences in their morphology and duration. Published data 

 confirm our own impression that such records show remarkable similarities 

 throughout a period ot 0.5 to i.o seconds following the conditioned stimulus. If 

 this should turn out to be correct, some new unexplained phenomenon existing in 

 large parts of the brain ot the conditioned animal would have to be assumed. 

 Such a phenomenon would certainly be worth careful stud)-. 



fUJ 







