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By BENEDICT CAREY The brain damage was so severe that scientists all but gasped. Aaron Hernandez, the former New England Patriots tight end, was convicted of murder and killed himself in prison last April at age 27. An autopsy revealed that he had brain injuries akin to that seen in afflicted former players in their 60s, researchers announced on Thursday. The sheer extent of the damage turns on its head the usual question about violence and so-called chronic traumatic encephalopathy. If accumulated head trauma can cause such damage, might the injuries in turn lead to murder and suicide? It’s a natural presumption to make, given the tragic suicides of Junior Seau, Dave Duerson and other former football players diagnosed post-mortem with C.T.E. And it’s a question that the courts will have to wrestle with. On Friday, the National Football League vowed to defend itself against a lawsuit filed on behalf of Mr. Hernandez’s daughter and fiancée, who claims that his injuries and death were a direct result of his participation in football. The science itself — like most attempts to link brain biology to behavior — is murkier. In recent decades, researchers have made extraordinary strides in understanding the workings of brain cells, neural circuits and anatomy. Yet drawing a direct line from those basic findings to what people do out in the world is dicey, given the ineffable interplay between circumstance, relationships and personality. What scientists — from such diverse fields as psychiatry, neurology and substance use — can say is that the arrows seem to be pointing in the same direction. A number of brain states raise the risk of acting out violently, and the evidence so far, while incomplete, suggests that C.T.E. may be one of them. Dr. Samuel Gandy, director of the N.F.L. neurology program at Mount Sinai Medical Center, said that rage and irritability “are far and away the most prominent symptoms” among former players with likely C.T.E., in his research. His group has identified 10 of 24 former players who probably have C.T.E. © 2017 The New York Times Company

Keyword: Brain Injury/Concussion; Aggression
Link ID: 24104 - Posted: 09.23.2017

Tina Hesman Saey A genetic risk factor for Alzheimer’s disease is a double, make that triple, whammy. In addition to speeding up the development of brain plaques associated with Alzheimer’s, a gene variant known as APOE4 also makes tau tangles — another signature of the disease — worse, researchers report online September 20 in Nature. APOE4 protein also ramps up brain inflammation that kills brain cells, neuroscientist David Holtzman of Washington University School of Medicine in St. Louis and colleagues have discovered. “This paper is a tour de force,” says Robert Vassar, a neuroscientist at Northwestern University Feinberg School of Medicine in Chicago. “It’s a seminal study that’s going to be a landmark in the field” of Alzheimer’s research, Vassar predicts. For more than 20 years, researchers have known that people who carry the E4 version of the APOE gene are at increased risk of developing Alzheimer’s. A version of the gene called APOE3 has no effect on Alzheimer’s risk, whereas the APOE2 version protects against the disease. Molecular details for how APOE protein, which helps clear cholesterol from the body, affects brain cells are not understood. But Holtzman and other researchers previously demonstrated that plaques of amyloid-beta protein build up faster in the brains of APOE4 carriers (SN: 7/30/11, p. 9). Having A-beta plaques isn’t enough to cause the disease, Holtzman says. Tangles of another protein called tau are also required. Once tau tangles accumulate, brain cells begin to die and people develop dementia. In a series of new experiments, Holtzman and colleagues now show, for the first time, that there’s also a link between APOE4 and tau tangles. |© Society for Science & the Public 2000 - 2017.

Keyword: Alzheimers
Link ID: 24103 - Posted: 09.23.2017

By Ruth Williams Contrary to the longstanding belief that puberty is largely controlled by hormones, new evidence shows that sexual touch is a powerful puberty promoter. Touching prepubescent female rats’ genitals can cause the brain region that responds to such tactile stimuli to double in size and their bodies to show signs of puberty up to three weeks earlier than non-stimulated females, according to a report in PLOS Biology today (September 21). The study reveals the hitherto unappreciated influence of physical sexual experience on the young brain and body. “The dominant idea has been that puberty is controlled in the brain and in behavior by the release of hormones . . . but there has been a smattering of findings over the years that additional environmental influences effect puberty and the onset of sexual behavior,” says Dan Feldman of the University of California, Berkeley, who was not involved in the study. This new work “suggests that maybe this is true and that actual tactile stimulation can be something that accelerates the onset of puberty,” he adds. Puberty in mammals is a period of dramatic changes not just to the body, but to behavior and brain function. Indeed, one of the most pronounced changes, recently observed in both male and female rats, is the doubling in size of the genital cortex, which is a part of the larger somatosensory cortex—the brain area associated with physical sensation. © 1986-2017 The Scientist

