Classical conditioning and retention in normal and mutantDrosophila melanogaster

Abstract

By changing the conditioned discrimination paradigm of Quinn et al. (1974) from an instrumental procedure to a classical (Pavlovian) one, we have demonstrated strong learning in wildtype flies. About 150 flies were sequestered in a closed chamber and trained by exposing them sequentially to two odors in air currents. Flies received twelve electric shock pulses in the presence of the first odor (CS+) but not in the presence of the second odor (CS-). To test for conditioned avoidance responses, flies were transported to a T-maze choice point, between converging currents of the two odors. Typically, 95% of trained flies avoided the shock-associated odor (CS+). Acquisition of learning was a function of the number of shock pulses received during CS+ presentation and was asymptotic within one training cycle. Conditioned avoidance increased with increasing shock intensity or odor concentration and was very resistant to extinction. Learning was best when CS+ presentations overlap shock (delay conditioning) and then decreased with increasing CS-US interstimulus intervals. Shocking flies immediately before CS+ presentation (backward conditioning) produced no learning. Nonassociative control procedures (CS Alone, US Alone and Explicitly Unpaired) produced slight decreases in avoidance responses, but these affected both odors equally and did not alter our associative learning index (A). Memory in wild-type flies decayed gradually over the first seven hours after training and still was present 24 h later. The mutants amnesiac, rutabaga and dunce showed appreciable learning acquisition, but their memories decayed very rapidly during the first 30 min. After this, the rates of decay slowed sharply; conditioned avoidance still was measureable at least three hours after training.

Specific requirement of NMDA receptors for long-term memory consolidation in Drosophila ellipsoid body

“…Olfactory associative learning was measured by training 2-3-day-old adult flies in a T-maze with a Pavlovian conditioning procedure 48 . Groups of about 100 flies received one or ten sessions of massed or spaced training during which they were exposed sequentially to one odor (conditioned stimulus, CS+; 3-octanol or 4-methyl-cyclohexanol) paired with electric shock and then to a second odor (CSÀ; 4-methyl-cyclohexanol or 3-octanol) without eletric shock.…”

Operant conditioning in invertebrates

“…Research on the genetically renowned fruit fly Drosophila (Figure 1a) has been revealing a steady flow of genes that are involved in olfactory classical conditioning for the past three decades [3][4][5][6][7][8][9][10][11]. Many of these genes affect the level of the second-messenger cAMP and are preferentially expressed in a prominent neuropil in the fly's brain, the mushroom bodies (Figure 1b; [12][13][14]).…”

Dissociation of visual associative and motor learning in Drosophila at the flight simulator

“…Behavioural and molecular genetic analyses of Drosophila mutants have been widely employed to study the olfactory classical conditioning from genetic to behavioural levels. It is now clear that in olfactory classical conditioning (Tully and Quinn, 1985) the CS-US association mostly occurs within mushroom bodies (MBs) (Dubnau et al, 2001;McGuire et al, 2001). With the operant conditioning paradigm, the MBs were demonstrated to be dispensable for the visual associative learning (Wolf et al, 1998) but were necessary for some cognition-like functions (Liu et al, 1999;Tang and Guo, 2001).…”