SMALL MINDS Using genetic manipulation and light beams scientists created a memory in a fly’s brain that made a tennis shoe smell something to avoid.
By NICHOLAS WADE
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 Miesenböck of the University of Oxford, leader of the team that has developed the new technique.
Psychologists study learning by running rats through mazes, but biologists want to learn the actual 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 Mr. 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, Dr. Miesenböck’s team has now managed to peer deep inside the black box of the fly’s learning system.