It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Tuesday, July 09, 2024
AJPH study shows that permit to purchase laws are a promising avenue to reduce suicides in young adults
Researchers find that implementing broader firearm access laws may be more effective than just age-based restriction
AMERICAN PUBLIC HEALTH ASSOCIATION
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RESEARCHERS HAVE FOUND THAT THE PERMIT TO PURCHASE LAWS ARE A MORE PROMISING AVENUE TO REDUCE YOUNG ADULT FIREARM SUICIDES THAN MINIMUM AGE RESTRICTIONS
In 2020, suicide ranked as the third leading cause of death for adults aged 18 to 20 years in the United States. Firearms were implicated in approximately half of these cases, and by 2017, they had surpassed motor vehicles as the leading cause of death in this age group. While ongoing debates on gun violence and mental health have increased public support for restricted firearm access, not much is known about the impact of gun control policies on young adults.
To fill this knowledge gap, a recent study published in the August issue of the American Journal of Public Healthon July 03, 2024, investigated the correlation between state firearm legislation and suicides in young adults aged 18 to 20 years. The study was led by Assistant Professor Emma E. Fridel who expresses her concern by saying, “Currently, there are no federal restrictions on buying long guns from private sellers or owning ammunition. [Also, no study] has examined how state minimum age laws affect the incidence of young adult suicide based on background check legislation.”
The study explains that state laws that impose minimum age restrictions primarily focus on regulating firearm purchases from private sellers. These restrictions are typically enforced through either universal background checks or permit to purchase (PTP) laws. PTP laws mandate that individuals must personally apply for a firearm permit before buying, involving local or state law enforcement agencies in the process. The authors analyzed the collective and individual effects of these firearm regulations across all 50 US states, from the year 1991 to 2020.
Looking at the individual impact of various laws, the study showed that state laws increasing the minimum handgun purchase age to 21 were associated with a 12% reduction in firearm suicides in people aged 18 to 20 years, without significantly affecting the overall suicide rate. In contrast, state PTP laws were associated with a significant reduction, with a 39% decrease in firearm suicides and a 14% decrease in the overall suicide rate among this age group.
However, the effects of minimum age restrictions were more pronounced in conjunction with other laws. In states with PTP laws, minimum age restrictions decreased firearm suicide by 33%, whereas in states without PTP laws, these restrictions had a negligible effect. This underscores the dependency of the protective effects of minimum age laws on the presence of the state PTP laws.
Interestingly, the results also indicated that states adopting both policies (minimum age restrictions and PTP laws) averaged fewer than 10 young adult firearm suicides per year. In contrast, states with only minimum age laws averaged 14 firearm suicides annually, and those without either policy averaged 16.
There are multiple reasons that PTP laws are particularly effective, and may even be lifesaving, for at-risk young adults. “Interacting face-to-face with law enforcement during the permitting process likely discourages underage buyers and increases the perceived risks for straw purchasers. Similarly, licensing fees and mandatory firearm safety–training classes may be cost prohibitive for unemployed or in-school young adults,” Dr. Fridel notes.
The PTP vetting procedures are also time-consuming, thus reducing the chances of impulsive suicide attempts. Dr. Fridel states “Approximately half of survivors of near-lethal suicide attempts deliberate for less than 10 minutes before acting, and some previous [research] suggests that younger individuals are more likely to impulsively attempt suicide.”
While age-based handgun restrictions may have minimal impact on young adult suicides, broader laws restricting overall firearm access could make a bigger difference. PTP laws are particularly vital in curbing access to lethal means for vulnerable young adults. With strong support from over three-quarters of Americans, PTP laws are poised as an effective, feasible policy to reduce firearm suicides based on evidence and public opinion.
In a nutshell, implementing comprehensive firearm access laws can greatly contribute to reducing suicides among young adults.
