Washington, Oct 16 Oxford scientists have succeeded in directly manipulating the activity of individual neurons to give flies memories of a bad experience-something they never really had.

"Flies have the ability to learn, but the circuits that instruct memory formation were unknown. We were able to pin the essential component down to 12 cells. It's really remarkable resolution," said Gero Miesenbock of the University of Oxford.

The dozen cells are sufficient to manage what is a difficult cognitive problem- learning to associate a particular odour with something bad, like an electric shock.

This means that these cells create memories that the fly then uses to avoid that odour.

To pinpoint the exact neurons responsible for this memory among thousands in the fly brain, the researchers used a clever technique they developed, called optogenetics, in which a simple flash of light is used to release caged-molecules present in selective neurons that then stimulate the activity of those neurons.

Miesenbock said that an analogous situation is if you wanted to send a message only to certain inhabitants of a city, you would give those you wanted to reach a radio tuned to the right frequency and send the message publicly, over the airwaves.

He said that his team made some educated guesses about the parts of the brain that would be important for the flies' learning task.

From there, they were able to narrow it down through experimentation to the 12-neuron brain circuit.

Remarkably, stimulating just these neurons gives the flies a memory of an unpleasant event that never occurred.

"We like to take seemingly lofty psychological phenomena and reduce them to mechanics, to see for example how the intelligence needed to adapt to a changing environment can be reduced to physical interactions between cells and molecules.The question is: how do you get intelligence from parts that are unintelligent?" he said.

Using their approach to "write directly to memory," scientists can now obtain a level of evidence about brain function that was impossible before, said Miesenbock.

The study has been published in the latest issue of the journal Cell, a Cell Press publication. (ANI)