Tag Archives: #different

Researchers Reveal How Our Brains Know When Something’s Different (Neuroscience)

Imagine you are sitting on the couch in your living room reading. You do it almost every night. But then, suddenly, when you look up you notice this time something is different. Your favorite picture hanging on the wall is tilted ever so slightly. In a study involving epilepsy patients, National Institutes of Health scientists discovered how a set of high frequency brain waves may help us spot these kinds of differences between the past and the present.

NIH scientists discovered how a set of high frequency brain waves may help us unconsciously set expectations of the world around us and know when something’s different by comparing memories of the past with present experiences. Credit: Zaghloul lab, NIH/NINDS.

“Our results suggest that every experience we store into memory can be used to set our expectations and predictions for the future,” Kareem Zaghloul, M.D., Ph.D., principal investigator at the NIH’s National Institute of Neurological Disorders and Stroke (NINDS), and senior author of the study published in Nature Communications. “This study shows how the brain uses certain neural activity patterns to compare our expectations with the present. Ultimately, we hope that these results will help us better understand how the brain portrays reality under healthy and disease conditions.”

The study was led by Rafi Haque, an M.D., Ph.D. student at Emory University School of Medicine, Atlanta, who was completing his dissertation work with Dr. Zaghloul. His primary research goal was to test out whether a theory called predictive coding can be applied to how our brains remember past experiences, known as episodic memories.

“Predictive coding basically states that the brain optimizes neural activity for processing information. In other words, the theory forecasts that the brain uses more neural activity to process new information than it does for things that we are familiar with,” said Dr. Haque. “Years of research has shown that over time this is how we learn to expect what common sights, like green grass, looks like or everyday noises, such as certain bird chirps, sound like. We wanted to know whether the brain uses a similar process to manage our experiences.”

To test this idea, the team worked with 14 patients with drug-resistant types of epilepsy whose brains had been surgically implanted with grids of electrodes as part of an NIH Clinical Center trial aimed at diagnosing and treating their seizures.

The experiment began when the patients were shown and asked to memorize a series of four natural scenes displayed on a computer screen. For example, one of the scenes was of a brown bicycle leaning upright on a kickstand in front of a green bush. A few seconds later they were shown a new set of images and asked whether they recognized the scene or noticed something different. Some images were the same as before while others were slightly modified by adding or removing something, such as a red bird, from the scene.

On average, the patients successfully recognized 88% of the repeat scenes, 68% of scenes that were missing something, and 65% of the ones in which something was added. In each case, it took them about two and a half seconds to notice.

Further analysis of a subset of the patients showed that they successfully located 82% of additions and 70% of removals. Curiously, their eyes fixated often (83%) on additions but barely at all (34%) on areas in the scene where something was removed.

“Overall, these results suggest it takes just one moment to not only remember a new experience but also to use memories of that experience to set future expectations,” said Dr. Zaghloul.

Meanwhile, electrical recordings uncovered differences in brain wave activity between the times the patients successfully remembered repeat scenes and the times they spotted changes to a scene.

In both situations, the appearance of a scene on the computer screen triggered a rise in the strength of high frequency waves of neural activity in the lateral occipital cortex, a visual processing center in the back of the brain. The surge flowed forward arriving a few milliseconds later at a memory center called the medial temporal lobe.

Also, in both situations, the patients’ brains appeared to replay neural activity patterns observed when they first witnessed the scenes.

“These results support the idea that memories of visual experiences follow a certain pathway in the brain,” said Dr. Haque.

The difference though was that the surge in activity was stronger when the patients recognized a change to a scene.

In addition, during these moments, a second, lower frequency wave appeared to synchronously rumble through the lateral occipital cortex and the medial temporal lobe.

“Our data supports the idea that our expectations of visual experiences are controlled by a feedback loop between the visual cortex and the medial temporal lobe,” said Dr. Zaghloul. “High frequency waves of neural activity appear to carry an error message when we see something that does not match our expectations, while the lower frequency waves may be updating our memories.”

