Adonis Diaries

Posts Tagged ‘hippocampus

And what are the Brain cells Survival Skills?

Posted on March 4, 2013

Fear beyond the Amygdala
Ranya Bechara posted on Feb. 6, 2013

Picture

For decades now, scientists have thought that fear could not be experienced without the amygdala.

This almond-shaped structure located deep in the brain (pictured on the left). The amygdala has been shown to play an important role in fear-related behaviours, emotions, and memories, and patients with damage to the amygdala on both sides of the brain were thought to be incapable of feeling afraid.

However, a recent study in Nature Neuroscience reports that these ‘fearless’ patients do experience fear if made to inhale carbon dioxide- a procedure that induces feelings of suffocation and panic.

The patients reported being quite surprised at their own fear, and that it was a novel experience for them!

Scientists behind the study have suggested that the way the brain processes fear information depends on the type of stimulus. The results of this study could have important implications for people who suffer from anxiety disorders such as panic attacks and post-traumatic stress disorder (PTSD).

More details can be found here

And how the brain can momentarily react to oxygen deficiency from Strokes?

Can scientists use the brain’s inherent survival mechanisms to develop better stroke treatment?

Strokes are a major cause of death and disability worldwide, with 150,000 people affected in the UK every year.

Most strokes happen when a blood vessel that supplies blood to the brain is blocked due to blood clots or fat deposits. Once blood is cut off from an area of the brain, brain cells are starved for oxygen and nutrients and start to die within minutes.

A new study in Nature Medicine, scientists at the University of Oxford reveal a novel way in which the brain protects itself in response to stroke.

Ranya Bechara posted on Feb. 27, 2013 “Stroke Vs Brain: Harnessing the Brain’s Survival Skills”

Current treatments for stroke are focussed on breaking up the clots, improving blood flow to the affected area, and ultimately reducing the brain damage caused by the stroke. However, the so called ‘clot-busters’ are only effective if given within one to two hours of the stroke.

Other ways of protecting the brain against stroke damage are in high demand.

In this study, the research team from Oxford University (in collaboration with other researchers from Greece, Germany, and Canada, and the UK) decided to try a new approach. They investigated a phenomenon that has been known for years: some brain cells have an inherent defence mechanism that allows them to survive when deprived of oxygen.

These cells are located in the part of the brain responsible for forming memories: a pretty sea-horse shaped structure called the hippocampus.

The scientists analysed the proteins produced by these cells and found that the key to their survival is a protein called hamartin. This protein is released by the cells in response to oxygen deprivation, and when its production was suppressed, the cells became more vulnerable to the effects of stroke.

Original article is available here

Photo credit: http://www.vascularinfo.co.uk

Picture

First Human Tests of Memory Boosting Brain Implant a Big Leap Forward

Every year, hundreds of millions of people experience the pain of a failing memory.

“You have to begin to lose your memory, if only bits and pieces, to realize that memory is what makes our lives. Life without memory is no life at all.” — Luis Buñuel Portolés, Filmmaker

The reasons are many: traumatic brain injury, which haunts a disturbingly high number of veterans and football players; stroke or Alzheimer’s disease, which often plagues the elderly; or even normal brain aging, which inevitably touches us all.

Memory loss seems to be inescapable. But one maverick neuroscientist is working hard on an electronic cure.

Funded by DARPA, Dr. Theodore Berger, a biomedical engineer at the University of Southern California, is testing a memory-boosting implant that mimics the kind of signal processing that occurs when neurons are laying down new long-term memories.

The revolutionary implant, already shown to help memory encoding in rats and monkeys, is now being tested in human patients with epilepsy — an exciting first that may blow the field of memory prosthetics wide open.

To get here, however, the team first had to crack the memory code.

Deciphering Memory

From the very onset, Berger knew he was facing a behemoth of a problem.

We weren’t looking to match everything the brain does when it processes memory, but to at least come up with a decent mimic, said Berger.

“Of course people asked: can you model it and put it into a device? Can you get that device to work in any brain? It’s those things that lead people to think I’m crazy. They think it’s too hard,” he said.

But the team had a solid place to start.

The hippocampus, a region buried deep within the folds and grooves of the brain, is the critical gatekeeper that transforms memories from short-lived to long-term. In dogged pursuit, Berger spent most of the last 35 years trying to understand how neurons in the hippocampus accomplish this complicated feat.