AJPH Study Shows That Permit to Purchase Laws Are a Promising Avenue to Reduce Suicides in Young Adults
It takes a cool microscope and antifreeze to really look at ice
KOBE UNIVERSITY
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“THROUGH VARIOUS TRIAL AND ERROR PROCESSES, WE FOUND THAT WE HAD TO COOL THE ENTIRE MICROSCOPE SYSTEM IN A COOLING BOX, AND IT TOOK SOME INGENUITY TO ENSURE THAT THE ATOMIC FORCE MICROSCOPE, A PRECISION MEASURING INSTRUMENT, COULD OPERATE STABLY AT SUB-ZERO TEMPERATURES,” EXPLAINS ONISHI HIROSHI.
Ice in nature is surrounded by liquid most of the time, and therefore it is key to understand how ice and liquid interact. A Kobe University and Institute for Molecular Science study could now for the first time directly observe the precise shape of ice at the interface between ice and liquid – by using antifreeze and a refrigerated microscope.
When we slide on ice, when snowflakes form, when we lick ice cream, the surface of the ice is always covered with liquid water, and understanding the interaction between the liquid water and the ice is vital to understanding the whole phenomenon. However, because ice and water quickly transform into each other, it has been impossible to directly observe the interface between the two.
To get closer to understanding how ice interacts with its surrounding liquid, researchers led by Kobe University’s ONISHI Hiroshi decided to try the next best thing. He says: “We came up with the idea of measuring ice immersed in antifreeze colder than 0°C. This way, the ice doesn’t melt and the interface doesn’t move, and it should be possible to make precise observations.” Even so, the researchers struggled to get good measurements of the ice. “Through various trial and error processes, we found that we had to cool the entire microscope system in a cooling box, and it took some ingenuity to ensure that the atomic force microscope, a precision measuring instrument, could operate stably at sub-zero temperatures,” explains the Kobe University researcher.
In The Journal of Chemical Physics, the group now published their results. They found that, while ice without surrounding liquid features so-called “frost pillars” about 20 nanometers tall, in antifreeze the ice is perfectly flat with occasional steps only one molecular layer high. “We think that the flat surface is formed through … partial dissolution and recrystallization of the ice surface in the 1-octanol liquid (the antifreeze),” the researchers write in the paper.
Onishi and his team also tried different liquids, all alcohols like 1-octanol. And even though all liquids they tried have similar properties, they observed that the ice surface looks different in each case, underscoring the importance of directly measuring the interface. In addition, they investigated the “hardness” of the ice surface under 1-octanol and found that the ice is much harder than previously estimated using less direct methods.
The researchers hope that their results will invite further study of the ice-liquid interface, but they have also set clear goals for their own future work saying: “We expect to increase the resolution of the microscope to single water molecules and use measurement methods other than atomic force microscopy. In this way, we hope to expand the range of possible applications of molecular-level measurements of the ice-antifreeze interface.”
This research was funded by the Ministry of Education, Culture, Sports, Science and Technology Japan (grants JPMXP1222MS0008 and JPMXP1223MS0001) and the Japan Society for the Promotion of Science (grants 21K18935 and 23H05448). It was conducted in collaboration with researchers from the Institute for Molecular Science, National Institutes of Natural Sciences.
Kobe University is a national university with roots dating back to the Kobe Commercial School founded in 1902. It is now one of Japan’s leading comprehensive research universities with nearly 16,000 students and nearly 1,700 faculty in 10 faculties and schools and 15 graduate schools. Combining the social and natural sciences to cultivate leaders with an interdisciplinary perspective, Kobe University creates knowledge and fosters innovation to address society’s challenges.
Onishi-Ice_interface-Micrograph
While ice without surrounding liquid (A) features so-called “frost pillars” about 20 nanometers tall, in 1-octanol antifreeze (B) the ice is perfectly flat with occasional steps only one molecular layer high. In different liquids (C: 1-hexanol. D: 1-butanol) with similar properties, the ice surface looks different in each case, underscoring the importance of directly measuring the interface.
THE KEY LARGO TREE CACTUS WAS INITIALLY FOUND GROWING IN THE UNITED STATES IN 1992 AT A SINGLE SITE. THAT POPULATION HAS SINCE BEEN LOST TO A COMBINATION OF RISING SEA LEVELS AND INCREASINGLY INTENSE STORMS.
The United States has lost its only stand of the massive Key Largo tree cactus in what researchers believe is the first local extinction of a species caused by sea level rise in the country.
