Category: Memory

Certain diets can damage learning and memory, but the brain can recover, a new study finds.

High-fat diets have long been linked to all kinds of psychological problems, including depression, anxiety and learning and memory deficits.

Now, research on mice has found that memory and learning problems disappear over time, even while maintaining the high-fat diet.

In the study, some of the mice were fed a high-fat diet.

Compared with another group fed a normal diet, after three months they showed severe problems with spatial memory.

But, after 12 months, their brains seemed to have adjusted to the high-fat diet.

High-Fat Diet May Disturb a Range of Thoughts And Feelings

Ms Erica Underwood, one of the study’s author, said:

“Other factors behind the impairment must be recovering in the long term.

That’s the beautiful thing about the brain.

It can often recover or find alternate routes to allow normal function in spite of impairment.”

While the mice’s brains coped with the diet, their bodies fared less well.

The high-fat diet caused obesity and the males developed the symptoms of type-2 diabetes.

Professor Lucien Thompson, who co-authored the study, said:

“We saw that the males’ brains, as well as bodies, became insulin-insensitive.

They were producing more insulin because of the fatty diet, but not enough to cover blood glucose surges after an oral dose of glucose.

And while insulin normally stimulates hippocampal neurons, high-fat diet males stopped responding to insulin.”

Ms Underwood concluded:

“For the first time in human history we have large numbers of toddlers who are severely overweight.

It’s unprecedented.

With this new type of physiology we’re seeing, we don’t really know what’s going to happen to these children 20 or 50 years from now.”

The study was published in the journal Neural Plasticity (Underwood & Thompson, 2015).

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In a few seconds our brains can play out events that would take hours or days at real time.

The imagination has an amazing ability to compress time.

In a few seconds our brains can play out events that would take hours or days at real time.

It’s an ability we take for granted and one we need to help plan for the future.

The key to how we are able to do this is a type of brain wave which is separate to the one we use for remembering real-time experiences.

Brain cells use a series of different electrical frequencies to communicate with each other.

It’s like the way radio waves are used to communicate over long distances.

One of these frequencies, however, allows the brain to play back memories or plan future events in fast forward.

Dr Laura Colgin, one of the study’s authors, explained:

“The reason we’re excited about it is that we think this mechanism can help explain how you can imagine a sequence of events you’re about to do in a time-compressed manner.

You can plan out those events and think about the sequences of actions you’ll do.

And all of that happens on a faster time scale when you’re imagining it than when you actually go and do those things.”

It’s known that fast gamma rhythms are used to encode memories happening right now, in real time.

The researchers discovered that slow gamma rhythms are used to retrieve memories and plan for the future in fast forward.

Naturally, the extra speed causes the memories and plans to lose resolution.

It’s the same as when you compress a file on the computer and it loses some information along the way.

The findings could also have implications for mental illness, Dr Colgin thinks:

“Maybe they are transmitting their own imagined thoughts on the wrong frequency, the one usually reserved for things that are really happening.

That could have terrible consequences.”

The study was published in the journal Neuron (Zheng et al., 2016).

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Study of 3,718 older people found that, cognitively, some people’s brains were 5 years younger.

Eating vegetables — but not fruit — helps preserve memory, research finds.

The study of 3,718 people over 65 living in Chicago asked how often people ate particular foods and administered cognitive tests.

Professor Martha Clare Morris, who led the study, explained the results:

“Compared to people who consumed less than one serving of vegetables a day, people who ate at least 2.8 servings of vegetables a day saw their rate of cognitive change slow by roughly 40 percent.

This decrease is equivalent to about 5 years of younger age.”

Green leafy vegetables showed the strongest association with a better memory.

Older people in the study got the greatest benefit from eating more vegetables.

More than two servings of vegetables per day was linked to the slowest rates of cognitive decline in older people.

Professor Morris was surprised to find there was no link between fruit consumption and a preserved memory:

“This was unanticipated and raises several questions.

It may be due to vegetables containing high amounts of vitamin E, which helps lowers the risk of cognitive decline.

Vegetables, but not fruits, are also typically consumed with added fats such as salad dressings, and fats increase the absorption of vitamin E.

Further study is required to understand why fruit is not associated with cognitive change.”

The study was published in the journal Neurology (Morris et al., 2006).

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One key to learning is the exact opposite of what you’d expect.

Forgetting is a normal and necessary part of learning, a new study finds.

The instability of memory is the key to how we transfer skills and experiences to new situations, researchers have found.

Professor Edwin Robertson, from the Centre for Cognitive Neuroimaging, said:

“Our work shows that an unstable memory is a key component of the mechanism for learning transfer.

An unstable memory prevents learning from being rigidly linked to one task; instead, it allows learning to be applied flexibly.

In this study we tested the link between a memory being unstable and the transfer of learning to a different type of memory task.

We measured how learning in one task transferred to and thus improved learning in a subsequent task.

There was transfer from a motor skill to a word list task and, vice versa, from a word list to a motor skill task.

What was transferred was a high-level relationship between elements, rather than knowledge of the individual elements themselves.”

For the research, people were given the two tests 12 hours apart.

The results showed that learning between the two different tasks was only transferred when memory was unstable.

Professor Robertson said:

“Stabilised memories consistently prevented transfer to the subsequent memory task.

This suggests that the transfer of learning across diverse tasks is due to a ‘high-level representation’ that can only be formed when a memory is unstable.

Our work has identified an important function of memory instability.