Keyword: Sexual Behavior; Development of the Brain
Link ID: 24102 - Posted: 09.23.2017

By NATALIE ANGIER Tom Vaughan, a photographer then living in Colorado’s Mancos Valley, kept a hummingbird feeder outside his house. One morning, he stepped through the portico door and noticed a black-chinned hummingbird dangling from the side of the red plastic feeder like a stray Christmas ornament. At first, Mr. Vaughan thought he knew what was going on. “I’d previously seen a hummingbird in a state of torpor,” he said, “when it was hanging straight down by its feet, regenerating its batteries, before dropping down and flying off.” On closer inspection, Mr. Vaughan saw that the hummingbird was hanging not by its feet but by its head. And forget about jumping its batteries: the bird was in the grip of a three-inch-long green praying mantis. The mantis was clinging with its back legs to the rim of the feeder, holding its feathered catch in its powerful, seemingly reverent front legs, and methodically chewing through the hummingbird’s skull to get at the nutritious brain tissue within. “It was staring at me as it fed,” Mr. Vaughan said. “Of course, I took a picture of it.” Startled by the clicking shutter, the mantis dropped its partially decapitated meal, crawled under the feeder — and began menacing two hummingbirds on the other side. “Talk about cognitive dissonance,” Mr. Vaughan said. “I always thought of mantises as wonderful things to have in your garden to get rid of bugs, but it turns out they sometimes go for larger prey, too.” “It gave me new respect for mantises,” he added. © 2017 The New York Times Company

Keyword: Aggression
Link ID: 24101 - Posted: 09.23.2017

By Anna Azvolinsky To define human consciousness at the neuronal level is among the most difficult of tasks for neuroscience. Still, researchers have made inroads, most recently by sinking electrodes deep with the brains of epilepsy patients and recording the activity of single neurons as the awake patients described whether they observed an image flashed before them. Previous work had found that the stronger the individual neuron activity, the more likely it is to be associated with conscious perception. In this latest study, published today (September 21) in Current Biology, researchers from the University of Bonn Medical Center in Germany find a second factor—timing—that appears important to the brain’s conscious awareness. Firing of single neurons within the medial temporal lobe (MTL), which is important for long-term memory, was weaker and delayed when human subjects were not aware of seeing an image compared to when they reported seeing one. “[The authors] contribute a major piece of the puzzle of human consciousness with a set of data that is very impressive,” says Rafael Malach, a neurobiologist who studies the human brain at the Weizmann Institute of Science in Israel and who was not involved in the work. “This is a well-designed study done in a medical setting that generated a unique dataset that is not easy to obtain,” says Itzhak Fried, a professor of neurosurgery at the Geffen School of Medicine at the University of California, Los Angeles, who was also not involved in the work but who has previously collaborated with one of the study’s authors, Florian Mormann. © 1986-2017 The Scientist

Keyword: Consciousness
Link ID: 24100 - Posted: 09.23.2017

By Neuroskeptic A new paper asks why neuroscience hasn’t had more “impact on our daily lives.” The article, Neuroscience and everyday life: facing the translation problem, comes from Dutch researchers Jolien C. Francken and Marc Slors. It’s a thought-provoking piece, but it left me feeling that the authors are expecting too much from neuroscience. I don’t think insights from neuroscience are likely to change our lives any time soon. Francken and Slors describe a disconnect between neuroscience research and everyday life, which they dub the ‘translation problem’. The root of the problem, they say, is that while neuroscience uses words drawn from everyday experience – ‘lying’, ‘love’, ‘memory’, and so on – neuroscientists rarely use these terms in the usual sense. Instead, neuroscientists will study particular aspects of the phenomena in question, using particular (often highly artificial) experimental tasks. As a result, say Francken and Slors, the neuroscience of (say) ‘love’ does not directly relate to ‘love’ as the average person would use the word: We should be cautious in interpreting the outcomes of neuroscience experiments simply as, say, results about ‘lying ’, ‘free will ’, ‘love’, or any other folk-psychological category. How then can neuroscientific findings be translated in terms that speak to our practical concerns in a nonmisleading, non-naive way? They go on to discuss the nature of the translation problem in much more detail, as well as potential solutions.