The Key Largo tree cactus (Pilosocereus millspaughii) still grows on a few scattered islands in the Caribbean, including northern Cuba and parts of the Bahamas. In the United States, it was restricted to a single population in the Florida Keys, first discovered in 1992 and monitored intermittently since.
Salt water intrusion from rising seas, soil depletion from hurricanes and high tides, and herbivory by mammals had put significant pressure on the population. By 2021, what had been a thriving stand of about 150 stems was reduced to six ailing fragments, which researchers salvaged for off-site cultivation to ensure their survival.
“Unfortunately, the Key Largo tree cactus may be a bellwether for how other low-lying coastal plants will respond to climate change,” said Jennifer Possley, director of regional conservation at Fairchild Tropical Botanic Garden and lead author on a study published Tuesday, July 9 that documents the population’s decline.
Two closely related cacti negatively affected by environmental change
Comparatively little is known about Florida’s rare cacti. Researchers initially stumbled upon the Key Largo tree cactus in an isolated mangrove forest, and for several years afterward, its identity remained uncertain. Most considered it to be a unique population of the similarly named Key tree cactus (Pilosocereus robinii), a federally endangered species that is present elsewhere in the Florida Keys.
The two cacti have a similar appearance. The stems of both shoot up perpendicular to the ground and can grow to be more than 20 feet tall. Both have cream-colored flowers that smell like garlic and reflect moonlight, attracting bat pollinators, while their bright red and purple fruit catch the eye of birds and mammals.
But there are key differences as well, which made Alan Franck, currently the herbarium collection manager at the Florida Museum of Natural History, suspect they were dealing with something unique on Key Largo.
“The most striking difference is the tuft of long, woolly hairs at the base of the flowers and fruits,” Franck said. The hair is so thick, it can look as though the cactus is covered in drifts of snow. Spines of the Key Largo cactus are also twice as long as they are on the Key tree cactus.
In 2019, Franck confirmed that the Key Largo population was the first and only known instance of Pilosocereus millspaughii in the U.S.
By then, it was succumbing to some of the same environmental pressures that had plagued its relative, the Key tree cactus, over the last century. The latter was once common throughout the Florida Keys, but its numbers dipped dangerously low as more people moved to the area.
Writing in 1917, botanist John Small noted that the Key tree cactus “was for a long time very abundant [on Key West]…In recent years, with the destruction of the hammock for securing firewood and for developing building sites, this interesting cactus has become scarce, until at present it is on the verge of extermination in its natural habitat.”
The Key tree cactus was listed as federally endangered in 1984, but its numbers continued to wane. Between 1994 and 2007, it decreased by 84%.
Researchers at Fairchild began monitoring all of the tree cactus populations annually in 2007, working in tandem with local land managers. One Fairchild-led study showed that salt levels were higher in soil beneath dead vs. living cacti in the years following a storm surge event in the Lower Keys, drawing a clear connection between mortality and increased salinity.
Researchers also initiated a robust conservation collection for these species. Potted cacti are grown at a facility in Coral Gables, Florida, and seeds from both wild and cultivated plants are carefully banked for long-term conservation.
Researchers study and rescue the remnants of a dwindling stock
The Key Largo tree cactus grew on a low limestone outcrop surrounded by mangroves near the shore. The site originally had a distinct layer of soil and organic matter that allowed the cactus and other plants to grow, but storm surge from hurricanes and exceptionally high tides eroded away this material until there wasn’t much left.
Salt-tolerant plants that had been previously restricted to brackish soils beneath the mangroves slowly began creeping up the outcrop, an indication that salt levels were increasing.
Given enough time, these changing conditions would likely have killed the cactus. But other incidents occurred that hastened the pace.
“We noticed the first big problem in 2015,” said study co-author James Lange, a research botanist at Fairchild. When he and his colleagues arrived to evaluate the plants that year, half of the cacti had died, apparently as a result of an alarming amount of herbivory. Cacti store reserves of water in their succulent stems, which allows them to survive for long periods of time without rain. This makes them enticing to animals when other sources of water are scarce.
