Scientists explained the deterioration of memory during aging by overactivity of dopamine

Japanese scientists have found that age—related decline in long-term memory is not caused by its disappearance, but by generalization, a condition in which the brain reproduces memories in response to inappropriate stimuli. The results of the work were published on April 1 in the journal PLoS Biology.

"Our data indicate that increased activity of dopaminergic neurons after exercise generalizes the susceptibility of engram cells and disrupts the normal reproduction of memory," the authors of the study said.

Experiments were conducted on fruit flies, drosophila, which were trained to avoid a certain odor, accompanied by electric shocks. In young individuals, memory cells — engrams — were activated strictly when they encountered a trained odor. In old flies, the same cells reacted equally to both trained and unfamiliar odors, which is why the insects avoided any stimuli indiscriminately.

Researchers have found that with age, the brain does not forget, but gets confused. After training, young flies clearly remembered the "dangerous" smell and reacted only to it. The old flies reacted to everything: to a familiar smell, and to an unfamiliar one. Their memory seemed to "blur" — instead of an accurate memory, a vague sense of danger was formed without reference to a specific stimulus.

Brains in a jar: how cryopreservation will change medicine

Scientists have tested immortality on laboratory mice

Scientists found the reason in a chain of failures inside the brain. Normally, after learning, auxiliary brain cells — glia — remove excess glutamate, an excitatory substance that mediates between neurons. This calms a certain group of neurons that would otherwise release too much dopamine. In old flies, glia cannot cope with this task: glutamate accumulates, neurons become overexcited, dopamine becomes too much and memory cells lose selectivity, starting to respond to any stimulus.

When the researchers artificially blocked this glitch, using drugs or genetic tools, the old flies began to accurately recognize the "right" smell again.

The authors noted that a similar mechanism seems to work in humans: with age, a person's memories also become less accurate, and with PTSD, the brain even perceives harmless situations as dangerous — according to the same logic of "blurred" memory.

Neuroscientist Christian Jarrett explained in Science Focus on March 29 which six daily habits help maintain cognitive function and reduce the risk of dementia with age.

All important news is on the Izvestia channel in the MAX messenger.