Taste Aversion after Ingestion of Lithium Chloride: An Associative Analysis

Abstract

In five experiments with rats we examined the aversion established by consumption of a solution of lithium chloride (LiCl). Experiment 1 showed that consumption of LiCl established an aversion to saline (NaCl). Experiment 2 showed that the size of the aversion was reduced in rats given pre-exposure to saline (a latent inhibition effect). Experiment 3 showed that experience of a sucrose-saline compound prior to consumption of LiCl generated an aversion to sucrose (a sensory preconditioning effect). Experiments 4 and 5 examined the effects produced by consumption of a sucrose-LiCl compound and demonstrated reciprocal overshadowing between the two tastes. These results confirm that consumption of LiCl establishes an aversion to the taste of this substance. Their implications for the use of orally consumed LiCl as a technique for the control of predatory behaviour are discussed.Studies of flavour aversion learning have made much use of lithium chloride (LiCl) as the unconditioned stimulus (US), usually in the form of an intraperitoneal injection and usually with the intention of establishing an aversion to some arbitrarily chosen flavour, presented prior to the injection. It has been noted (e.g., Nachman, 1963) that most toxic substances have unpleasant tastes, but that LiCl appears to be one of the exceptions to this rule. Nachman reported that thirsty rats given access to a 0.12 M solution of LiCl drank it readily, at least for the first 5 min of its presentation, during which period they drank about 8 ml. Thereafter the rate of drinking declined, and when tested 3 days later the rats refused to drink LiCl, although they readily drank plain water presented in the same way. Similar results have been reported by Simbayi (1987, Experiments 1 and 4). Nachman suggested that this effect was the consequence of an associative learning process in which the taste of the LiCl had become associated with the aversive consequences (i.e., the nausea) induced by its initial consumption. In support of this conclusion he reported that the rats also refused to drink a sodium chloride (NaCl) solution, which appears (to humans) to have the same (salty) taste as LiCl. Furthermore, Requests for reprints should be sent to G. Hall,

The US-Preexposure Effect in Lithium-Induced Flavor-Aversion Conditioning Is a Consequence of Blocking by Injection Cues.

“…No data were recorded during the preexposure phase. As we anticipated, on the basis of the results of Loy and Hall (2002), the rats (in the LI-LO and SI-LO groups) given access to the LiCl solution in Conditioning trial 1 drank it as readily as those (in the SI-SO group) given saline. Group mean scores were 3.8 ml and 4.0 ml for the LI-LO and SI-LO groups and 3.9 ml for the SI-SO group.…”

“…The SI-SO (SO: saline taken orally) group also received injections of saline during preexposure but drank NaCl rather than LiCl in the next phase. On the basis of the results of Loy and Hall (2002), subjects in the SI-LO group can be expected to show an aversion to the NaCl solution on test and thus drink less than subjects in the SI-SO group. Subjects in the LI-LO group might also be expected to show an aversion; the question of interest was the extent to which their preexposure treatment might attenuate this aversion.…”

“…In Experiment 1b, we attempted to eliminate this problem by counterbalancing the flavors used as the CS in the two cases. Loy and Hall (2002) have shown that rats that drink a solution of LiCl presented in compound with another flavor (sucrose, in their experiments) will develop an aversion to the other flavor. We made use of this technique in the present experiment.…”

“…Loy and Hall (2002) investigated this effect and demonstrated it to be a consequence of associative learning in which the nausea induced by consuming the LiCl solution establishes an aversion to its salty taste. (The effect was exactly comparable in magnitude with the aversion produced by giving an intraperitioneal injection of an equivalent quantity of LiCl to rats that had just consumed a saline solution.)…”

Interactions between retroactive-interference and context-mediated treatments that impair Pavlovian conditioned responding

“…In certain compound conditioning situations, CS preexposure actually attenuates the overshadowing effect that otherwise occurs as a result of compound training (Blaisdell, Bristol, Gunther, & Miller, 1998;Loy & Hall, 2002; but see Nakajima, Ka, & Imada, 1999;Nakajima & Nagaishi, 2005). In a conditioned suppression preparation with rat subjects, Blaisdell et al observed that preexposure to a CS (X) before reinforcing it in compound with a more salient CS (A) results in conditioned responding to X that is stronger than in a situation in which X is not preexposed prior to compound training.…”