Keyword: Miscellaneous
Link ID: 24099 - Posted: 09.23.2017

By Ann Gibbons Neandertals have long been seen as the James Deans of human evolution—they grew up fast, died young, and became legends. But now, a rare skeleton of a Neandertal child suggests that our closest cousins didn’t all lead such fast lives—and that our own long childhoods aren’t unique. The find may reveal how Neandertals, like humans, had enough energy to grow bigger brains. “We like the paper because it puts the idea of ‘Neanderthal exceptionalism’ to rest,” wrote anthropologist Marcia Ponce de León and neurobiologist Christoph Zollikofer from the University of Zurich in Switzerland (who are not authors of the new study) in an email. “RIP.” Researchers have long known that modern humans take almost twice as long as chimpanzees to reach adulthood and have wondered when and why our ancestors evolved the ability to prolong childhood and delay reproduction. Our distant ancestors, such as the famous fossil Lucy and other australopithecines, matured quickly and died young like chimps. Even early members of our own genus Homo, such as the 1.6-million-year-old skeleton of an H. erectus boy, grew up faster than we do. By providing your email address, you agree to send your email address to the publication. Information provided here is subject to Science's Privacy Policy. But by the time the earliest known members of our species, H. sapiens, were alive 300,000 years ago at Jebel Irhoud in Morocco, they were taking longer to grow up. A leading theory is that big brains are so metabolically expensive that humans have to delay the age of reproduction—and, hence, have longer childhoods—so first-time mothers are older and, thus, bigger and strong enough to have the energy to feed babies with such big brains after birth when their brains are doubling in size. © 2017 American Association for the Advancement of Science

Keyword: Evolution; Development of the Brain
Link ID: 24098 - Posted: 09.22.2017

By STEPH YIN Worms and fish do it. Birds and bees do it. But do jellyfish fall asleep? It seems like a simple question, but answering it required a multistep investigation by a trio of Caltech graduate students. Their answer, published Thursday in Current Biology, is that at least one group of jellyfish called Cassiopea, or the upside-down jellyfish, does snooze. The finding is the first documented example of sleep in an animal with a diffuse nerve net, a system of neurons that are spread throughout an organism and not organized around a brain. It challenges the common notion that sleep requires a brain. It also suggests sleep could be an ancient behavior because the group that includes jellyfish branched off from the last common ancestor of most living animals early on in evolution. Working together was natural for Claire Bedbrook, Michael Abrams and Ravi Nath. The three leading co-authors of the paper are all Ph.D. candidates in biology at the California Institute of Technology and close friends. The project started with an observation by Mr. Abrams that some upside-down jellyfish in his lab would immediately slow their pulsing when the lights were turned off. Over coffee one evening, he discussed this phenomenon with Mr. Nath, who had been studying sleep in roundworms and pondering whether other “simple” animals slept. The two decided to visit Mr. Abrams’s lab in the middle of the night, to see how the jellyfish were behaving. The Cassiopea, or upside-down, jellyfish, demonstrated patterns of behavior consistent with sleep, according to an experiment conducted by Caltech graduate students. Credit Jan Easter Photography In the darkened lab, they observed a tankful of jellyfish pulsing infrequently and staying still for long periods of time — jellyfish that looked, in other words, like they were sleeping. Ms. Bedbrook started to believe they were onto something. © 2017 The New York Times Company

