Multiple-phase model of memory consolidation confirmed by behavioral and pharmacological analyses of operant conditioning in Drosophila.

Previous work on classical olfactory learning and memory in flies has suggested at least four distinct phases of memory consolidation. Similarly, our behavioral and pharmacological analyses also provided clear evidence for at least four pharmacologically distinct memory phases in flies after operant conditioning. Anesthesia-resistant memory (ARM) is present between about 20 and 120 min after training, and susceptible to disruption by the ATPase deactivating chemicals such as ouabain and ethacrynic acid (EA). Long-term memory (LTM) is activated at least 150 min after training, and can be disrupted by protein synthesis inhibitors such as cycloheximide (CXM). In addition, a very short-term memory (pre-STM) is demonstrated by feeding flies with potassium chloride (KCl), which has been shown to disrupt the short-term memory. These observations confirm our previous argument that memory formation in flies involves an intricate, multiple-phase pathway of consolidation.