Effects of pre-exposure and post-exposure of the context in habituation of the retraction response in earthworms (Lumbricidae).

The context specificity of habituation has been demonstrated in earthworms. After the habituation of the retraction response to a light, a recovery of the response was observed when subjects are re-habituated in a different context. Some theories assume that an association between the context and the unconditioned stimulus could underlie this result. A series of experiments were conducted in order to test this issue. We assessed the potential disruptive effects of post-exposure (extinction effect) and pre-exposure of the context (latent inhibition effect) on the establishment of a context-US association. A recovery of response during subsequent rehabituation test was expected. The results of Experiment 1 showed that the extinction was effective, the post-exposure of the context after habituation produced a recovery of the retraction response. This result was replicated in Experiment 2 where the post-exposure condition was compared with a pre-exposure one. However, the pre-exposure to the context did not result in a recovery of the response in the rehabituation test, but also produced a general decrement on the response during the habituation training, that it has been interpreted as decrement in context's salience. In summary, these results suggest the involvement of associative and nonassociative processes in habituation learning.

Contextual specificity of habituation in earthworms.

This article reports the context specificity of habituation in earthworms (Lumbricidae family). Using earthworms as subjects-which are typically sensitive to odors-the present study sought to evaluate the context specificity of habituation by giving subjects repeated exposures to a bright light in one odorous context, after which they were presented again with the same stimulus in a different context. The recovery of responding in this second context was higher in the group where the odor of this context was different, in comparison with a control group for which the context was the same. To provide further support for these findings, a second experiment was run using a within-subject design where all subjects were trained in both of the conditions. In this case, in addition to the light, vibration was used as a second stimulus. The subjects again displayed a higher increase in responding in the condition where the context was different (in odor) in comparison with the case in which the context was the same, thus replicating the results obtained in the first experiment. We discuss the implications of these results in the light of current data and learning theories. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Classical conditioning in earthworms employing an odorous conditioned stimulus.

The study of associative learning in invertebrates has become an essential tool for exploring their cognitive abilities and for studying the biological bases of learning and memory. In this experiment with earthworms, we paired a rose odour conditioned stimulus (CS) with a bright light unconditioned stimulus (US). After these pairings, the head retraction response - which is initially elicited by the bright light - is eventually evoked by the rose odour. This is the first demonstration of classical conditioning of an odour in earthworms (vibrations are usually employed as CSs), using a procedure that enables us to rule out an explanation in terms of pseudoconditioning.