Acquisition of a conditioned taste aversion becomes context dependent when it is learned after extinction

After the lecture on Thursday about Pavlov and his conditioning research, I found the conditioning and unconditioning stimuli quite interesting. According to our textbook, a conditioned stimuli is an originally neutral stimulus that after association with an unconditioned stimulus, triggers a conditioned response.  An unconditioned stimulus occurs naturally and automatically, and triggers a response. Research has shown that contexts play a small role in retrieval of simple conditioned stimulus-unconditioned stimulus relationships. From previous research, human and nonhuman animals share basic mechanisms of learning and memory. Therefore, basic learning and memory effects in animal learning are expected to be replicated in humans. Extinction is the conditioning phenomenon in which a previously learned response to a cue is reduced when the cue is presented in the absence of the previously paired aversive or appetitive stimulus.

The study I found tested 32 female rats that were about 70 days old. This study took place over 16 days.  Throughout the experiment the rats were kept on a water-deprivation schedule that included two 15-minute sessions of free access to fluid. In order to account for the context, two different sets of cages were used. Context A had the walls covered with red squared patterned paper and context B had the walls covered with dark green paper. Two flavors were used in this study to flavor the water. First, a solution of saccharin and another, a solution of salt. Both solutions were diluted in water.  Rats were exposed to both Contexts each day. Days 1-3 rats received water in the two sessions. On day three the rats were divided into 4 groups according to water consumption on the previous days. Days 4-5 all rats received distilled water in their daily sessions in the experimental contexts. On day 6, all rats received free access to the conditioned stimulus in Context A, the squared paper. An illness was induced, LiCl, to 2 of the 4 groups of rats. Immediately following the injection, the rats were left in Context A for 15 minutes. Rats still received distilled water in Context B during the other daily session. Day 7 was identical to days 4-5 with exception that the other two groups of rats received the LiCl injection after the water consumption in Context A. On day 8 rats received distilled water. Days 9-11 all rats received three sessions of condition stimulus X, which was the saccharin solution in Context A. Day 12 began the conditioning of stimulus Y, which is the salt solution. On this day all rats received access to flavor Y followed by an injection of LiCl. Day 13 all rats received distilled water, just like day 8. Days 14-16, all rats received free access to flavor Y in one of the two daily sessions while also received water in the alternate session for a total of three extinction trials. Two groups of rats received flavor Y in Context B while the other two groups of rats received flavor Y in context A. The reported experiment explored the influence of extinction of a flavor on context dependency of a different flavor that was then followed by the unconditioned stimulus. It could be expected that the purposeful effect of extinction on context processing may disappear when the number of extinction trials is increased.

Some results in the animal literature indicate that the effect of context change on extinction weakens when the level of extinction increases. In this experiment, I learned that the context specificity of an definite conditioned stimulus occurs after extinction in nonhuman animals. Under the present circumstances, extinction of a conditioned flavor makes conditioning of an alternate flavor context specific.

Rosas, J. M., & Callejas-Aguilera, J. E. (2007). Acquisition of a conditioned taste aversion becomes context dependent when it is learned after extinction. Quarterly Journal of Experimental Psychology, 60(1), 9-15. doi:10.1080/17470210600971519

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