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If you fall off your bicycle, you may end the experience with movie-like memories: wind in your hair, pebbles on the road, and then pain.
This is the so-called episodic memory. Now, researchers have discovered cells in the human brain that can make this kind of memory possible. Proceedings of the National Academy of Sciences.
These units are called time units, and they put some kind of time stamp on the memory when they are formed. This allows us to recall the sequence of events or experiences in the correct order.
Dr. Bradley Lega said: “By letting time units create this index across time, you can put everything together in a meaningful way.” The senior author of this study is also a neurosurgeon at the University of Texas Southwestern Medical Center in Dallas.
Time cells were discovered in rodents decades ago. But this new research is crucial because “the ultimate arbiter is always the human brain,” said Dr. György Buzsáki, a professor of neuroscience at Biggs at New York University. Buzsáki is not the author of the study, but he did edit the manuscript.
Lega and his team discovered time cells by studying the brains of 27 people waiting for severe epilepsy surgery. As part of the preoperative preparation, these patients place electrodes in the hippocampus and another area of the brain, which involve navigation, memory, and time perception.
In the experiment, patients studied a sequence of 12 or 15 words that appeared on the laptop screen in about 30 seconds. Then, after a short break, they were asked to recall the words they saw.
At the same time, researchers are measuring the activity of individual brain cells. They found a small number of words, and each word sequence would be triggered at a specific time.
Legar said: “The time unit we found is marking discrete time periods within a window of about 30 seconds.”
He said these timestamps seem to help people recall the time and order in which they saw each word. When we want an experience like falling down on a bicycle, the brain may use the same method.
Buzsáki said these results help explain why people with damaged hippocampus may experience strange memory problems.
He said that in an experiment, scientists compared the memories of a group of people who had just finished a trip to the University of California, San Diego-the trip included several performances.
All participants remembered most of the things they did, including locking the bike and drinking a drink from the water dispenser.
However, people with damaged hippocampus cannot handle these incidents properly. Buzsáki said: “These sequences disappear completely and absolutely in patients with hippocampal lesions.”
This new study shows that this is because their brains do not have time units, which will allow them to recreate the entire journey in their minds.
But even though time units are essential for creating sequences, Buzsáki says they really don’t look like clocks, which operate at a steady speed. Instead, the ticking of the time unit continuously speeds up or slows down, depending on factors such as emotions.
Buza Saki said: “When you have to wait for the election, every day is a long day.” “When we ask when the COVID is over, it is the same. It is very, very slow. But when you have a good time Time, time flies quickly.”