Reference: Rafi U. Haque et al, Feedforward prediction error signals during episodic memory retrieval, Nature Communications (2020). DOI: 10.1038/s41467-020-19828-0

Provided by National Institutes of Health

Why Your Face Looks Different From a Chimp’s? (Biology)

The face: it’s personal, yet universal. It’s how we recognize each other and communicate our emotions—and yet there’s more to it than immediately meets the eye. Beneath the skin and muscles that form our smirks and scowls are 14 different bones that house parts of the digestive, respiratory, visual, and olfactory systems—enabling us to sniffle, chew, blink, and much more.

Thanks to the discovery of fossils, researchers are able to observe how faces have evolved over time, from extinct hominin species walking the Earth millions of years ago, to Neanderthals, to the only remaining hominin species—Homo sapiens, or humans. Analyzing the visages of our ancestors provides clues about why our faces have grown shorter and flatter over millennia. Which environmental and cultural factors influenced the structure of our modern faces, and how might climate change reshape them yet again?

Two years ago, Rodrigo Lacruz, associate professor of basic science and craniofacial biology at NYU College of Dentistry, gathered a group of leading human evolution experts at a conference in Madrid, Spain, to discuss the evolutionary roots of the modern human face. Their detailed account of its history—which appears April 15 in Nature Ecology & Evolution—covers roughly 4 million years and integrates many different lines of research, given the numerous factors that contribute to facial shape. The researchers conclude that the face’s appearance is a combination of biomechanical, physiological, and social influences.

NYU Dentistry’s Rodrigo Lacruz

NYU News asked Lacruz to describe how we came to look the way we do.

How does the human face differ from that of our predecessors—and our closest living relatives?

In broad terms, our faces are positioned below the forehead, and lack the forward projection that many of our fossil relatives had. We also have less prominent brow ridges, and our facial skeletons have more topography. Compared to our closest living relatives, the chimpanzees, our faces are more retracted and are integrated within the skull rather than being sort of pushed in front of it.

How has our diet played a role?

Diet has been considered as an important factor, especially when it comes to the mechanical properties of foods consumed—soft versus hard objects. For instance, some early hominins had bony structures that suggested the presence of powerful muscles for mastication, or chewing, and they had very large chewing teeth, indicating that they were likely adapted for processing harder objects. These fossils had unusually flat faces. In more recent humans, the transition from being hunter-gatherers to settlers also coincides with changes in the face, specifically the face becoming smaller. However, many of the details of this interaction between diet and facial shape are unclear because diet affects certain parts of the face more than others. This reflects how modular the face is.

A raised eyebrow, grimace, and squint all signal very different things. Did the human face evolve to enhance social communication?

We think that enhanced social communication was a likely outcome of the face becoming smaller, less robust, and with a less pronounced brow. This would have enabled more subtle gestures and hence enhanced non-verbal communication. Let’s consider chimpanzees, for example, which have a smaller repertoire of facial expressions compared to us, and a very different facial shape. The human face, as it evolved, likely gained other gestural components. Whether social communication by itself was the driver for facial evolution is much less likely.

Climate also plays a role in evolution. How have factors like temperature and humidity influenced the evolution of the face?

We see that perhaps more clearly in Neanderthals, which adapted to live in colder climates and had large nasal cavities. This would have enabled an increased capacity for warming and humidifying the air they inhaled. The expansion of the nasal cavity modified their faces by pushing them somewhat forward, which is more evident in the midface (around and below the nose). The likely ancestors of the Neanderthals, a group of fossils from the Sima de los Huesos site in Spain that also lived in somewhat colder conditions, also showed some expansion of the nasal cavity and a midface that jutted forward. While temperature and humidity affect the parts of the face involved in breathing, other areas of the face may be less impacted by climate.

In the Nature article, you mention that climate change could affect human physiology. How could a warming planet change our faces?

The nasal cavity and upper respiratory tract (the area at the back of the nose near the pharynx) influence the shape of the face. Part of this knowledge derives from studies in modern people by some of our collaborators. They have shown that the shape of the nasal cavity and nasopharynx differ between people living cold and dry climates and those in hot and humid climates. After all, the nose helps warm and humidify inhaled air before it reaches the lungs.

The expected rise in global temperatures could have an effect on human physiology—specifically, how we breathe—over time. The extent of these changes in the face will depend, among other things, on how much warmer it grows. But if predictions of a 4°C (~7°F) rise in temperatures are correct, changes in the nasal cavity might be anticipated. In these scenarios, we should also take into account the high mobility of gene flow, which is an important factor as well, so the effects of climate change can be difficult to predict.

