Researchers have shown that memories can be stored in the brain and even reactivated, even though a person may not be aware of them and believes they have forgotten.

A study conducted by specialists from the University of Nottingham demonstrated that the brain is capable of “retrieving” necessary memories, even if a person cannot consciously recall them. The results of the study were published in the Journal of Neuroscience.

To observe brain activity, the researchers used magnetoencephalography (MEG) — a technology that records weak magnetic fields generated by neural activity. This method allows tracking the dynamics of so-called neural oscillations — rhythmic electrical activity in the brain, often referred to as brain waves.

These rhythms play a key role in the formation, storage, and retrieval of memories, coordinating the work of different groups of neurons.

In the experiment, participants were asked to memorize pairs of stimuli: a specific word and a short video. They were instructed to create a vivid association between them. Later, they were shown the words and asked to recall the corresponding video. Throughout this process, MEG recorded brain activity, while a specialized machine learning algorithm, trained to recognize the characteristic neural signals of each video, analyzed whether the corresponding memory was being reactivated.

The analysis showed that the brain does indeed activate memories even when a person cannot consciously recall them. However, an important difference was observed between successful and unsuccessful recall.

When a memory did reach consciousness, the neural signal appeared more rhythmically in the so-called alpha-range of brain waves. Scientists suggest that this rhythm helps the memory signal “stand out” against the background noise of neural activity.

Researchers compare this process to a stadium: if many people are talking at once, individual words are hard to distinguish, but if everyone starts singing the same song, the sound becomes clearly audible. A similar mechanism likely occurs in the brain — the rhythmic neural signal allows a memory to break through the background activity.

The scientists also found that during such rhythmic signaling, the overall level of alpha activity in the sensory areas of the cortex decreases. This is similar to the situation when overall stadium noise drops, and even a quiet choir of fans becomes noticeable.

According to the researchers, these findings may be important for understanding memory-related diseases, such as dementia. If memories continue to exist in the brain but simply do not reach consciousness, future treatments may focus not on “restoring” lost memory, but on helping existing memories surface.