Posts Tagged ‘hippocampus’

by Bahar Golipour

What is the earliest memory you have?

Most people can’t remember anything that happened to them or around them in their toddlerhood. The phenomenon, called childhood amnesia, has long puzzled scientists. Some have debated that we forget because the young brain hasn’t fully developed the ability to store memories. Others argue it is because the fast-growing brain is rewiring itself so much that it overwrites what it’s already registered.

New research that appears in Nature Neuroscience this week suggests that those memories are not forgotten. The study shows that when juvenile rats have an experience during this infantile amnesia period, the memory of that experience is not lost. Instead, it is stored as a “latent memory trace” for a long time. If something later reminds them of the original experience, the memory trace reemerges as a full blown, long-lasting memory.

Taking a (rather huge) leap from rats to humans, this could explain how early life experiences that you don’t remember still shape your personality; how growing up in a rich environment makes you a smarter person and how early trauma puts you at higher risk for mental health problems later on.

Scientists don’t know whether we can access those memories. But the new study shows childhood amnesia coincides with a critical time for the brain ― specifically the hippocampus, a seahorse-shaped brain structure crucial for memory and learning. Childhood amnesia corresponds to the time that your brain matures and new experiences fuel the growth of the hippocampus.

In humans, this period occurs before pre-school, likely between the ages 2 and 4. During this time, a child’s brain needs adequate stimulation (mostly from healthy social interactions) so it can better develop the ability to learn.

And not getting enough healthy mental activation during this period may impede the development of a brain’s learning and memory centers in a way that it cannot be compensated later.

“What our findings tell us is that children’s brains need to get enough and healthy activation even before they enter pre-school,” said study leader Cristina Alberini, a professor at New York University’s Center for Neural Science. “Without this, the neurological system runs the risk of not properly developing learning and memory functions.”

The findings may illustrate one mechanism that could in part explain scientific research that shows poverty can shrink children’s brains.

Extensive research spanning decades has shown that low socioeconomic status is linked to problems with cognitive abilities, higher risk for mental health issues and poorer performance in school. In recent years, psychologists and neuroscientists have found that the brain’s anatomy may look different in poor children. Poverty is also linked to smaller brain surface area and smaller volume of the white matter connecting brain areas, as well as smaller hippocampus. And a 2015 study found that the differences in brain development explain up to 20 percent of academic performance gap between children from high- and low-income families.

Critical Periods

For the brain, the first few years of life set the stage for the rest of life.

Even though the nervous system keeps some of its ability to rewire throughout life, several biochemical events that shape its core structure happen only at certain times. During these critical periods of the developmental stages, the brain is acutely sensitive to new sights, sounds, experiences and external stimulation.

Critical periods are best studied in the visual system. In the 1960s, scientists David Hubel and Torsten Wiesel showed that if they close one eye of a kitten from birth for just for a few months, its brain never learns to see properly. The neurons in the visual areas of the brain would lose their ability respond to the deprived eye. Adult cats treated the same way don’t show this effect, which demonstrates the importance of critical periods in brain development for proper functioning. This finding was part of the pioneering work that earned Hubel and Wiesel the 1981 Nobel Prize in Physiology or Medicine.

In the new study in rats, the team shows that a similar critical period may be happening to the hippocampus.

Alberini and her colleagues took a close look at what exactly happens in the brain of rats in their first 17 days of life (equivalent to the first three years of a human’s life). They created a memory for the rodents of a negative experience: every time the animals entered a specific corner of their cage, they received a mildly painful shock to their foot. Young rats, like kids, aren’t great at remembering things that happened to them during their infantile amnesia. So although they avoided that corner right after the shock, they returned to it only a day later. In contrast, a group of older rats retained the memory and avoided this place for a long time.

However, the younger rats, had actually kept a trace of the memory. A reminder (such as another foot shock in another corner) was enough to resurrect the memory and make the animals avoid the first corner of the cage.

