Olfactory Conditioning in C. elegans.
We have devised a new associative learning paradigm which uses the ability of C. elegans to track odors. An attractive odor (Diacetyl) is used as the conditioned stimulus (CS) while acetic acid (which is aversive) is used as the unconditioned stimulus (US). Non-food deprived worms are washed onto a fine wire filter and exposed to diacetyl followed by a brief exposure to acetic acid. After six rounds of conditioning, individual worms are tested for their tracking response to a small drop of the CS. A high proportion of naive worms show a tracking response to the CS. However, after conditioning a significant percentage of worms no longer track the CS suggesting that they no longer find it attractive. lrn-1 and lrn-2 mutants, which were previously isolated using a Na+/Cl- + E. coli learning paradigm and has subsequently failed to learn other associative paradigms are also impaired in this task.
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