Keyword: Sleep; Evolution
Link ID: 24097 - Posted: 09.22.2017

Carrie Arnold The purpose and evolutionary origins of sleep are among the biggest mysteries in neuroscience. Every complex animal, from the humblest fruit fly to the largest blue whale, sleeps — yet scientists can’t explain why any organism would leave itself vulnerable to predators, and unable to eat or mate, for a large portion of the day. Now, researchers have demonstrated for the first time that even an organism without a brain — a kind of jellyfish — shows sleep-like behaviour, suggesting that the origins of sleep are more primitive than thought. Researchers observed that the rate at which Cassiopea jellyfish pulsed their bell decreased by one-third at night, and the animals were much slower to respond to external stimuli such as food or movement during that time. When deprived of their night-time rest, the jellies were less active the next day. “Everyone we talk to has an opinion about whether or not jellyfish sleep. It really forces them to grapple with the question of what sleep is,” says Ravi Nath, the paper’s first author and a molecular geneticist at the California Institute of Technology (Caltech) in Pasadena. The study was published on 21 September in Current Biology1. “This work provides compelling evidence for how early in evolution a sleep-like state evolved,” says Dion Dickman, a neuroscientist at the University of Southern California in Los Angeles. Nath is studying sleep in the worm Caenorhabditis elegans, but whenever he presented his work at research conferences, other scientists scoffed at the idea that such a simple animal could sleep. The question got Nath thinking: how minimal can an animal’s nervous system get before the creature lacks the ability to sleep? Nath’s obsession soon infected his friends and fellow Caltech PhD students Michael Abrams and Claire Bedbrook. Abrams works on jellyfish, and he suggested that one of these creatures would be a suitable model organism, because jellies have neurons but no central nervous system. Instead, their neurons connect in a decentralized neural net. © 2017 Macmillan Publishers Limited

Keyword: Sleep; Evolution
Link ID: 24096 - Posted: 09.22.2017

James Gorman Imagine a species that lived in a world of smells and didn’t pay a lot of attention to what things look like. What would members of that species use for a mirror? Would they even want a mirror? Yes, of course, we are talking about dogs, who usually don’t seem to understand the mirrors humans use. Sometimes they ignore them. Often they bark as if the dog in the mirror were a stranger. Scientists use mirrors to find out if animals recognize themselves, to see if they have some sense of self. Chimpanzees do very well on what is called the mirror test. A chimp will notice a mark on his face and perhaps even use the mirror to aid in removing it. He might use the mirror to examine parts of his body he can’t normally see, like the inside of his mouth. Researchers have reported that dolphins, one elephant and a magpie have also passed this test. Dogs have not, and that has raised questions about whether dogs might recognize themselves if another sense were tested. Alexandra Horowitz, a psychologist at Barnard College who studies the behavior of dogs and has written several books about them, decided to give dogs a chance at showing self-recognition on their own, smelly terms. In a recent study, she concludes that they do recognize the smell of their own urine. While some researchers find the study intriguing, the scientist who first developed that mirror mark test doesn’t think the evidence supports her conclusion. Still, even the idea of a smell mirror is mind (nose?) boggling. “I had always flirted with the idea in my head that there should be an olfactory mirror,” Dr. Horowitz said, acknowledging that “it could be horrifying for humans.” © 2017 The New York Times Company

Keyword: Chemical Senses (Smell & Taste); Consciousness
Link ID: 24095 - Posted: 09.22.2017

Katherine Ellen Foley, Youyou Zhou, Christopher Groskopf One way to understand long-term trends in medical and health research is to analyze the language used in massive bodies of literature produced in the different fields. To better understand the shifting focus of sex research since the field was established, we downloaded (with permission) 4,545 articles published in the Journal of Sex Research and the Archives of Sexual Behavior from 1970 to 2017, and tracked just over 1,000 of the most-used words in these studies. You can use the tool below to explore all of these words, and see how their frequency in the literature has changed over time. Beneath it, we’ve pulled out some of the most interesting trends we noticed and investigated possible explanations for why they’ve occurred. Humans have been having sex since as long as we’ve been on the planet, but it wasn’t until recently that we really started studying it. Sexology became a serious field just after World War II, starting with the work of Alfred Kinsey, a biologist at Indiana University, and later founder of the school’s Kinsey Institute, which today studies love and sexuality. Kinsey published his first book, Sexual Behavior in the Human Male, in 1948, followed by Sexual Behavior in the Human Female in 1953. In the 1960s, the field was further advanced by the work of lab mates (and lovers) William Masters and Victoria Johnson, who published the seminal Human Sexual Response in 1966.