“In 2011, we started seeing saltwater flooding from king tides in the area,” Lange said, referring to particularly high ocean tides. “That limits the amount of freshwater available to small mammals and might be related to why the herbivores targeted this cactus, but we can’t say for sure. We’d never seen cactus herbivory like this anywhere in the Lower Keys, where flooding has tended to be less extensive.”
The team set out cameras in hopes of finding the culprit, but whatever it was did not return, and there was no evidence of significant herbivory thereafter. Yet, when the team came back the following year, roughly another 50% of the population had died. In response, staff from Fairchild and the Florida Department of Environmental Protection took a few cuttings of what remained to grow in greenhouses.
In 2017, category 5 Hurricane Irma swept across South Florida, creating a 5-foot storm surge. The highest point on Key Largo is only 15 feet above sea level, and large portions of the island remained flooded for days afterward. Once the storm had passed, the Fairchild team conducted triage with several cactus populations throughout the Keys, removing branches that had fallen on cacti and salvaging other ill-fated material. Conditions were so extreme that biologists had to put out kiddie pools of freshwater to keep local wildlife alive.
Exacerbating the already degrading Key Largo tree cactus habitat, king tides in 2019 left large portions of the island, including the extremely low-lying outcrop, flooded for over three months.
By 2021, there were only six Key Largo tree cactus stems left. As it was clear the population wasn’t going to survive, the team allowed the plants to flower and fruit for the remainder of the year, then salvaged all remaining green material and replanted it in greenhouses or controlled settings outdoors. At present, researchers know of no naturally growing Key Largo cacti in the United States.
“We have tentative plans with the Florida Department of Environmental Protection to replant some in the wild,” Possley said.
Similar efforts are responsible, in large part, for the continued existence of the related Key tree cactus in Florida. “The amount of reintroduced material of this species is already more than the amount of wild material that’s left,” Possley said.
But, she added, this may end up being more of a stopgap than a solution. Environments suitable for tree cacti are disappearing along with the plants they support. “It’s generally a fringe between the mangroves and upland hammocks called thorn scrub, and there just aren’t many places like that left where we can put reintroduced populations.”
The decline of the Key Largo tree cactus and the necessity of its removal has given researchers an idea of what to expect in the future as species contend with a rapidly warming world. Instead of a smooth, predictable rise in sea or salt levels, the reality of climate change is messier and manifests itself in a complex series of related events that put additional pressure on species that are already stressed.
“We are on the front lines of biodiversity loss,” said study co-author George Gann, executive director for the Institute for Regional Conservation. “Our research in South Florida over the past 25 years shows that more than one-in-four native plant species are critically threatened with regional extinction or are already extirpated due to habitat loss, over collecting, invasive species and other drivers of degradation. More than 50 are already gone, including four global extinctions.”
The authors published their study in the Journal of the Botanical Research Institute of Texas.
Staff from Fairchild and the Florida Department of Environmental Protection removed all remaining green material in 2021 after it became clear the population was not going to survive.
CREDIT
Photo courtesy of Jennifer Possley
Image 3 (IMAGE)
FLORIDA MUSEUM OF NATURAL HISTORY
The Key Largo tree cactus can grow to impressive heights.
CREDIT
Photo courtesy of Susan Kolterman
JOURNAL
Journal of the Botanical Research Institute of Texas
First U.S. vascular plant extirpation linked to sea level rise? Pilosocereus millspaughii (Cactaceae) in the Florida Keys, U.S.A.
ARTICLE PUBLICATION DATE
9-Jul-2024
Disclaimer: AAAS and
A time crystal made of giant atoms
Researchers from TU Wien (Vienna, Austria) and Tsinghua University (Beijing, China) have created an extremely exotic state of matter. Its atoms have a diameter a hundred times larger than usual
VIENNA UNIVERSITY OF TECHNOLOGY
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A RYDBERG ATOM HAS AN ELECTRON WHICH IS FAR AWAY FROM THE NUCLEUS
A crystal is an arrangement of atoms that repeats itself in space, in regular intervals: At every point, the crystal looks exactly the same. In 2012, Nobel Prize winner Frank Wilczek raised the question: Could there also be a time crystal – an object that repeats itself not in space but in time? And could it be possible that a periodic rhythm emerges, even though no specific rhythm is imposed on the system and the interaction between the particles is completely independent of time?