Researchers found a cascade of biochemical events in the young rats’ brains that are typically seen in developmental critical periods.

“We were excited to see the same type of mechanism in the hippocampus,” Alberini told The Huffington Post.

The Learning Brain And Its Mysteries

Just like the kittens’ brain needed light from the eyes to learn to see, the hippocampus may need novel experiences to learn to form memories.

“Early in life, while the brain cannot efficiently form long-term memories, it is ‘learning’ how to do so, making it possible to establish the abilities to memorize long-term,” Alberini said. “However, the brain needs stimulation through learning so that it can get in the practice of memory formation―without these experiences, the ability of the neurological system to learn will be impaired.”

This does not mean that you should put your kids in pre-pre-school, Alberini told HuffPost. Rather, it highlights the importance of healthy social interaction, especially with parents, and growing up in an environment rich in stimulation. Most kids in developed countries are already benefiting from this, she said.

But what does this all mean for children who grow up exposed to low levels of environmental stimulation, something more likely in poor families? Does it explain why poverty is linked to smaller brains? Alberini thinks many other factors likely contribute to the link between poverty and brain. But it is possible, she said, that low stimulation during the development of the hippocampus, too, plays a part.

Psychologist Seth Pollak of University of Wisconsin at Madison who has found children raised in poverty show differences in hippocampal development agrees.

Pollak believes the findings of the new study represent “an extremely plausible link between early childhood adversity and later problems.”

“We must always be cautious about generalizing studies of rodents to understanding human children,” Pollas added. “But the nonhuman animal studies, such as this one, provide testable hypotheses about specific mechanisms underlying human behavior.”

Although the link between poverty and cognitive performance has been repeatedly seen in numerous studies, scientists don’t have a good handle on how exactly many related factors unfold inside the developing brain, said Elizabeth Sowell, a researcher from the Children’s Hospital Los Angeles. Studies like this one provide “a lot of food for thought,” she added.

http://www.huffingtonpost.com.au/2016/07/24/the-things-you-dont-remember-shape-who-you-are/

To investigate whether the differences in how men and women navigate are related to our sex or to cultural conditioning, researchers in Norway measured male and female brain activity while volunteers tried to find their way through a virtual reality maze.

Wearing 3D goggles and using a joystick to make their way through an artificial environment, the participants (18 males and 18 females) had their brain functions continuously recorded by an fMRI scanner as they carried out virtual navigation tasks.

In line with previous findings, the men performed better, using shortcuts, orienting themselves more using cardinal directions, and solving 50 percent more tasks than the women in the study.

“Men’s sense of direction was more effective,” said Carl Pintzka, a neuroscientist at the Norwegian University of Science and Technology (NTNU). “They quite simply got to their destination faster.”

One of the reasons for this is because of the difference in how men and women use their brains when we’re finding our way around. According to the researchers, men use the hippocampus more, whereas women place greater reliance on their brains’ frontal areas.

“That’s in sync with the fact that the hippocampus is necessary to make use of cardinal directions,” said Pintzka. “[M]en usually go in the general direction where [their destination is] located. Women usually orient themselves along a route to get there.”

Generally, the cardinal approach is more efficient, as it depends less on where you start.

But women’s brains make them better at finding objects locally, the researchers say. “In ancient times, men were hunters and women were gatherers. Therefore, our brains probably evolved differently,” said Pintzka. “In simple terms, women are faster at finding things in the house, and men are faster at finding the house.”

What was most remarkable about the study was what happened when the researchers gave women a drop of testosterone to see how it affected their ability to navigate the virtual maze. In a separate experiment, 21 women received a drop of testosterone under their tongues, while 21 got a placebo.

The researchers found that the women receiving testosterone showed improved knowledge of the layout of the maze, and relied on their hippocampus more to find their way around. Having said that, these hormone-derived benefits didn’t enable them to solve more maze tasks in the exercise.

