The Shibire Experiment

Doctor Josh Dubnau describes how he and his colleagues at Cold Spring Harbor Laboratory devised an experiment that dissociated the encoding and retrieval of memory in fruit flies.

It’s very difficult to distinguish between whether we’ve disrupted a memory in an animal’s brain, disrupted the storage/presence of a memory, or interfered with the ability of an animal to access that memory. In fruit flies we have a way of doing that by silencing a particular group of neurons in a reversible way. And an experiment that we did a number of years ago is to take a part of the brain of the fruit flies called the mushroom bodies – mushroom bodies are a known learning center in the flies. And what we did is we transiently, temporarily blocked those neurons from releasing their neurotransmitter. And when we did that we found that if you stop those neurons from firing, from releasing the neurotransmitter, while the animals were learning a lesson about a particular odor, and the lesson was that that odor predicted a nasty foot shock; so if you blocked those neurons from releasing transmitter while they learned, they could learn just fine. But if you block those neurons from communicating (from releasing neurotransmitter) while you later asked the animals to remember that experience, they couldn’t do it. What that told us is that the release of the neurotransmitter from the mushroom bodies is required to retrieve a memory, but not to lay down the association between the foot shock and the odor.