Keyword: Sexual Behavior
Link ID: 24094 - Posted: 09.22.2017

By Gary Stix Donald Hebb was a famed Canadian scientist who produced key findings that ranged across the field of psychology, providing insights into perception, intelligence and emotion. He is perhaps best known, though, for his theory of learning and memory, which appears as an entry in most basic texts on neuroscience. But now an alternative theory—along with accompanying experimental evidence—fundamentally challenges some central tenets of Hebb’s thinking. It provides a detailed account of how cells and the electrical and molecular signals that activate them are involved in forming memories of a series of related events. Put forward in 1949, Hebb’s theory holds that when electrical activity in one neuron—perhaps triggered by observing one’s surroundings—repeatedly induces a neighboring “target cell” to fire electrical impulses, a process of conditioning occurs and strengthens the connection between the two neurons. This is a bit like doing arm curls with a weight; after repeated lifts the arm muscle grows stronger and the barbell gets easier to hoist. At the cellular level, repeated stimulation of one neuron by another enables the target cell to respond more readily the next time it is activated. In basic textbooks, this boils down to a simple adage to describe the physiology of learning and memory: “Cells that fire together, wire together.” Every theory requires experimental evidence, and scientists have toiled for years to validate Hebb’s idea in the laboratory. Many research findings have showed that when a neuron repeatedly fires off an electrical impulse (called an “action potential”) at virtually the same time as an adjacent neuron, their connection does indeed grow more efficient. The target cell fires more easily, and the signal transmitted is stronger. This process—known as long-term potentiation (LTP)—apparently induces physiological change or “plasticity” in target cells. LTP is routinely cited as a possible explanation for how the brain learns and forms memories at the cellular level. © 2017 Scientific American,

Keyword: Learning & Memory
Link ID: 24093 - Posted: 09.21.2017

By Ariana Eunjung Cha Over the past two decades, U.S. parents and teachers have reported epidemic levels of children with trouble focusing, impulsive behavior and so much energy that they are bouncing off walls. Educators, policymakers and scientists have referred to attention-deficit/hyperactivity disorder, or ADHD, as a national crisis and have spent billions of dollars looking into its cause. They've looked at genetics, brain development, exposure to lead, the push for early academics, and many other factors. But what if the answer to at least some cases of ADHD is more obvious? What if, as a growing number of researchers are proposing, many kids today simply aren't getting the sleep they need, leading to challenging behaviors that mimic ADHD? That provocative and controversial theory has been gaining momentum in recent years, with several studies suggesting strong links between ADHD and the length, timing and quality of sleep. In an era in which even toddlers know the words Netflix and Hulu, when demands for perfectionism extend to squirmy preschoolers and many elementary-age students juggle multiple extracurricular activities each day, one question is whether some kids are so stimulated or stressed that they are unable to sleep as much or as well as they should. Growing evidence suggests that a segment of children with ADHD are misdiagnosed and actually suffer from insufficient sleep, insomnia, obstructed breathing or another known sleep disorder. But the most paradigm-challenging idea may be that ADHD may itself be a sleep disorder. If correct, this idea could fundamentally change the way ADHD is studied and treated. © 1996-2017 The Washington Post

Keyword: ADHD; Sleep
Link ID: 24092 - Posted: 09.21.2017

By Alla Katsnelson, Men and women both transmit an increasing number of new mutations to their children as they age, according to a study published today in Nature1. The finding is based on an analysis of whole genomes from nearly 5,000 people. The increase in these ‘de novo’ mutations may explain why older parents are more likely to have a child with a condition such as autism. Men accumulate de novo mutations four times faster than women, the researchers found. However, in about 10 percent of the genome, mutations accumulate twice as quickly as elsewhere, and appear at an equal rate in both women and men. “The majority of the contribution still comes from the father, particularly when the father is in an older age range,” says lead investigator Kári Stefánsson, chief executive of deCODE Genetics. “But the mutation rate is not equal across the genome, so we have to make sure we do not generalize too much.” The new study builds on earlier work by deCODE Genetics, a company based in Reykjavik, Iceland. In 2012, the researchers reported that the rate at which people acquire mutations and pass them down to their children increases sharply with age in men but stays level in women. Those findings were based on whole-genome sequences from just 78 individuals and their parents. The findings provide one possible explanation for the increased risk of autism among children born to older parents. © 2017 Scientific American

