TASTE STIMULATION AND PxREFERENCE BEHAVIOR 267 



salivation, lethargy, anorexia, weight loss, muscular weakness, and death. 

 Lithium chloride was, for a while, marketed as a salt flavoring substitute 

 for persons on a low sodium diet until several cases of severe poisoning 

 were reported. In rats, the toxic after-effects apparently occur rapidly 

 since the rats stopped drinking during a 10-min period and soon became 

 lethargic and extremely inactive so that they lay flat on the floor of the 

 cage. 



Beidler (1953) and Fishman (1957) showed that Li and Na produced 

 very similar amounts of activity in the chorda tympani and that in single 

 fiber studies the discharge produced by Na was similar to that by Li. 

 Thus, it would appear that the taste of the two salts is highly similar and 

 leads to acceptance of either in short tests but rejection of Li after the 

 post-ingestive toxicity takes effe:t. Nachman also showed that the learned 

 aversion to Li generalizes most to NaCl, next to NH4CI, and least to 

 KCl, which follows the order of magnitude of size of chorda tympani 

 response. Erickson (1962) has recently demonstrated that rates of dis- 

 charge of single units in rat chorda tympani for KCl and NH4CI were 

 highly correlated, whereas no systematic relation held between these two 

 salts and NaCl discharges. Similarity of chorda tympani patterning 

 presumably signifies similarity of taste. These results are in accord with 

 Nachman's generalization data showing that rats can readily discriminate 

 the taste of either NH4CI or KCl from that of LiCl and NaCl, while they 

 apparently have great dilficulty in discriminating NaCl from LiCl. 



Two points bear emphasis in these experiments. First is the immediacy 

 of the enhanced preference for Ijthium and sodium in the initial post- 

 adrenalectomy tests in animals that have never been exposed to salt 

 solution prior to the test. This implies that there is an immediate effect 

 of need state upon the taste of salt, which also generalizes depending on 

 the degree of similarity to the taste of sodium chloride. Secondly, the 

 learned aversion to lithium persists for many months unless extinction 

 training is used. This shows the importance of a single post-ingestive 

 effect on changing the value of a taste stimulus. The prolonged enhanced 

 preference for salt after dialysis described above also leads to a similar 

 conclusion. These and other studies point to two aspects of taste prefer- 

 ence in states of need that have often been treated as antithetical, e.g. the 

 direct operation of taste factors versus the delayed operation of post- 

 ingestive metabolic consequences. Both can be shown to be important 

 and both, presumably, can interact to varying degrees under different 

 conditions. 



Two recent studies have emphasized the role of water metabolism and 

 hydration in the preference-aversion function for salt solutions in the non- 

 deprived animal. Deutsch and Jones (1960) found that mildly thirsty 

 rats learned to run to the arm of a T-maze that contained water, rather 



