Chapter 17. Learning and Memory
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By Elizabeth Pennisi "What's for dinner?" The words roll off the tongue without even thinking about it—for adults, at least. But how do humans learn to speak as children? Now, a new study in mice shows how a gene, called FOXP2, implicated in a language disorder may have changed between humans and chimps to make learning to speak possible—or at least a little easier. As a uniquely human trait, language has long baffled evolutionary biologists. Not until FOXP2 was linked to a genetic disorder that caused problems in forming words could they even begin to study language’s roots in our genes. Soon after that discovery, a team at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, discovered that just two bases, the letters that make up DNA, distinguished the human and chimp versions of FOXP2. To try to determine how those changes influenced the gene's function, that group put the human version of the gene in mice. In 2009, they observed that these "humanized" mice produced more frequent and complex alarm calls, suggesting the human mutations may have been involved in the evolution of more complex speech. Another study showed that humanized mice have different activity in the part of the brain called the striatum, which is involved in learning, among other tasks. But the details of how the human FOXP2 mutations might affect real-world learning remained murky. To solve the mystery, the Max Planck researchers sent graduate student Christiane Schreiweis to work with Ann Graybiel, a neuroscientist at the Massachusetts Institute of Technology in Cambridge. She's an expert in testing mouse smarts by seeing how quickly they can learn to find rewards in mazes. © 2014 American Association for the Advancement of Science
by Michael Slezak It's one of the biggest mysteries of Alzheimer's. The disease is associated with the formation of protein plaques in the brain, but why is it that some people with plaques seem not to have the disease? Research suggests that some people's brains are able to reorganise during the early stages of Alzheimer's, delaying the appearance of initial symptoms. The plaques in question are small mounds of a protein called beta-amyloid, and are found in the brains of people with Alzheimer's disease. Whether these plaques are a cause of the disease has been hotly debated. One reason for doubt is the appearance of plaques in many older people who have no symptoms Movie Cameraof dementia at all. Using fMRI to measure changes in blood flow around the brain, William Jagust from the University of California in Berkley and colleagues compared brain function in three groups of people without symptoms of dementia: 22 young people, 16 older people with beta-amyloid plaques and 33 older people without the plaques. He asked each of them to memorise a photographed scene while inside the machine. Jagust found that older people with plaques had increased blood flow – which means stronger activation of that brain area – in the regions of the brain that are usually activated during memory formation, compared with the older people who did not have plaques. The team then analysed whether this extra brain activation might be helping to compensate for the plaques. © Copyright Reed Business Information Ltd.
by Simon Makin Talking in your sleep might be annoying, but listening may yet prove useful. Researchers have shown that sleeping brains not only recognise words, but can also categorise them and respond in a previously defined way. This could one day help us learn more efficiently. Sleep appears to render most of us dead to the world, our senses temporarily suspended, but sleep researchers know this is a misleading impression. For instance, a study published in 2012 showed that sleeping people can learn to associate specific sounds and smells. Other work has demonstrated that presenting sounds or smells during sleep boosts performance on memory tasks – providing the sensory cues were also present during the initial learning. Now it seems the capabilities of sleeping brains stretch even further. A team led by Sid Kouider from the Ecole Normale Supérieur in Paris trained 18 volunteers to classify spoken words as either animal or object by pressing buttons with their right or left hand. Brain activity was recorded using EEG, allowing the researchers to measure the telltale spikes in activity that indicate the volunteers were preparing to move one of their hands. Since each hand is controlled by the motor cortex on the opposite side of the brain, these brainwaves can be matched to the intended hand just by looking at which side of the motor cortex is active. © Copyright Reed Business Information Ltd.