Keyword: Sexual Behavior; Genes & Behavior
Link ID: 24091 - Posted: 09.21.2017

While immune cells called neutrophils are known to act as infantry in the body’s war on germs, a National Institutes of Health-funded study suggests they can act as medics as well. By studying rodents, researchers showed that instead of attacking germs, some neutrophils may help heal the brain after an intracerebral hemorrhage, a form of stroke caused by ruptured blood vessels. The study suggests that two neutrophil-related proteins may play critical roles in protecting the brain from stroke-induced damage and could be used as treatments for intracerebral hemorrhage. “Intracerebral hemorrhage is a damaging and often fatal form of stroke for which there are no effective medicines,” said Jaroslaw Aronowski, M.D., Ph.D., professor, department of neurology, at the University of Texas Health Science Center at Houston, and senior author of the study published in Nature Communications. “Our results are a hopeful first step towards developing a treatment for this devastating form of stroke.” Accounting for 10 to 15 percent of all strokes, intracerebral hemorrhages happen when blood vessels rupture and leak blood into the brain, often leading to death or long-term disability. Chronic high blood pressure is the leading risk factor for these types of strokes. The initial phase of damage appears to be caused by the pressure of blood leaking into the brain. Over time, further damage may be caused by the accumulation of toxic levels of blood products, infiltrating immune cells, and swelling. Decades of research suggest that neutrophils are some of the earliest immune cells to respond to a hemorrhage, and that they may both harm and heal the brain.

Keyword: Stroke; Neuroimmunology
Link ID: 24090 - Posted: 09.21.2017

Amber Dance Ninad Kothari’s workplace looks like something out of a sci-fi film. The graduate student at Johns Hopkins University works in a darkened, red-lit room, where he trains bats to fly through obstacle courses. Shielding within the walls keeps radio and other human-made signals from interfering with transmissions from the tiny electrical signals he’s recording from the bats’ brains as the animals bob and weave. Layers of foam further insulate the cavelike lab against sound waves. An array of cameras and microphones complete the futuristic scene. The high-tech setup has its homemade touches, too: In one obstacle course, bats dodge dangling Quaker oatmeal cylinders. Kothari is part of a small cadre of neuroscientists who are getting the best sense yet of how bat brains work at a cellular level, thanks to modern technologies. Eavesdropping tools, which rely on tiny probes that track the activities of individual nerve cells, or neurons, are now miniaturized enough to outfit bats with head-mounted, wireless sensors. As the animals fly freely around the lab, the researchers can listen in on neurons. By allowing the bats to behave naturally, unencumbered by bulky equipment, scientists will discover exciting new facets of how bat brains work, says neuroscientist Nachum Ulanovsky of the Weizmann Institute of Science in Rehovot, Israel, who invented the new wireless sensors with colleagues. He and others, studying several different species of bats, are investigating how the flying mammals perceive their environment and navigate through it. |© Society for Science & the Public 2000 - 2017

Keyword: Hearing
Link ID: 24089 - Posted: 09.21.2017

Patrick Barkham Humans trying to chat each other up in a noisy nightclub may find verbal communication futile. But it appears even more pointless for pumpkin toadlets after scientists discovered that females have lost the ability to hear the sound of male mating calls. An international team from Brazil, Denmark and the UK has discovered that the males of two species of tiny orange frogs continue to make high-pitched calls despite neither females nor males being able to hear them. It is believed to be the first case in the animal kingdom of a communication signal enduring even after its target audience has lost the ability to detect it. Field studies began in Brazil’s Atlantic forest by playing frog calls to determine how these species, which possess a middle ear, could hear their own calls. Lead researcher Dr Sandra Goutte at the Universidade Estadual de Campinas, São Paulo, was surprised to find the frogs refused to respond to her playback communication, didn’t change their calling behaviour and didn’t even orient themselves towards the sounds. “I thought I would find the sound transmission pathway from the outside to the middle ear,” she said. “We didn’t think it would be possible that they would not be able to hear their own calls.” © 2017 Guardian News and Media Limited

