Forgotten memories may be recoverable

New Scientist : In experiments with mice, researchers at MIT have shown that once something is learned it is never completely forgotten. Susumu Tonegawa and colleagues propose that memory involves the strengthening of synapses between neurons in the brain. To understand the process better, the researchers genetically engineered a group of mice to have neurons with extra genes—one gene produced red proteins when the neuron fired as a memory formed, and another gene caused the neuron to fire when illuminated by blue light. The mice were then given mild electric shocks to make them fear their cage, and the researchers noted which neurons emitted red proteins. To get the mice to forget their fear, the researchers administered a drug that blocked the strengthening of the neuronal connections. They then exposed those same neurons to blue light, which caused them to reactivate, and the mice were once again afraid of the cage. On the basis of their research, the scientists say that if the brain tissue is not damaged, it may be possible to restore the memories of people who are in the early stages of Alzheimer’s disease or have amnesia.