Category: Memory

When we try to recall something, we reach for the ‘gist’ of it first and then try to fill in the details.

The brain works in reverse to retrieve memories, research shows.

When we try to recall something, we reach for the gist of it first and then try to fill in the details.

This is the opposite to the way we lay down memories.

When we see an object, for example, it is the details — the colours and patterns — that we notice first.

It is only slightly later in the brain, that this shape registers as a ‘dog’ or a ‘spoon’.

Mr Juan Linde-Domingo, the study’s first author, said:

“We know that our memories are not exact replicas of the things we originally experienced.

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.”

For the study, people were shown unusual objects and asked to associate them with novel names.

Later, they had to remember and reconstruct the images they had seen as best they could.

Recordings of brain activity suggested the memory process runs in reverse when people are recalling an object, said Dr Maria Wimber, study co-author:

“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.

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.”

Mr Linde-Domingo said:

“If our memories prioritise conceptual information, this also has consequences for how our memories change when we repeatedly retrieve them.

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.”

The study was published in the journal Nature Communications (Linde-Domingo et al., 2019).

We have the ability to forget traumatic memories, but it takes an effort.

Erasing a memory takes more brain power than recalling a memory, neuroscientists have found.

To forget an experience, the mind needs to focus some attention on dealing with it, but not too much.

Memories are strengthened when we linger on them for too long.

People can forget memories by redirecting their attention away from them and by actively suppressing their retrieval.

While it is hard, discarding memories is possible, the research shows.

Dr Jarrod Lewis-Peacock, study co-author, said:

“We may want to discard memories that trigger maladaptive responses, such as traumatic memories, so that we can respond to new experiences in more adaptive ways.

Decades of research has shown that we have the ability to voluntarily forget something, but how our brains do that is still being questioned.

Once we can figure out how memories are weakened and devise ways to control this, we can design treatment to help people rid themselves of unwanted memories.”

For the study, a group of people were shown pictures of faces and scenes.

Sometimes they were told to try and remember them, other times to forget them.

Brain scans revealed that people have the ability to control what they forget.

However, forgetting requires more brain activity in key areas than remembering.

Dr Tracy Wang, the study’s first author, said:

“A moderate level of brain activity is critical to this forgetting mechanism.

Too strong, and it will strengthen the memory; too weak, and you won’t modify it.

Importantly, it’s the intention to forget that increases the activation of the memory, and when this activation hits the ‘moderate level’ sweet spot, that’s when it leads to later forgetting of that experience.”

The study also found that scenes were easier to forget than faces.

Faces have more links to the emotions, which makes them lodge in the mind more easily.

Dr Lewis-Peacock said:

“This will make way for future studies on how we process, and hopefully get rid of, those really strong, sticky emotional memories, which can have a powerful impact on our health and well-being.”

The study was published in The Journal of Neuroscience (Wang et al., 2019).

Why an odour can transport our minds so quickly, much more so than a sight, sound or touch.

The parts of the brain responsible for smell and memory have a unique connectivity with each other, a study finds.

The results help explain why a smell, like that of cut grass, can so powerfully evoke a long-forgotten memory.

Dr Christina Zelano, study co-author, said:

“…smells are a profound part of memory, and odors connect us to especially important memories in our lives, often connected to loved ones.

The smell of fresh chopped parsley may evoke a grandmother’s cooking, or a whiff of a cigar may evoke a grandfather’s presence.

Odors connect us to important memories that transport us back to the presence of those people.”

The hippocampus — the area of the brain vital for memory — has direct access to the olfactory areas of the brain (those related to smell).

Other primary senses like vision, hearing and touch do not show the same strong connection with memory, the researchers found.

Dr Christina Zelano, study co-author, said:

“During evolution, humans experienced a profound expansion of the neocortex that re-organized access to memory networks.

Vision, hearing and touch all re-routed in the brain as the neocortex expanded, connecting with the hippocampus through an intermediary–association cortex–rather than directly.

Our data suggests olfaction did not undergo this re-routing, and instead retained direct access to the hippocampus.”

The study of brain scans and electrodes placed on the brain also found that the connectivity between memory and smell areas of the brain changes as people breathe in and out through their nose.

Dr Zelano said:

“This has been an enduring mystery of human experience.

Nearly everyone has been transported by a whiff of an odor to another time and place, an experience that sights or sounds rarely evoke.

Yet, we haven’t known why.

The study found the olfactory parts of the brain connect more strongly to the memory parts than other senses.

This is a major piece of the puzzle, a striking finding in humans.”

Loss of the sense of smell has become more of a focus as it is a  common symptom of COVID.

Dr Zelano said:

“Most people who lose their smell to COVID regain it, but the time frame varies widely, and some have had what appears to be permanent loss.

Loss of the sense of smell is underestimated in its impact.

It has profound negative effects of quality of life, and many people underestimate that until they experience it.

Smell loss is highly correlated with depression and poor quality of life.”

The study was published in the journal Progress in Neurobiology (Zhou et al., 2021).

With age, people’s gut becomes less healthy and this is linked to memory problems and Alzheimer’s.

Garlic could help prevent age-related memory problems by improving gut health, research suggests.

Typically, with age, people’s gut becomes less healthy and this is linked to memory problems and Alzheimer’s.

However, a compound in garlic called allyl sulfide may help support the healthy bacteria in the gut.

It restored both long- and short-term memory in the study of aging rodents.

Dr Jyotirmaya Behera, the study’s first author, said:

“Our findings suggest that dietary administration of garlic containing allyl sulfide could help maintain healthy gut microorganisms and improve cognitive health in the elderly.”

Recent research has shown that gut health affects brain health.

Dr Neetu Tyagi, study co-author, said:

“The diversity of the gut microbiota is diminished in elderly people, a life stage when neurodegenerative diseases such as Alzheimer’s and Parkinson’s develop and memory and cognitive abilities can decline.

We want to better understand how changes in the gut microbiota relate to aging-associated cognitive decline.”

The study included mice who were two-years-old, which is the mouse-equivalent of people in their 60s.

Some were fed the allyl sulfide supplement and others not.

The results showed that the garlic constituent helped restore the cognitive abilities of the senior mice.

Both their long- and short-term memory was restored by the supplement.

It is possible that garlic could be used as a treatment for memory problems linked to aging.

The study was presented at the American Physiological Society’s annual meeting  (Behera et al., 2019).