For each event, the brain prepares two tracks: one for immediate re-enactments, and one for the long term. The discovery rewrites the best known theories on the archiving of the experiences we live.
How do you go from a lived event to a lasting memory of it? An important American and Japanese experiment rewrites what was previously known about the consolidation of human memories.
For each episode lived, the brain creates two tracks: one destined for the „here and now“, and one made to last over time. The second remains silent for some time, but exists immediately: a discovery that overturns the belief, accepted by many, that all memories are at first „short term“, and over time are converted into stable traces.
A group of scientists from the Riken-MIT Center for Neural Circuit Genetics has shown that this does not work by manipulating some scary memories in mice with the help of light rays. The animals suffered a weak electrical discharge in a particular room; after that, the researchers observed if and when the memory of the trauma suffered came back to the surface by itself, and alternatively tried to reactivate it by modulating the activity of the neurons involved with light.
It was seen that the brains of the mice had formed, immediately and simultaneously, two traces of the event: one in the hippocampus and one in the prefrontal cortex. The engrams (memory traces) of the cortex, however, remained silent for a few days: they could be reactivated by „turning on“ the neurons with light, but were not recalled by the mice naturally.
Over the next two weeks, the silent memory neurons in the cortex solidified to allow the animal to naturally recall the trauma, while those in the hippocampus silenced, giving „the change“ to the more stable trace. However, there is an ongoing dialogue between the two areas: when the scientists inhibited the connections between the hippocampus and the cortex, the engrams of the second never matured.
Scientists have several theories as to what is behind this deterioration, starting with a shrinkage of the brain, the hippocampus loses 5% of its neurons every decade to a total loss of 20% by the time you reach 80, until it collapses. of neurotransmitters produced, such as acetylcholine, which is crucial for learning and memory. These changes seem to affect how people recall information. Age also affects the ability to create memories.
Memories are more securely encoded if we pay attention, if we are very busy, and if the information is significant. Mental and physical health problems, which tend to increase over the years, interfere with our ability to pay attention, and therefore act as memory thieves.
Chronic stress is another main cause of memory problems. If we are constantly inundated with work and personal responsibilities, our body is in hyper alert. This reaction is generated by the physiological mechanism designed to ensure that we survive in any type of crisis. Stress chemicals help move energy and increase reflexes. But, with chronic stress, the body is flooded with these chemicals, causing a loss of brain cells and the inability to form new ones, affecting the ability to retain new information.
Isolation, linked to depression, is another memory thief. A Harvard School of Public Health study found that older adults with high levels of social integration have slower memory decline over a six-year period. The exact reason is unclear, but experts suspect that social interaction offers the brain mental training. Just like muscle strength, we have to use the brain or we risk losing it. But don’t despair. There are several steps you can take to help the brain retain memories. Make sure you keep yourself physically active. An increase in blood flow to the brain is helpful. And eat well. The brain needs all the right nutrients to function properly.
Finally, keep your brain in training. Exposing the brain to challenges, such as learning a new language, is one of the best defenses for keeping memories intact.