By Helen Briggs Health editor, BBC News website There may be a link between a rare blood type and memory loss in later life, American research suggests. People with AB blood, found in 4% of the population, appear more likely to develop thinking and memory problems than those with other blood groups. The study, published in Neurology, builds on previous research showing blood type may influence heart risk. A charity said the best way to keep the brain healthy was a balanced diet, regular exercise and not smoking. A US team led by Dr Mary Cushman, of the University of Vermont College of Medicine, Burlington, analysed data from about 30,000 US citizens aged 45 and above. It identified 495 participants who had developed thinking and memory problems, or cognitive impairment, during the three-year study. They were compared to 587 people with no cognitive problems. People with AB blood type made up 6% of the group who developed cognitive impairment, which is higher than the 4% found in the general population. They were 82% more likely to have difficulties with day-to-day memory, language and attention, which can signal the onset of dementia. However, the study did not look at the risk of dementia. The study supported the idea that having a certain blood group, such as O, may give a lower risk for cardiovascular disease, which in turn protected the brain, the researchers said. "Our study looks at blood type and risk of cognitive impairment, but several studies have shown that factors such as high blood pressure, high cholesterol and diabetes increase the risk of cognitive impairment and dementia," said Dr Cushman. BBC © 2014
By BENEDICT CAREY Imagine that on Day 1 of a difficult course, before you studied a single thing, you got hold of the final exam. The motherlode itself, full text, right there in your email inbox — attached mistakenly by the teacher, perhaps, or poached by a campus hacker. No answer key, no notes or guidelines. Just the questions. Would that help you study more effectively? Of course it would. You would read the questions carefully. You would know exactly what to focus on in your notes. Your ears would perk up anytime the teacher mentioned something relevant to a specific question. You would search the textbook for its discussion of each question. If you were thorough, you would have memorized the answer to every item before the course ended. On the day of that final, you would be the first to finish, sauntering out with an A+ in your pocket. And you would be cheating. But what if, instead, you took a test on Day 1 that was just as comprehensive as the final but not a replica? You would bomb the thing, for sure. You might not understand a single question. And yet as disorienting as that experience might feel, it would alter how you subsequently tuned into the course itself — and could sharply improve your overall performance. This is the idea behind pretesting, one of the most exciting developments in learning-science. Across a variety of experiments, psychologists have found that, in some circumstances, wrong answers on a pretest aren’t merely useless guesses. Rather, the attempts themselves change how we think about and store the information contained in the questions. On some kinds of tests, particularly multiple-choice, we benefit from answering incorrectly by, in effect, priming our brain for what’s coming later. That is: The (bombed) pretest drives home the information in a way that studying as usual does not. We fail, but we fail forward. © 2014 The New York Times Company
Keyword: Learning & Memory
Link ID: 20043 - Posted: 09.08.2014
by Sandrine Ceurstemont Screening an instructional monkey movie in a forest reveals that marmosets do not only learn from family members: they also copy on-screen strangers. It is the first time such a video has been used for investigations in the wild. Tina Gunhold at the University of Vienna, Austria, and her colleagues filmed a common marmoset retrieving a treat from a plastic device. They then took the device to the Atlantic Forest near Aldeia in Pernambuco, Brazil, and showed the movie to wild marmosets there. Although monkeys are known to learn from others in their social group, especially when they are youngMovie Camera, little is known about their ability to learn from monkeys that do not belong to the same group. Marmosets are territorial, so the presence of an outsider – even a virtual one on a screen – could provoke an attack. "We didn't know if wild marmosets would be frightened of the video box but actually they were all attracted to it," says Gunhold. Compared to monkeys shown a static image of the stranger, video-watching marmosets were more likely to manipulate the device, typically copying the technique shown (see video). Young monkeys spent more time near the video box than older family members, suggesting that they found the movie more engaging – although as soon as one monkey mastered the task, it was impossible to tell whether the others were learning from the video or from their relative. "We think it's a combination of both," says Gunhold. © Copyright Reed Business Information Ltd.
By Virginia Morell Figaro, a Goffin’s cockatoo (Cacatua goffini) housed at a research lab in Austria, stunned scientists a few years ago when he began spontaneously making stick tools from the wooden beams of his aviary. The Indonesian parrots are not known to use tools in the wild, yet Figaro confidently employed his sticks to rake in nuts outside his wire enclosure. Wondering if Figaro’s fellow cockatoos could learn by watching his methods, scientists set up experiments for a dozen of them. One group watched as Figaro used a stick to reach a nut placed inside an acrylic box with a wire-mesh front panel; others saw “ghost demonstrators”—magnets that were hidden beneath a table and that the researchers controlled—displace the treats. Each bird was then placed in front of the box, with a stick just like Figaro’s lying nearby. The group of three males and three females that had watched Figaro also picked up the sticks, and made some efforts reminiscent of his actions. But only those three males, such as the one in the photo above, became proficient with the tool and successfully retrieved the nuts, the scientists report online today in the Proceedings of the Royal Society B. None of the females did so; nor did any of the birds, male or female, in the ghost demonstrator group. Because the latter group failed entirely, the study shows that the birds need living teachers, the scientists say. Intriguingly, the clever observers developed a better technique than Figaro’s for getting the treat. Thus, the cockatoos weren’t copying his exact actions, but emulating them—a distinction that implies some degree of creativity. Two of the successful cockatoos were later given a chance to make a tool of their own. One did so immediately (as in the video above), and the other succeeded after watching Figaro. It may be that by learning to use a tool, the birds are stimulated to make tools of their own, the scientists say. © 2014 American Association for the Advancement of Science.