Keyword: Hearing; Sexual Behavior
Link ID: 24088 - Posted: 09.21.2017

by Emilie Reas Paranoia. Munchies. Giggles. Sleepiness. Memory loss. Although the effects of cannabinoids–the active components of marijuana–are familiar to many, their neurobiological substrates are poorly characterized. Perhaps the effect of greatest interest to both neuroscientists and to cannabis users hoping to preserve their cognitive function, is short-term memory impairment that often accompanies marijuana use. Our partial understanding of its physiological and behavioral effects is not for want of studies into its neural effects. Ample research has shown a range of changes to neurotransmission, receptors, ion channels and mitochondria following cannabinoid exposure. However, knowledge of its cellular and molecular properties alone cannot offer a complete picture of its system-wide effects leading to cognitive and behavioral changes. A recent study published in PLOS Computational Biology took a novel approach to address this issue, combining computational modeling with electrophysiological brain recordings from rats performing a memory task, to unravel the dynamics of neural circuits under the influence of cannabinoids. To assess memory changes induced by cannabinoids, the scientists injected tetrahydrocannabinol (THC), the main psychoactive compound in marijuana, into rats before they performed a “delayed-nonmatch-to-sample” working memory task. In this task, rats are cued with one of two levers, and after a delay, are required to select the opposite lever. Compared to sober sessions, performance under THC was impaired by 12%, confirming the all-too-familiar memory impairment associated with cannabis use. THC alters hippocampal activity

Keyword: Learning & Memory; Drug Abuse
Link ID: 24087 - Posted: 09.21.2017

Amy Maxmen Male ducks respond to sexual competition by growing either an extra-long penis or a nub of flesh, a new study finds. The unusual phenomena occurred in two species studied: the lesser scaup (Aythya affinis) and the ruddy duck (Oxyura jamaicensis). It suggests that penis size — in line with many traits and behaviours meant to impress or allow impregnation of the opposite sex — involves a trade-off between the potential to reproduce and to survive. Patricia Brennan, an evolutionary biologist at Mount Holyoke College in South Hadley, Massachusetts, compared the penises of ducks kept in male–female pairs to those housed with multiple males per female. The findings are published in a study on 20 September in The Auk: Ornithological Advances1. “If they were alone with a female, the males just grew a normal-sized penis, but if there were other males around, they had the ability to change dramatically,” Brennan says. “So evolution must be acting on the ability to be plastic — the ability to invest only in what is needed in your current circumstance.” Because evolutionary success relies on reproduction, genitals are adapted to meet the varied circumstances that every animal faces. Some male ducks, for example, have penises in the shape of corkscrews to navigate the labyrinth-like vaginas of their female counterparts. An earlier study by Brennan found that females’ anatomy evolved to prevent access to undesirable males who force copulation2. To mate successfully with their chosen partners, Brennan says, female ducks assume a posture that allows males to enter them fully and deposit sperm near eggs. © 2017 Macmillan Publishers Limited,

Keyword: Sexual Behavior; Evolution
Link ID: 24086 - Posted: 09.21.2017

Cordelia Fine argues no; Joe Herbert says yes. Cordelia Fine: A common assumption, which I refer to as the ‘Testosterone Rex’ view, is that testosterone is a proximal tool of distal evolutionary processes, acting via the brain (prenatally, then from pubescence) to shape sex differences in behaviour that would have been differentially reproductively advantageous for men versus women in our ancestral past. Joe, as you put it in your book Testosterone: Sex, power and the will to win, ‘for [male] reproduction to be successful, testosterone has to act on many parts of the male to make him fit for the competitive world of male sexuality’. So, for example, males’ greater testosterone exposure predisposes them to be more risk-taking and competitive than females – an idea sometimes called on to help explain gender gaps in risky and competitive occupations, a category which happens to include most high-status and well-remunerated roles. So what exactly does testosterone do? Testosterone acts directly on the brain, but the circulating level of testosterone in the blood is just one part of a highly complex, multi-faceted system. What’s more, different species appear to tweak those system dials in different ways, enabling cross-species differences in relations between hormones and behaviour. What do we need to try to explain when it comes to humans? One important feature of sex differences in behaviour is that these are much smaller than sex differences in testosterone exposure (a lot of overlap between female and male populations, and very little, respectively). This casts serious doubt on the assumption that more testosterone means more masculinity, and that men must inevitably be more masculine because they have higher absolute levels of testosterone on average. © Copyright 2000-2017 The British Psychological Society

Keyword: Sexual Behavior
Link ID: 24085 - Posted: 09.20.2017