What happens to the brain when it replays memories? A study from the National Institutes of Health (NIH) uncovered that firing patterns of the cells that emerged when patients discovered a word pair were replayed fractions of a second before they recalled the pair.
The study was a part of an NIH Clinical Center trial for patients with drug-resistant epilepsy and whose seizures are uncurable.
To determine what happens to the brain when it replays memories, the researchers examined the electrical activity of individual brain cells of epilepsy patients when they took memory tests.
"Memory plays a crucial role in our lives. Just as musical notes are recorded as grooves on a record, it appears that our brains store memories in neural firing patterns that can be replayed over and over again," said Kareem Zaghloul, M.D., Ph.D., senior author of the study and a neurosurgeon-researcher at the NIH's National Institute of Neurological Disorders and Stroke (NINDS).
Their team investigated the firing patterns of individual neurons found in the anterior temporal lobe, which is considered a brain language center. The participants sat in front of a screen and were taught word pairs such as "cake" and "fox."
Their findings showed that unique firing patterns of individual neurons were linked with learning each new word pattern. Meanwhile, when a patient came across one of the words, like "cake," a similar firing pattern was replayed milliseconds before the patient remembered the paired word "fox."
"These results suggest that our brains may use distinct sequences of neural spiking activity to store memories and then replay them when we remember a past experience," said Dr. Zaghloul.
"We thought that if we looked carefully at the data we had been collecting from patients we might be able to find a link between memory and neuronal firing patterns in humans that is similar to that seen in rodents," said Alex Vaz, the study's leader and a bioengineer who specializes in deciphering the meaning of electrical signals generated by the body.