References: Lacruz, R.S., Stringer, C.B., Kimbel, W.H. et al. The evolutionary history of the human face. Nat Ecol Evol 3, 726–736 (2019). https://doi.org/10.1038/s41559-019-0865-7

Provided by New York University

Women’s Hearts Age Differently (Medicine / Cardiology)

Cardiologist Catherine Gebhard’s research focuses on why certain diseases affect women and men differently. For the gender medicine pioneer, the corona pandemic is both a textbook example and a call for action at the same time.

To compensate for its smaller volume, the female heart pumps at a higher rate – which brings women no benefit, according to recent data. (Image: Christoph Fischer)

A coronavirus infection affects different people in different ways. The disparity is particularly evident between men and women. “When I saw the initial infection and death numbers, it was clear to me that we had to take action,” says cardiologist Catherine Gebhard, a specialist in gender medicine.

In Switzerland, as across the world, the number of men who die from Covid-19 is around 60 percent higher than women. In some nations, the number rises to three quarters. Men are more likely to be hospitalized, occupy more beds in the intensive care unit, and need more intensive and longer treatment. “The gender differences in the progression of the disease are significant,” says Gebhard. It is therefore important for doctors to discover the reasons for these disparities, since the best way of preventing and treating the disease depends on knowing where the differences come from.

Influence of sex hormones
To come to an understanding of the causes as quickly as possible, the cardiologist and her colleagues developed a study on the influence of sex and gender on the progression of Covid-19. The study was financed by the Swiss National Science Foundation as part of a special call for projects focused on coronavirus. “We assume that it is the impact of gender hormones on particular cell molecules and the differing immune responses between women and men that are chiefly responsible,” says Gebhard. These assumptions are based on well-founded hypotheses. For example, it is known that the female hormone estrogen affects molecules on the surface of the cells that the coronavirus needs to penetrate. The subject here is the membrane protein, ACE2, which can be found on the outer cell layers of the lung tissue and blood vessels that Sars-Cov-2 attacks.

Earlier studies have shown that the heart and kidney tissue in men is more densely covered with ACE2 than that of women. And initial evidence indicates that female and male sex hormones may have opposite effects on this protein. In her research, Gebhard examines the influence of estrogen on these receptor densities.

In the case of another membrane molecule, named Tmprss2, the male sexual hormone, testosterone, appears to play a role in influencing the receptors. This is indicated by preliminary successes from anti-testosterone treatments for Covid-19 conducted in Italy. Together, the two proteins form part of a larger and extremely complicated network of hormones and enzymes that regulate the volume of blood and water in the body. Investigations are twofold; some are carried out in labs using animal studies, others in clinics on patients. The University Hospital Zurich (USZ) as well as university clinics in Basel, Bern and Berlin are involved in the work. It is hoped, the researcher says, that initial results will be ready by the end of the year. The same goes for outcomes on the immune system from studies looking at gender-specific responses to inflammatory reactions.

Shrinking hearts

For Catherine Gebhard, the pandemic is a textbook example of the still little-known discipline of gender medicine. No specialist title exists here in Switzerland – in contrast to Austria, for example. Originating from Bad Säckingen am Rhein, the 42-year old doctor is a pioneer in the field, and in 2016 was appointed to the first professorship for gender medicine in Switzerland at UZH.

The turning point for her scientific career was a discovery by her former boss, head of echocardiography at the University Hospital Zurich. Here, where ultrasound equipment is used to visualize and measure the ventricles and valves of the heart, her mentor noticed that the hearts of older women beat more strongly than those of men of the same age. Gebhard then went on to prove in her own study that the female heart contracts more strongly and pumps more blood into the body’s system. “I haven’t been able to let the subject go ever since,” she says.

