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As part of a project to understand how the brain learns, biologists have written memories into the cells of a fruitfly’s brain, making it think it had a terrible experience.

 

The memory trace was written by shining light into the fly’s brain and activating a special class of cells involved in learning how to avoid an electric shock.

The goal of the research is not to give flies nightmares but rather to understand how learning in general works, from flies to people. “In the case of the fly, where we have a numerically rather simple nervous system that does something rather complex, I think we have a chance to break open the black box and understand it,” said Gero Miesenbock of Oxford University, leader of the team that developed the new technique.

Psychologists study learning by running rats through mazes, but biologists want to learn the mechanics of how a memory trace is laid down in a nerve cell or neuron. So they need an organism whose genes can be easily manipulated.

In the early days of molecular biology, when others were working on DNA, the biologist Seymour Benzer decided to dissect behavior by studying the fruitfly. His student Chip Quinn discovered in the early 1970s that fruitflies, surprisingly, could learn. If exposed to a chemical odor and at the same time given an electric jolt big enough to kill a person, the fruitflies associated the two and would in the future avoid the odor.

Of the two chemicals that Quinn picked, one smelled like licorice and the other “a lot like tennis shoes in July”, according to Jonathan Weiner, author of ‘Time, Love, Memory’, an entrancing history of Benzer’s work. Biologists ever since have used the same system to train fruitflies.

With the aid of the licorice and tennis shoe odors, Miesenbick’s team has now managed to peer deep inside the black box of the fly’s learning system. His goal is to dissect the neural circuitry through which the fly associates a particular odor with electric shocks, so he began by looking at a class of neurons that generate the chemical messenger dopamine.

In our brain, dopamine signals pleasure and reward but in flies it does the exact opposite: it is the messenger of fear and aversion. The fly has some 200 dopamine-producing neurons, and these must be involved to help the fly associate fragrance of tennis shoe with a really bad scene.

Via Times of India

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