E. GRASTYAN 263 



ceased to elicit changes. I agree with Dr Jouvct that after decortication ot the 

 animal the extinction of the orientation reflex becomes very ditiicult. We made 

 exactly the same observation after extirpation ot both hippocampi. The animal 

 can still learn, but yon cannot extinguish its orientation reflex — it remains always 

 the orientation reflex which mediates the final act. 



BuSER. I wonder if Dr Grastyan could give us some more details about l^r 

 Eidelbcrg's experiments on coagulation of centre median. What was the behaviour 

 of those animals? My question is in connection with the observation made on one 

 animal with very large bilateral destruction of the medial thalamus (including 

 centre median): this animal would show strong orientation as well as startle 

 reactions. 



Grastyan. Dr Eidelberg's experiments were carried out on the rabbit. After 

 bilateral lesion of the centre median — the slow potentials irreversibly disappeared 

 euiirely from the hippocampus. In some cases after unilateral lesion it disappeared 

 on the same side. 



BusER. What about behaviour; 



Grastyan. He did not make any observations on behaviour. 



RosvoLD. It is comforting to hear of these electrical eliects because they help to 

 explain the findings that human memory is affected by hippocampal damage, and 

 that the monkey with hippocampal damage has dirticultv in solving problems 

 involving memory. 