It has now been proven that women’s hearts age differently to those of men. “The female heart’s pumping function changes with age because women’s hearts grow smaller after the menopause, which is not the case with men,” says the cardiologist. To compensate for its smaller volume, the female heart pumps at a higher rate – which brings women no benefit, according to recent data. In fact, it raises female mortality levels – even though women contract diseases from constricted and occluded coronary arteries on average 10 years later than men. Before menopause, women are protected by estrogen, but after menopause, this protection wears away causing the volume of deposits in the blood vessels to grow, and with it the risk of a heart attack or stroke. The fact that women experience heart attacks differently to men is still far too little known. “Heart attacks are often not recognized quickly enough because symptoms differ,” says Gebhard. Instead of chest pain radiating into the left arm and lower jaw, women often have more inconspicuous complaints, such as abdominal and back pain or nausea. As a result, they go to the doctor later, which can be fatal. As far as prevention is concerned, women are less likely to be examined for a narrowing of the coronary arteries. And women are generally underrepresented in clinical cardiological studies. All this contributes to the fact that more women die of cardiovascular diseases in Europe than men.

Dominant men

Medicine, especially cardiology, is dominated by men. This goes some way to explaining the tunnel vision tendency. But gender medicine is more than simply the biological differences between the sexes. “Gender medicine looks not only at biological factors but also at cultural and social aspects,” says Gebhard. In the case of heart disease, for example, studies have shown that women suffer greater mental stress after a heart attack than men. They have more concerns and face tougher challenges with their double and multiple responsibilities at work and in the family. This has been demonstrated by studies on women with heart disease that examine the activity of the brain’s fear center, the area known as the amygdala, Gebhard explains.

These social reactions overshadow the biological factors that are supposed to protect women. “The socio-cultural gender can have an opposite effect from the biological gender,” says Gebhard. This can also be observed with Covid-19: After lockdown, more women were infected than men. The assumption is that they were more exposed to coronavirus at their workplace and in caring for family and relatives. In order to investigate these socio-cultural influences, certain doctors are already working with a “gender score” that builds these aspects into the treatment. Canada and Germany are leading the way in this respect.

Bias with consequences

Although gender medicine is enjoying greater understanding in Switzerland, research findings – especially in clinical medicine – are still too rarely applied, Gebhard regrets. And she continues to hear the accusation that gender medicine is biased towards women even though, with men affected more acutely, Covid-19 proves the exact opposite. This has led one colleague or another to comment: “At last you’re doing something for men.”

In reaction, the cardiologist can only smile. It has now been found that anorexia, for example, is not a typical women’s disease, as so often labelled. Men suffer from anorexia too, but the treatments are designed for female patients. Another example is osteoporosis – said to mainly afflict women after menopause. As a result, it is seriously underdiagnosed in men and is one of the most neglected disease patterns in Europe. Which all goes to prove that gender medicine is of benefit to men and women alike.

Provided by University Of Zurich

Remembering The Same Event Differently? Thats called “Roshomon Effect” (Psychology)

Have you ever left a party and immediately started recounting how rude the host was to you, only to have your friend look at you puzzled and recount the very same conversation—only with the host being warm and friendly? That’s an everyday version of the Rashomon effect, a phenomenon where different people have contradictory accounts of the same event.

It’s named after Akira Kurosawa’s 1950 film Rashomon, in which a samurai has been mysteriously killed. Four characters give conflicting reports of what happened: the samurai’s wife says she was raped by a bandit, fainted, then awoke to find the samurai dead; the bandit says he seduced the wife and then fought the samurai to an honorable death; the woodcutter says he witnessed the rape and murder but stayed out of it; and the dead samurai’s ghost says that he killed himself. The true question of Rashomon isn’t whose account is correct, however. Instead, it forces audiences to ask if there even is a correct version of events.

Of course, a real-world crime would certainly have a single true explanation. In reality, conflicting accounts come down to the unreliability of human memory. In fact, research has shown that implanting false memories can be as simple as asking someone to recount an event that didn’t happen. What’s more, every time you remember something, you rewrite it in your brain. If that recollection contains errors, you’ll strengthen those errors until you’re positive they’re correct. That’s why even a memory as extreme as fighting a samurai could be constructed out of thin air with the right kind of suggestion.

But about that last question: is there even a correct version of events? While the answer is usually yes, it’s sometimes no—especially in quantum mechanics. In that scientific realm, tiny particles live in superposition, where they’re in every possible state at once. They only take on a single state once they’re observed. So is that state the “correct” one, or are all of the states technically correct? It’s enough to make you really appreciate your macroscopic existence.