How do our brains remember?

The way in which our brains retrieve memories is still quite poorly understood, and we often remember moments and events in a general fashion, without recalling exact details. Why is that? New research (Nature Communications volume 10, Article number: 179 (2019)) pins down the steps of simple memory recall.

"We know that our memories are not exact replicas of the things we originally experienced," says Juan Linde-Domingo, a researcher from the School of Psychology & Centre for Human Brain Health at the University of Birmingham in the United Kingdom.

Linde-Domingo and colleagues from the University of Birmingham and the Cardiff University Brain Research Imaging Centre, in Wales, recently investigated how our brains recall set memories and what this shows about the way in which we remember events.

"Memory is a reconstructive process, biased by personal knowledge and worldviews - sometimes we even remember events that never actually happened," says lead author Linde-Domingo, though, he adds, "exactly how memories are reconstructed in the brain, step by step, is currently not well-understood."

This is what the researchers have been trying to determine by "decoding" the process through which the brain finds and reconstructs memories.

The researchers found that the participants recalled more abstract information first - for example, whether the image was of an animal or a musical instrument. However, they noticed that the participants' brains did not recall any details of the object's appearance at first - this step, the investigators say, came later.

"We were able to show that the participants were retrieving higher-level abstract information, such as whether they were thinking of an animal or an inanimate object, shortly after they heard the reminder word," notes the study's senior author, neuroscientist Maria Wimber, Ph.D.

"It was only later that they retrieved the specific details, for example whether they had been looking at a color object or a black-and-white outline," she adds.

When a person sees a complex object for the first time, the investigators explain, the brain initially records the small details, such as color schemes or patterns.

Only afterward does the brain take note of the abstract category to which the object belongs - such as animal, plant, or piece of furniture.

"If our memories prioritize conceptual information, this also has consequences for how our memories change when we repeatedly retrieve them," explains Linde-Domingo, adding, "it suggests they will become more abstract and gist-like with each retrieval."