For years, Frank Wilczek's idea has caused much controversy. Some considered time crystals to be impossible in principle, while others tried to find loopholes and realise time crystals under certain special conditions. Now, a particularly spectacular kind of time crystal has successfully been created at Tsinghua University in China, with the support from TU Wien in Austria. The team used laser light and very special types of atoms, namely Rydberg atoms, with a diameter that is several hundred times larger than normal. The results have now been published in the journal "Nature Physics".
Spontaneous symmetry breaking
The ticking of a clock is also an example of a temporally periodic movement. However, it does not happen by itself: Someone must have wound the clock and started it at a certain time. This starting time then determined the timing of the ticks. It is different with a time crystal: according to Wilczek's idea, a periodicity should arise spontaneously, although there is actually no physical difference between different points in time.
"The tick frequency is predetermined by the physical properties of the system, but the times at which the tick occurs are completely random; this is known as spontaneous symmetry breaking," explains Prof Thomas Pohl from the Institute of Theoretical Physics at TU Wien.
Thomas Pohl was in charge of the theoretical part of the research work that has now led to the discovery of a time crystal at Tsinghua University in China: Laser light was shone into a glass container filled with a gas of rubidium atoms. The strength of the light signal that arrived at the other end of the container was measured.
"This is actually a static experiment in which no specific rhythm is imposed on the system," says Thomas Pohl. "The interactions between light and atoms are always the same, the laser beam has a constant intensity. But surprisingly, it turned out that the intensity that arrives at the other end of the glass cell begins to oscillate in highly regular patterns."
Giant atoms
The key to the experiment was to prepare the atoms in a special way: The electrons of an atom can orbit the nucleus on different paths, depending on how much energy they have. If energy is added to the outermost electron of an atom, its distance from the atomic nucleus can become very large. In extreme cases, it can be several hundred times further away from the nucleus than usual. In this way, atoms with a giant electron shell are created – so-called Rydberg atoms.
"If the atoms in our glass container are prepared in such Rydberg states and their diameter becomes huge, then the forces between these atoms also become very large," explains Thomas Pohl. "And that in turn changes the way they interact with the laser. If you choose laser light in such a way that it can excite two different Rydberg states in each atom at the same time, then a feedback loop is generated that causes spontaneous oscillations between the two atomic states. This in turn also leads to oscillating light absorption." All by themselves, the giant atoms stumble into a regular beat, and this beat is translated into the rhythm of the light intensity that arrives at the end of the glass container.
"We have created a new system here that provides a powerful platform for deepening our understanding of the time crystal phenomenon in a way that comes very close to Frank Wilczek's original idea," says Thomas Pohl. "Precise, selfsustained oscillations could be used for sensors, for example. Giant atoms with Rydberg states have already been successfully used for such techniques in other contexts."
A static system with a continuous input of light leads to time-dependent periodic signals.
Dissipative time crystal in a strongly interacting Rydberg gas
Egg cell maintenance: Long-lived proteins may be essential
Max Planck researchers have discovered that extremely long-lived proteins in the ovary may keep mammalian egg cells healthy and preserve fertility for a long time
MAX-PLANCK-GESELLSCHAFT
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FEMALE MAMMALS ARE BORN WITH ALL THE EGG CELLS THEY WILL EVER HAVE IN THEIR OVARIES. SOME OF THESE CELLS THEREFORE LIVE FOR A LONG TIME – AND MUST REMAIN FUNCTIONAL THROUGHOUT THIS PERIOD. EXPERIMENTS WITH MICE HAVE NOW SHOWN: EXTREMELY LONG-LIVED PROTEINS IN THE OVARY CAN KEEP EGG CELLS HEALTHY AND PRESERVE FERTILITY FOR A LONG TIME. IN THE MOUSE EGG CELL SHOWN HERE, THE CHROMOSOMES ARE STAINED MAGENTA AND THE CYTOSKELETAL PROTEIN ACTIN IS STAINED BLUE AND WHITE.
