R. HERNANDEZ-PEON AND H. BRUST-CARMONA 



395 



habituation in response to vestibular stimuli. In one case, habituation 

 persisted 4 years after the last experiment during which the subject was 

 rotated. 



By means of electromyographic recordings from the extra-ocular 

 muscles, we have confirmed in intact cats that repeated rotation leads to a 

 decrease of the number and amplitude of ocular movements. As shown in 



POST-ROTATORY NYSTAGMUS 

 IN A DECORTICATE CAT 



-('IVjVkAAA/'.MyiA/'^ 



FOLLOWING ACOUSTIC STIMULATION 



I — aMAAaAAAA/IAMAAA/\/ 



5— ajWaAa ^^-^aa^ 



[1000 >JV. 



Fig. I 



Electromyographic recordings of post-rotatory nystagnuis in 

 a decorticate cat. Recording was initiated immediately after 

 stopping rotation which lasted for 1 5 seconds. The rotations 

 were repeated every minute. The uppermost tracings represent 

 the initial control. The second shows the reduction of nystagmus 

 (habituation) after five trials. A startling acoustic stimulus was 

 applied and the nystagmus recorded after the ne.xt rotation 

 showed recovery (dishabituation) but it was reduced again after 

 five more trials (rehabituation). 



Fig. I, habituation of post-rotatory nystagmus was also present in cats 

 with bilateral removal of the neocortex, and usually the number of 

 rotational series needed to extinguish completely ocular movements was 

 less in them than in the intact cats. 



Since these experiments demonstrated that the neocortex is unnecessary 

 for habituation to vestibular stimuli, the role of the diencephalon and 