It’s worth bearing in mind that the study used a fairly small sample size in both of the experiments carried out, so the findings need to be read in light of that. Nonetheless, the scientists believe their paper, which is published in Behavioural Brain Research, will help us to better understand the different ways male and female brains work, which could assist in the fight against diseases such as Alzheimer’s.

“Almost all brain-related diseases are different in men and women, either in the number of affected individuals or in severity,” said Pintzka. “Therefore, something is likely protecting or harming people of one sex. Since we know that twice as many women as men are diagnosed with Alzheimer’s disease, there might be something related to sex hormones that is harmful.”

http://www.sciencealert.com/women-can-navigate-better-when-given-testosterone-study-finds

Thanks to Dr. Enrique Leira for bringing this to the It’s Interesting community.

Researchers at University of South Carolina (USC) and Wake Forest Baptist Medical Center have developed a brain prosthesis that is designed to help individuals suffering from memory loss.

The prosthesis, which includes a small array of electrodes implanted into the brain, has performed well in laboratory testing in animals and is currently being evaluated in human patients.

Designed originally at USC and tested at Wake Forest Baptist, the device builds on decades of research by Ted Berger and relies on a new algorithm created by Dong Song, both of the USC Viterbi School of Engineering. The development also builds on more than a decade of collaboration with Sam Deadwyler and Robert Hampson of the Department of Physiology & Pharmacology of Wake Forest Baptist who have collected the neural data used to construct the models and algorithms.

When your brain receives the sensory input, it creates a memory in the form of a complex electrical signal that travels through multiple regions of the hippocampus, the memory center of the brain. At each region, the signal is re-encoded until it reaches the final region as a wholly different signal that is sent off for long-term storage.

If there’s damage at any region that prevents this translation, then there is the possibility that long-term memory will not be formed. That’s why an individual with hippocampal damage (for example, due to Alzheimer’s disease) can recall events from a long time ago – things that were already translated into long-term memories before the brain damage occurred – but have difficulty forming new long-term memories.

Song and Berger found a way to accurately mimic how a memory is translated from short-term memory into long-term memory, using data obtained by Deadwyler and Hampson, first from animals, and then from humans. Their prosthesis is designed to bypass a damaged hippocampal section and provide the next region with the correctly translated memory.

That’s despite the fact that there is currently no way of “reading” a memory just by looking at its electrical signal.

“It’s like being able to translate from Spanish to French without being able to understand either language,” Berger said.

Their research was presented at the 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society in Milan on August 27, 2015.

The effectiveness of the model was tested by the USC and Wake Forest Baptist teams. With the permission of patients who had electrodes implanted in their hippocampi to treat chronic seizures, Hampson and Deadwyler read the electrical signals created during memory formation at two regions of the hippocampus, then sent that information to Song and Berger to construct the model. The team then fed those signals into the model and read how the signals generated from the first region of the hippocampus were translated into signals generated by the second region of the hippocampus.

In hundreds of trials conducted with nine patients, the algorithm accurately predicted how the signals would be translated with about 90 percent accuracy.

“Being able to predict neural signals with the USC model suggests that it can be used to design a device to support or replace the function of a damaged part of the brain,” Hampson said.
Next, the team will attempt to send the translated signal back into the brain of a patient with damage at one of the regions in order to try to bypass the damage and enable the formation of an accurate long-term memory.

http://medicalxpress.com/news/2015-09-scientists-bypass-brain-re-encoding-memories.html#nRlv

A pioneering study conducted by leading researchers at the University of Sheffield has revealed blood types play a role in the development of the nervous system and may impact the risk of developing cognitive decline.

The research, carried out in collaboration with the IRCCS San Camillo Hospital Foundation in Venice, shows that people with an ‘O’ blood type have more grey matter in their brain, which helps to protect against diseases such as Alzheimer’s, than those with ‘A’, ‘B’ or ‘AB’ blood types.