An unstable memory provides a window of opportunity for communication between memories, leading to the construction of a high-level or abstract memory representation, which allows the transfer of knowledge between memory tasks.

An unstable memory is in a privileged state: only when unstable can a memory communicate with and transfer knowledge to affect the acquisition of a subsequent memory.”

The study was published in the journal Current Biology (Mosha & Robertson, 2015).

A fascinating new explanation of why our brains forget some things we’ve learned.

The brain may forget in order to save energy, a new study suggests.

So, our brains contain mechanisms that help us erase unnecessary learning.

Now scientists have uncovered how this may happen at the cellular level.

The results come from a strange finding about how we learn.

You may know the story of Pavlov’s dogs, who were taught to salivate at the ringing of a bell because they associated it with being fed.

Similarly, both humans and animals can learn to link a certain tone with a puff of air to the eyes.

This, of course, causes people to blink — it’s an automatic response.

However, you can remove the actual puff of air to the eyes and people will blink at just the sound of the tone.

They have learned to link the tone to the puff of air so they blink — even when there’s no puff.

Here’s the kink in the story, though.

When you add the puff of air back in, paradoxically people’s learning gets worse.

It’s like the extra stimulus is actually causing forgetting.

Professor Germund Hesslow, who led the new research said:

“Two stimuli therfore achieve worse results than just one.

It seems contrary to common sense, but we believe that the reason for it is that the brain wants to save energy.”

What seems to be happening is that when we’ve successfully learned a link, a neuronal braking mechanism activates.

Professor Hesslow continued:

“You could say that the part of the brain that learned the association (a part of the brain called the cerebellum) is telling its ‘teacher’: ‘I know this now, please be quiet’.

When the brain has learnt two associations, the brake becomes much more powerful.

That is why it results in forgetting, usually only temporarily, however.”

The new research describes how the nerve cells learn and forget.

Professor Hesslow said:

“Obviously, it should be important for teachers to know the mechanisms by which the brain erases the things it considers unnecessary.

You do not want to accidentally activate these mechanisms.”

The study was published in the journal PNAS (Rasmussen et al., 2015).

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Even three months later those who combined both techniques had the best recall, study finds.

Rewards combined with naps can help you learn, a new study finds.

When memories are linked to rewards, researchers found they stick better in the brain.

Adding a short nap afterwards can provide an extra boost.

Dr Kinga Igloi, who led the research, said:

“Rewards may act as a kind of tag, sealing information in the brain during learning.

During sleep, that information is favourably consolidated over information associated with a low reward and is transferred to areas of the brain associated with long-term memory.

Our findings are relevant for understanding the devastating effects that lack of sleep can have on achievement.”

In the study people were given pairs of pictures to try and remember.

Some took naps after learning, while others did not.

Sometimes participants were given small rewards after learning as well.

The study revealed that people remembered the pairs of pictures better when they received a reward.

But it was the group that slept after learning that performed the best overall.

Brain scans also showed that those who slept had higher activity in the hippocampus, an area vital to forming new memories.

People were asked back into the lab three months later for a surprise test.

Even three months later the group who were rewarded and slept after learning had the best recall.

Dr Igloi said:

“We already knew that sleep helps strengthens memories, but we now also know that it helps us select and retain those that have a rewarding value.

It makes adaptive sense that the consolidation of memory should work to prioritise information that is critical to our success and survival.”

The study was published in the journal eLife (Igloi et al., 2015).

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The mental health problem that affects at least one in six people in their lifetime.

People with recurrent depression have a smaller hippocampus, a new study finds.

The hippocampus is part of the brain most strongly linked to forming new memories.

The study may help to explain some of the typical, but lesser known symptoms of depression.

People experiencing depression have particular problems with declarative memory, which is the memory for specific facts like names or places.

Depression blurs other types of memory as well, including the ability to recall meanings and to navigate through space.

Precisely because of memory difficulties and depressed mood, it can be difficult for depressed people to remember the good times.

The findings about the hippocampus come from a study which looked at the brain scans of almost 9,000 people around the world.

Neuroscientists compared the brains of healthy individuals with those who have major depression.

Major depression will affect at least one in six people in their lifetime.

The condition typically returns for weeks, months or even years at a time.

A handful of the emotional symptoms include sadness, anger, frustration and loss.

There are many other less-known symptoms like sleeping problems and changes to appetite (see: 5 Classic Signs of Depression Most People Don’t Recognise).

Dr Jim Lagopoulos, one of the study’s authors, said:

“These findings shed new light on brain structures and possible mechanisms responsible for depression.

Despite intensive research aimed at identifying brain structures linked to depression in recent decades, our understanding of what causes depression is still rudimentary.

One reason for this has been the lack of sufficiently large studies, variability in the disease and treatments provided, and the complex interactions between clinical characteristics and brain structure.”

Dr Lagopoulos continued:

“This new finding of smaller hippocampal volume in people with major depression may offer some support to the neurotrophic hypothesis of depression.

This hypothesis argues that a range of neurobiological processes such as elevated glucocorticoid levels in those with chronic depression may induce brain shrinkage.

Clearly, there’s a need for longitudinal studies that can track changes in hippocampal volume among people with depression over time, to better clarify whether hippocampal abnormalities result from prolonged duration of chronic stress, or represent a vulnerability factor for depression, or both.”

• Depression: 10 Fascinating Insights into a Misunderstood Condition

The study was published in the journal Molecular Psychiatry (Schmaal et al., 2015).

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