Researchers at the University of Birmingham have found that the human brain reconstructs experiences in reverse order. It first focuses on the core meaning of a visual object before recalling more specific details.
The study, published January 14th in Nature Communications, was carried out at the Centre for Human Brain Health, where researchers reconstructed the brain’s memory retrieval process via brain decoding techniques that track when a memory is being reactivated within the brain.
Finding that the brain remembers the “gist” of the object before its details is interesting because this directly opposes how the brain processes images when it first sees them. Our brains initially take in details like colors, patterns, and textures, before identifying it as a whole.
“We know that our memories are not exact replicas of the things we originally experienced,” said lead author, Juan Linde Domingo. “Memory is a reconstructive process, biased by personal knowledge and world views — sometimes we even remember events that never actually happened. But exactly how memories are reconstructed in the brain, step by step, is currently not well understood.”
To come to their conclusion, researchers asked study participants to remember a series of specific images of objects and associate each image with a word. They were then later presented with the reminder word and asked to recall the corresponding image. During this process, brain activity was monitored via electrodes and an algorithm designed to figure out which image a participant was retrieving.
“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,” said Maria Wimber, senior author of the study. “It was only later that they retrieved the specific details, for example whether they had been looking at a colour object, or a black and white outline.”
“If our memories prioritise conceptual information, this also has consequences for how our memories change when we repeatedly retrieve them,” explained Linde Domingo. “It suggests they will become more abstract and gist-like with each retrieval. Although our memories seem to appear in our ‘internal eye’ as vivid images, they are not simple snapshots from the past, but reconstructed and biased representations.”
Being able to better understand how the brain reconstructs memories is crucial for the justice system, where eyewitness testimony is so often relied on to sway jurors. More studies will have to be completed to ensure that the brain always works backwards to retrieve memories and how it reconstructs more complex memories.