CREDIT: MELINA SCHUH / MAX PLANCK INSTITUTE FOR MULTIDISCIPLINARY SCIENCES
Female mammals – including humans – are born with all of their egg cells. Of a woman’s one to two million egg cells, about 400 mature before menopause and can be fertilized. Some egg cells therefore survive for several decades – and need to remain functional over this long time. Extremely long-lived proteins in the ovary seem to play an important role in this, as teams of researchers from Göttingen (Germany) have now discovered in experiments with mice. These long-lived proteins appear to help maintain fertility for as long as possible.
“Egg cells need to be preserved throughout a woman’s reproductive life so they can develop into healthy embryos,” explains Melina Schuh, Director at the Max Planck Institute (MPI) for Multidisciplinary Sciences. Even in mice, which can only reproduce for just over a year, the lifespan of egg cells is much longer than the average lifespan of proteins. Living cells recycle most of their proteins within just a few days. However, depending on the cell type and function, not all of the proteins are degraded at the same rate.
Many extremely long-lived proteins in ovaries
Together with teams led by group leaders Juliane Liepe and Henning Urlaub, Schuh’s team has now quantitatively investigated how frequently long-lived proteins occur in the ovaries. For their experiments, the researchers combined various biochemical and molecular methods with mathematical modeling. “This multidisciplinary approach allowed us to observe proteins in the ovaries and oocytes of mice at different stages in life to determine the age of the proteins,” says Max Planck research group leader Liepe. The scientists also analyzed how the proteins’ abundance changed over time by recording an ovary protein inventory of nearly 8,900 proteins.
The result: Ovaries contain an extremely high number of long-lived proteins – more than other tissues, and even more than the brain. These stable proteins are found not only in the eggs themselves but also in other somatic cells in the ovary.
“Many of the long-lived proteins have protective functions, such as repairing DNA or protecting cells from damage,” explains Urlaub, who is a group leader at the MPI and the University Medical Center Göttingen (UMG). These molecular folding helpers, known as chaperones, prevent misfolded proteins from aggregating and disrupting cellular processes. The experiments of the Göttingen scientists showed that the chaperones are extremely stable in the ovary and prevent aggregation for a longer time than in the brain, for example. Similarly, the egg cell’s powerhouses – the mitochondria – contained particularly stable proteins. Since mitochondria are passed on from mother to offspring, it is essential that these organelles stay healthy.
Fewer long-lived proteins with age
“However, the concentration of many long-lived proteins in the ovary and egg cells decreases with age. In contrast, proteins associated with acute inflammation or immune response increase over time,” Schuh reports. This is in line with previous findings that inflammatory reactions are more frequent in the ovaries of older women. “The complex ovarian protein network changes. The gradual disappearance of long-lived proteins from the ovaries and egg cells may explain why fertility declines in female mammals after a certain age.”
The study was funded by the Cluster of Excellence “Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells” (MBExC), of which Melina Schuh and Henning Urlaub are members.
The maintenance of oocytes in the mammalian ovary involves extreme protein longevity
Run screaming or slow retreat? New study advances understanding of brain responses to emotionally-charged scenes
TRINITY COLLEGE DUBLIN
The ability to recognise and respond to emotionally-charged situations is essential to a species’ evolutionary success. A new study published today [July 9th] in Nature Communications advances our understanding of how the brain responds to emotionally charged objects and scenes.
The research, led by Trinity College Dublin neuroscientist Prof. Sonia Bishop and Google researcher Samy Abdel-Ghaffar while he was a PhD student in Prof. Bishop's lab at UC Berkeley, has identified how the brain represents different categories of emotional stimuli in a way that allows for more than a simple 'approach avoid' dichotomy when guiding behavioural responses. The research was funded by the National Institutes of Health, USA.
Sonia Bishop, now Chair of Psychology, in Trinity’s School of Psychology and senior author of the paper explains: “It is hugely important for all species to be able to recognise and respond appropriately to emotionally salient stimuli, whether that means not eating rotten food, running from a bear, approaching an attractive person in a bar or comforting a tearful child.
