Washington: Researchers have been able to discover how memory functions in a human brain. They have discovered how the brain's nervous system helps one learn and remember sights, sounds and smells that eventually make up long-term memory for the facts and events.

Neuroscientists at New York and Harvard varsities studied the activity of neurons in the brain's nervous system, and found how the brain signals the formation of new associative memories. The findings are said to be the strongest direct evidence till date as far as understanding the functioning of brain is concerned. And this is a critical first step in intervening in situations where memory function is impaired such as Alzheimer's disease.

The findings have appeared in "Science" publication in a paper entitled "Single Neurons in the Monkey Hippocampus and the Learning of New Associations."

The scientists examined the neural correlates of associative memory formation by using electrodes to monitor the electrical activity of individual neurons in the brains of monkeys performing an associative learning task. Each day the monkeys were shown complex images superimposed with four identical targets.

As the monkeys learnt through trial and error, which target location was associated with which reward, the scientists observed dramatic changes in the activity of some hippocampal neurons. They termed these as "changing cells". The changes in neural activity paralleled the animal's behavioural learning curve indicating that these neurons are involved in the initial formation of new associative memories.

One of the scientists said the activity in many such cells continued after the animal learnt the association, the research that these cells may participate in the eventual storage of the associations in long-term memory.

ANI