At its heart, a memory is a series of electrical pulses that occur over time that are generated by a given number of neurons, said Berger. This is important — it suggests that we can reduce it to mathematical equations and put it into a computational framework, he said.

Berger hasn’t been alone in his quest.

By listening to the chatter of neurons as an animal learns, teams of neuroscientists have begun to decipher the flow of information within the hippocampus that supports memory encoding. Key to this process is a strong electrical signal that travels from CA3, the “input” part of the hippocampus, to CA1, the “output” node.

This signal is impaired in people with memory disabilities, said Berger, so of course we thought if we could recreate it using silicon, we might be able to restore — or even boost — memory.

Bridging the Gap

Yet this brain’s memory code proved to be extremely tough to crack.

The problem lies in the non-linear nature of neural networks: signals are often noisy and constantly overlap in time, which leads to some inputs being suppressed or accentuated. In a network of hundreds and thousands of neurons, any small change could be greatly amplified and lead to vastly different outputs.

It’s a chaotic black box, laughed Berger.

With the help of modern computing techniques, however, Berger believes he may have a crude solution in hand. His proof?

Use his mathematical theorems to program a chip, and then see if the brain accepts the chip as a replacement — or additional — memory module.

Berger and his team began with a simple task using rats.

They trained the animals to push one of two levers to get a tasty treat, and recorded the series of CA3 to CA1 electronic pulses in the hippocampus as the animals learned to pick the correct lever. The team carefully captured the way the signals were transformed as the session was laid down into long-term memory, and used that information — the electrical “essence” of the memory — to program an external memory chip.

They then injected the animals with a drug that temporarily disrupted their ability to form and access long-term memories, causing the animals to forget the reward-associated lever.

Next, implanting microelectrodes into the hippocampus, the team pulsed CA1, the output region, with their memory code.

The results were striking — powered by an external memory module, the animals regained their ability to pick the right lever.

Encouraged by the results, Berger next tried his memory implant in monkeys, this time focusing on a brain region called the prefrontal cortex, which receives and modulates memories encoded by the hippocampus.

Placing electrodes into the monkey’s brains, the team showed the animals a series of semi-repeated images, and captured the prefrontal cortex’s activity when the animals recognized an image they had seen earlier.

with a hefty dose of cocaine, the team inhibited that particular brain region, which disrupted the animal’s recall.

Next, using electrodes programmed with the “memory code,” the researchers guided the brain’s signal processing back on track — and the animal’s performance improved significantly.

A year later, the team further validated their memory implant by showing it could also rescue memory deficits due to hippocampal malfunction in the monkey brain.

A Human Memory Implant

Last year, the team cautiously began testing their memory implant prototype in human volunteers.

Because of the risks associated with brain surgery, the team recruited 12 patients with epilepsy, who already have electrodes implanted into their brain to track down the source of their seizures.

Repeated seizures steadily destroy critical parts of the hippocampus needed for long-term memory formation, explained Berger. So if the implant works, it could benefit these patients as well.

The team asked the volunteers to look through a series of pictures, and then recall which ones they had seen 90 seconds later. As the participants learned, the team recorded the firing patterns in both CA1 and CA3 — that is, the input and output nodes.

Using these data, the team extracted an algorithm — a specific human “memory code” — that could predict the pattern of activity in CA1 cells based on CA3 input.

Compared to the brain’s actual firing patterns, the algorithm generated correct predictions roughly 80% of the time.

It’s not perfect, said Berger, but it’s a good start.

Using this algorithm, the researchers have begun to stimulate the output cells with an approximation of the transformed input signal.

We have already used the pattern to zap the brain of one woman with epilepsy, said Dr. Dong Song, an associate professor working with Berger. But he remained coy about the result, only saying that although promising, it’s still too early to tell.

Song’s caution is warranted. Unlike the motor cortex, with its clear structured representation of different body parts, the hippocampus is not organized in any obvious way.

It’s hard to understand why stimulating input locations can lead to predictable results, said Dr. Thoman McHugh, a neuroscientist at the RIKEN Brain Science Institute. It’s also difficult to tell whether such an implant could save the memory of those who suffer from damage to the output node of the hippocampus.

“That said, the data is convincing,” McHugh acknowledged.

Berger, on the other hand, is ecstatic. “I never thought I’d see this go into humans,” he said.

But the work is far from done.