“How the brain enables us to respond in a nuanced way to emotionally-charged situations and stimuli has long been of interest. But, little is known about the how the brain stores schemas or neural representations to support the nuanced behavioural choices we make in response to emotional natural stimuli.
“Neuroscience studies of motivated behaviour often focus on simple approach or avoidance behaviours – such as lever pressing for food or changing locations to avoid a shock. However, when faced with natural emotional stimuli, humans don’t simply choose between ‘approach’ or ‘avoid’. Rather they select from a complex range of suitable responses. So, for example, our ‘avoid’ response to a large bear (leave the area ASAP) is different to our ‘avoid’ response to a weak, diseased, animal (don’t get too close). Similarly our ‘approach’ response to the positive stimuli of a potential mate differs to our ‘approach’ reaction to a cute baby.
“Our research reveals that the occipital temporal cortex is tuned not only to different categories of stimuli but it also breaks down these categories based on their emotional characteristics in a way that is well suited to guide selection between alternate behaviours.”
The research team from Trinity College Dublin, University of California Berkeley, University of Texas at Austin, Google and University of Nevada Reno, analysed the brain activity of a small group of volunteers when viewing over 1,500 images depicting natural emotional scenes such as a couple hugging, an injured person in a hospital bed, a luxurious home, and an aggressive dog.
Participants were asked to categorise the images as positive, negative or neutral and to also rate the emotional intensity of the images. A second group of participants picked the behavioural responses that best matched each scene.
Using cutting-edge modelling of brain activity divided into tiny cubes (of under 3mm3) the study discovered that the occipital temporal cortex (OTC), a region at the back of the brain, is tuned to represent both the type of stimulus (single human, couple, crowd, reptile, mammal, food, object, building, landscape etc.) and the emotional characteristics of the stimulus – whether it’s negative, positive or neutral and also whether it’s high or low in emotional intensity.
Machine learning showed that these stable tuning patterns were more efficient in predicting the behaviours matched to the images by the second group of participants than could be achieved by applying machine learning directly to image features — suggesting that the OTC efficiently extracts and represents the information needed to guide behaviour.
Samy Abdel-Ghaffar, Google, commented: “For this project we used Voxel-Wise Modeling, which combines machine learning methods, large datasets and encoding models, to give us a much more fine-grained understanding of what each part of the OTC represents than traditional neuroimaging methods. This approach let us explore the intertwined representation of categorical and emotional scene features, and opened the door to novel understanding of how OTC representations predict behaviour."
Prof. Bishop added: "These findings expand our knowledge of how the human brain represents emotional natural stimuli. In addition, the paradigm used does not involve a complex task making this approach suitable in the future, for example, to further understanding of how individuals with a range of neurological and psychiatric conditions differ in processing emotional natural stimuli.”
Notes to editor:
The paper, “Occipital-temporal cortical tuning to semantic and affective features of natural images predicts associated behavioral responses” by Samy A. Abdel-Ghaffar, Alexander G. Huth, Mark D. Lescroart, Dustin Stansbury, Jack L. Gallant & Sonia J. Bishop, is available on request.
More about the study method:
The team used a novel large dataset of 1,620 emotional natural images and conducted functional magnetic resonance imaging with adult human volunteers, acquiring over 3,800 3D pictures of brain activity while participants viewed these images. Participants judged these images on valence (positive, negative or neutral) and arousal (or emotional intensity).
Modelling this data using small 2.4x2.4x3mm chunks or 'voxels' of brain activity, the researchers found that regions of occipital temporal cortex, in the back of the brain, showed differential representation of both stimulus semantic category and affective value. For example, positive high arousal faces were represented in slightly different regions to negative high arousal faces and neutral low arousal faces.
Furthermore, when a completely new set of participants were asked to select behaviours that went with each image, the top dimensions of this neural coding representational 'space' better predicted the behaviours selected than the top dimensions based directly on image features (for example is the stimulus animate? positive?). This suggests that the brain chooses which information is important or not important to represent and hold stable representations of sub-categories of animate and inanimate stimuli that integrate affective information and are optimally organised to support the selection of behaviours to different types of emotional natural stimuli.