Research fellow Matteo De Marco and Professor Annalena Venneri, from the University’s Department of Neuroscience, made the discovery after analysing the results of 189 Magnetic Resonance Imaging (MRI) scans from healthy volunteers.

The researchers calculated the volumes of grey matter within the brain and explored the differences between different blood types.

The results, published in the Brain Research Bulletin, show that individuals with an ‘O’ blood type have more grey matter in the posterior proportion of the cerebellum.

In comparison, those with ‘A’, ‘B’ or ‘AB’ blood types had smaller grey matter volumes in temporal and limbic regions of the brain, including the left hippocampus, which is one of the earliest part of the brain damaged by Alzheimer’s disease.

These findings indicate that smaller volumes of grey matter are associated with non-‘O’ blood types.

As we age a reduction of grey matter volumes is normally seen in the brain, but later in life this grey matter difference between blood types will intensify as a consequence of ageing.

“The findings seem to indicate that people who have an ‘O’ blood type are more protected against the diseases in which volumetric reduction is seen in temporal and mediotemporal regions of the brain like with Alzheimer’s disease for instance,” said Matteo DeMarco.

“However additional tests and further research are required as other biological mechanisms might be involved.”

Professor Annalena Venneri added: “What we know today is that a significant difference in volumes exists, and our findings confirm established clinical observations. In all likelihood the biology of blood types influences the development of the nervous system. We now have to understand how and why this occurs.”

More information: “‘O’ blood type is associated with larger grey-matter volumes in the cerebellum,” Brain Research Bulletin, Volume 116, July 2015, Pages 1-6, ISSN 0361-9230, dx.doi.org/10.1016/j.brainresbull.2015.05.005

Everyone knows it’s easier to learn about a topic you’re curious about. Now, a new study reveals what’s going on in the brain during that process, revealing that such curiosity may give a person a memory boost.

When participants in the study were feeling curious, they were better at remembering information even about unrelated topics, and brain scans showed activity in areas linked to reward and memory.

The results, detailed October 2 in the journal Neuron, hint at ways to improve learning and memory in both healthy people and those with neurological disorders, the researchers said.

“Curiosity may put the brain in a state that allows it to learn and retain any kind of information, like a vortex that sucks in what you are motivated to learn, and also everything around it,” Matthias Gruber, a memory researcher at the University of California, Davis, said in a statement. “These findings suggest ways to enhance learning in the classroom and other settings.”

Gruber and his colleagues put people in a magnetic resonance imaging (MRI) scanner and showed them a series of trivia questions, asking them to rate their curiosity about the answers to those questions. Later, the participants were shown selected trivia questions, then a picture of a neutral face during a 14-second delay, followed by the answer. Afterward, the participants were given a surprise memory test of the faces, and then a memory test of the trivia answers.

Not surprisingly, the study researchers found that people remembered more information about the trivia when they were curious about the trivia answers. But unexpectedly, when the participants were curious, they were also better at remembering the faces, an entirely unrelated task. Participants who were curious were also more likley than others to remember both the trivia information and unrelated faces a day later, the researchers found.

The brain scans showed that, compared with when their curiosity wasn’t piqued, when people were curious, they showed more activation of brain circuits in the nucleus accumbens, an area involved in reward. These same circuits, mediated by the neurochemical messenger dopamine, are involved in forms of external motivation, such as food, sex or drug addiction.

Finally, being curious while learning seemed to produce a spike of activity in the hippocampus, an area involved in forming new memories, and strengthened the link between memory and reward brain circuits.

The study’s findings not only highlight the importance of curiosity for learning in healthy people, but could also give insight into neurological conditions. For example, as people age, their dopamine circuits tend to deteriorate, so understanding how curiosity affects these circuits could help scientists develop treatments for patients with memory disorders, the researchers said.

http://www.livescience.com/48121-curiosity-boosts-memory-learning.html