Scientists have detected evidence of individual brain cells signalling the formation of new memories.
By Dr David Whitehouse
BBC News Online science editor
Neurons that scientists call "changing cells" in the hippocampus - sometimes called the brain's memory hub - give off specific types of signals as a monkey commits tasks to memory.
New memories: The research team traced the location where they are made
It is well known that new associative memories - such as learning the name of a new acquaintance - require the involvement of the hippocampus.
But this is the first time that researchers have pinpointed the details of memory formation at the neural level.
"When hippocampal cells undergo these striking changes in neuronal activity, it's like watching a new memory being born," says Wendy Suzuki, of New York University, US.
The researchers monitored the activity of individual neurons in the hippocampus as two monkeys formed new associative memories while playing a computer game.
Among 89 neurons that responded to the scenes in the computer game, it was discovered that 25 changing cells were intimately involved in learning as their activity increased and decreased during the learning process.
It appears that the activity of the changing cells is coordinated in a particular way when new memories are laid down.
Some of the changing cells showed sustained activity after the trials were over, while others returned to their normal levels.
Researchers think that the "sustained changing cells" may also be involved in the formation of long-term memory.