Within the next few years, Berger wants to see whether the chip can help build long-term memories in a variety of different situations. After all, the algorithm was based on the team’s recordings of one specific task — what if the so-called memory code is not generalizable, instead varying based on the type of input that it receives?

Berger acknowledges that it’s a possibility, but he remains hopeful.

I do think that we will find a model that’s a pretty good fit for most conditions, he said. After all, the brain is restricted by its own biophysics — there’s only so many ways that electrical signals in the hippocampus can be processed, he said.

“The goal is to improve the quality of life for somebody who has a severe memory deficit,” said Berger.

“If I can give them the ability to form new long-term memories for half the conditions that most people live in, I’ll be happy as hell, and so will be most patients.”

What are the Brain’s Survival Skills? And Fear beyond the Amygdala

Can scientists use the brain’s inherent survival mechanisms to develop better stroke treatment?

Strokes are a major cause of death and disability worldwide, with 150,000 people affected in the UK every year.

Most strokes happen when a blood vessel that supplies blood to the brain is blocked due to blood clots or fat deposits. Once blood is cut off from an area of the brain, brain cells are starved for oxygen and nutrients and start to die within minutes.

A new study in Nature Medicine, scientists at the University of Oxford reveal a novel way in which the brain protects itself in response to stroke.

Ranya Bechara posted on Feb. 27, 2013 “Stroke Vs Brain: Harnessing the Brain’s Survival Skills”

Current treatments for stroke are focussed on breaking up the clots, improving blood flow to the affected area, and ultimately reducing the brain damage caused by the stroke. However, the so called ‘clot-busters’ are only effective if given within one to two hours of the stroke.

Other ways of protecting the brain against stroke damage are in high demand.

In this study, the research team from Oxford University (in collaboration with other researchers from Greece, Germany, and Canada, and the UK) decided to try a new approach. They investigated a phenomenon that has been known for years: some brain cells have an inherent defence mechanism that allows them to survive when deprived of oxygen.

These cells are located in the part of the brain responsible for forming memories: a pretty sea-horse shaped structure called the hippocampus.

The scientists analysed the proteins produced by these cells and found that the key to their survival is a protein called hamartin. This protein is released by the cells in response to oxygen deprivation, and when its production was supressed, the cells became more vulnerable to the effects of stroke.

Photo credit: http://www.vascularinfo.co.uk

Picture  





Original article is available here

Fear beyond the Amygdala
Ranya Bechara posted on Feb. 6, 2013

Picture

For decades now, scientists have thought that fear could not be experienced without the amygdala. This almond-shaped structure located deep in the brain (pictured on the left).
The amygdala has been shown to play an important role in fear-related behaviours, emotions, and memories, and patients with damage to the amygdala on both sides of the brain were thought to be incapable of feeling afraid.
However, a recent study in Nature Neuroscience reports that these ‘fearless’ patients do experience fear if made to inhale carbon dioxide- a procedure that induces feelings of suffocation and panic.
The patients reported being quite surprised at their own fear, and that it was a novel experience for them!
Scientists behind the study have suggested that the way the brain processes fear information depends on the type of stimulus.
The results of this study could have important implications for people who suffer from anxiety disorders such as panic attacks and post-traumatic stress disorder (PTSD).
More details can be found here

Science says: No recollection of the past, no future projects (October 7, 2008)

Neuroscientists, using MRI technology, discovered that the same regions in the brain that recollect the past are the ones that also activate during project development.

The pre-frontal Cortex that refers to the self or the evocation of personal events (for example what happened last week), and the hippocampus that recollects the past are also active when thinking of intended projects for the next week.

Thus, memory is basic to our coherence, our reason, our feelings, and also our action.

Without memory, we have no individuality and we are practically nothing.

My suggestion is to write diaries with some details because, most likely, it will guide or determine to a large extent our brain to plan and to affect our next projects.

Let me offer a plausible extrapolation.

It has been done, for many who lost their biographical memory, to re-construct a new memory out of pictures, videos and other materials.  Obviously, the person has no faculty to verify if his new acquired memory is factual.

Consequently, the historians, formally appointed to write history books for students, have a large latitude to affect subconsciously the opinions of new generations on the internal and external policies of the authorities.

Taking the plausible extrapolation further, and recognizing that history is written by the victors, it is more than likely that nationalist feelings among the victorious nations are biased toward fascist tendencies, and the citizens are prone to casually accept unilateral military actions against weakling nations.


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