NEW YORK: Ever wondered how memory is made? Well, for the brain, remembering is like relieving, a new study has suggested.
Researchers have for the first time recorded individual brain cells in the act of summoning a memory, thus revealing where in the brain a specific experience is stored and how the brain is able to recreate it.
"In a way, reliving past experience in our memory is the resurrection of neuronal activity from the past," lead researcher Dr Itzhak Fried of California University said.
Dr Fried and colleagues at the Weizmann Institute of Science in Israel have based their findings on an analysis of the brains of 13 epilepsy patients being treated surgically at a medical centre in the US.
Surgeons had placed electrodes in the patients' brains to locate the origin of their seizures before surgical treatment -- standard procedure in such cases. Fried made use of the same electrodes to record neuron activity as memories were being formed.
In the study, the patients watched several video clips of short duration, including such things as landmarks and people, along with other clips of Jerry Seinfeld, Tom Cruise, 'Simpsons' character Homer Simpson and others.
As the patients watched, the researchers recorded the activity of many neurons in the hippocampus and a nearby region known the entorhinal cortex that responded strongly to individual clips.
A few minutes later, after performing an intervening task, the patients were asked to recall whatever clips came to mind.
The researchers found that the same neurons that had responded earlier to a specific clip fired strongly a second or two before the subject reported recalling that clip. These neurons did not fire, however, when other clips were recalled, the 'ScienceDaily' reported.
Ultimately, it was possible for the researchers to know which clip a patient was recalling before the patient announced it.
The study revealed that the single neurons that were recorded as they fired were not acting alone but were part of a much larger memory circuit of hundreds of thousands of cells caught in the act of responding to the clips.
"The study is significant because it confirms for the first time that spontaneous memories arise through the activity of the very same neurons that fired when the memory was first being made," Fried said.
7 months ago