358 



p. TEITELBAUM AND A. N. EPSTEIN 



intragastrically. They regulate their intragastric intake of a diluted liquid 

 diet normally and maintain their weight. Therefore, they no longer need the 

 powerful motivating stimulus provided by taste to demonstrate adequate 

 regulation of food intake. They have recovered sufficiently to regulate their 



EATS WEI 

 PftLATOBLE FOODS 



:^ ^ 



REGULPiTES FOOD 

 INTAKE e^ BODY W)T. ON 

 WET PALATABLE FOODS. 



^ 



EATS DP>V FOODS 





(if HVDRATED) L_^> 



DPvlNKS WATER 



Survives on drv 

 food and water 



Stage I 



AOIPSIA, 

 APHAGIA 



o 



stage H 



o 



siaqg nr 



ADlPSlA. 

 DEHVDRATIOhO- 

 APHAGIA 



Stage EZ 



RECOVERY 



VE5 



VES 



Fig. 8. Stages of recovery seen in the lateral hypothalamic syndrome. The 

 critical behavioural events are listed on the left. (From Teitelbaum and 



Epstein, 1962.) 



caloric intake without the motivation provided by a highly palatable taste. 

 But they still refuse to drink water. If offered only dry food and water, 

 even after they have regulated their intake of a liquid food perfectly well, 

 they refuse to drink, and become dehydrated. They therefore refuse to eat, 

 and once again will starve to death. This stage is one in which they do 

 not eat because they do not drink, and we have therefore called it the stage 

 of adipsia with secondary dehydration aphagia. Many animals after 

 lateral hypothalamic lesions show permanent adipsia. They have re- 

 covered the urge to eat but do not appear to possess true thirst. However 

 they can be induced to drink fluids merely by making them taste sweet. 

 They can be weaned gradually from the liquid diet by mixing it with more 

 and more 10 per cent sucrose. From this in turn, they can be weaned to a 

 0.5 per cent or a 0.2 per cent saccharine solution. They ingest this fluid 

 and therefore hydrate themselves sufficiently to eat dry food. At this 

 point, they are taking fluid solely on the basis of its sweet taste. They have 

 been tricked into hydrating themselves by off'ering them a sweet fluid, to 

 which they respond as though it were a food. This has been demonstrated 

 by showing that they increase their intake of saccharine solutions tremen- 

 dously when they are deprived of food but they do not ingest it when made 

 thirsty by complete deprivation of fluid or by dehydration with intraperi- 

 toneal hypertonic saline. Normal animals respond to saccharine either as a 



