Scientists at UCLA (University of California, Los Angeles) and theWeizmann Institute of Science, Israel have discovered the process
through which memories are made and then recalled. These scientists have recorded that How individual brain cells calls up a memory?, thus revealing where in the brain a specific memory is stored and how the brain is able to recreate it.
Dr. ITZHAK FRIED
Dr. Itzhak Fried, Senior Study Suthor and a UCLA Professor of Neurosurgery with his colleagues recorded the activity of hundreds of individual neurons making memories in the brains of 13 epilepsy patients being treated surgically at UCLA Medical Center. Their research detail has been reported in current online edition of the Journal Science.
Surgeons at UCLA Medical Center placed electrodes in the patients' brains to locate the origin of their seizures before surgical treatment which is a standard procedure in such cases.Dr. Fried used same electrodes to record the neuron activity as memories were being formed.
During the experiment patients were shown 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 these clips, researchers recorded the activity of many neurons in the Hippocampus and a nearby region known the Entorhinal Cortex that responded strongly to individual clips.
Few minutes after watching these clips, the patients were asked to recall whatever clips came to mind. During this recalling process these patients were not prompted to recall any specific clips," but to use "free recall' which means, whatever popped into their heads.
At this point 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. By observing this researchers found that which clip a patient was recalling before the patient announced it.
During this experiment Dr. Fried noted 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.
This research is significant in the fact that 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. This link between reactivation of neurons in the Hippocampus and conscious recall of past experience has been suspected and theorized for sometime, but the study now provides direct evidence for this.
So we can say that, Reliving past experience in our memory is the resurrection of neuronal activity from the past.
The research was funded by the U.S. National Institute of Neurological Disorders and Stroke, as well as the Israel Science Foundation and the U.S.-Israel Binational Science Foundation.