Keyword: Learning & Memory
Link ID: 20027 - Posted: 09.03.2014
by Chris Higgins Neuroscientists have pinpointed where imagination hides in the brain and found it to be functionally distinct from related processes such as memory. The team from Brigham Young University (BYU), Utah-- including research proposer, undergraduate student Stefania Ashby -- used functional Magnetic Resonance Imaging (fMRI) to observe brain activity when subjects were remembering specific experiences and putting themselves in novel ones. "I was thinking a lot about planning for my own future and imagining myself in the future, and I started wondering how memory and imagination work together," Ashby said. "I wondered if they were separate or if imagination is just taking past memories and combining them in different ways to form something I've never experienced before." The two processes of remembering and imagining have been previously proposed to be the same cognitive task, and so thought to be carried out by the same areas of the brain. However, the experiments derived by Ashby and her mentor (and coauthor) BYU professor Brock Kirwan have refuted these ideas. The studies -- published in the journal Cognitive Neuroscience -- required participants to submit 60 photographs of previous life events and use them to create prompts for the "remember" sections. They then carried out a questionnaire before putting the subject into the MRI scanner to determine what scenarios were the most novel to them and force them into imagination. Then, under fMRI testing, the subjects were prompted with various scenarios and the areas of their brain that became active during each scenario was correlated with each scene's familiarity -- pure memory, or imagination. © Condé Nast UK 2014
By JOHN ROGERS LOS ANGELES (AP) — The founder of a Los Angeles-based nonprofit that provides free music lessons to low-income students from gang-ridden neighborhoods began to notice several years ago a hopeful sign: Kids were graduating high school and heading off to UCLA, Tulane and other big universities. That’s when Margaret Martin asked how the children in the Harmony Project were beating the odds. Researchers at Northwestern University in Illinois believe that the students’ music training played a role in their educational achievement, helping as Martin noticed 90 percent of them graduate from high school while 50 percent or more didn’t from those same neighborhoods. A two-year study of 44 children in the program shows that the training changes the brain in ways that make it easier for youngsters to process sounds, according to results reported in Tuesday’s edition of The Journal of Neuroscience. That increased ability, the researchers say, is linked directly to improved skills in such subjects as reading and speech. But, there is one catch: People have to actually play an instrument to get smarter. They can’t just crank up the tunes on their iPod. Nina Kraus, the study’s lead researcher and director of Northwestern’s auditory neuroscience laboratory, compared the difference to that of building up one’s body through exercise. ‘‘I like to say to people: You’re not going to get physically fit just watching sports,’’ she said.
Memory can be boosted by using a magnetic field to stimulate part of the brain, a study has shown. The effect lasts at least 24 hours after the stimulation is given, improving the ability of volunteers to remember words linked to photos of faces. Scientists believe the discovery could lead to new treatments for loss of memory function caused by ageing, strokes, head injuries and early Alzheimer's disease. Dr Joel Voss, from Northwestern University in Chicago, said: "We show for the first time that you can specifically change memory functions of the brain in adults without surgery or drugs, which have not proven effective. "This non-invasive stimulation improves the ability to learn new things. It has tremendous potential for treating memory disorders." The scientists focused on associative memory, the ability to learn and remember relationships between unrelated items. An example of associative memory would be linking someone to a particular restaurant where you both once dined. It involves a network of different brain regions working in concert with a key memory structure called the hippocampus, which has been compared to an "orchestra conductor" directing brain activity. Stimulating the hippocampus caused the "musicians" – the brain regions – to "play" more in time, thereby tightening up their performance. A total of 16 volunteers aged 21-40 took part in the study, agreeing to undergo 20 minutes of transcranial magnetic stimulation (TMS) every day for five days. © 2014 Guardian News and Media Limited
Keyword: Learning & Memory
Link ID: 20015 - Posted: 08.30.2014
by Michael Slezak It's odourless, colourless, tasteless and mostly non-reactive – but it may help you forget. Xenon gas has been shown to erase fearful memories in mice, raising the possibility that it could be used to treat post-traumatic stress disorder (PTSD) if the results are replicated in a human trial next year. The method exploits a neurological process known as "reconsolidation". When memories are recalled, they seem to get re-encoded, almost like a new memory. When this process is taking place, the memories become malleable and can be subtly altered. This new research suggests that at least in mice, the reconsolidation process might be partially blocked by xenon, essentially erasing fearful memories. Among other things, xenon is used as an anaesthetic. Frozen in fear Edward Meloni and his colleagues at Harvard Medical School in Boston trained mice to be afraid of a sound by placing them in a cage and giving them an electric shock after the sound was played. Thereafter, if the mice heard the noise, they would become frightened and freeze. Later, the team played the sound and then gave the mice either a low dose of xenon gas for an hour or just exposed them to normal air. Mice that were exposed to xenon froze for less time in response to the sound than the other mice. © Copyright Reed Business Information Ltd.
Keyword: Learning & Memory
Link ID: 20014 - Posted: 08.30.2014
By PAM BELLUCK Memories and the feelings associated with them are not set in stone. You may have happy memories about your family’s annual ski vacation, but if you see a tragic accident on the slopes, those feelings may change. You might even be afraid to ski that mountain again. Now, using a technique in which light is used to switch neurons on and off, neuroscientists at the Massachusetts Institute of Technology appear to have unlocked some secrets about how the brain attaches emotions to memories and how those emotions can be adjusted. Their research, published Wednesday in the journal Nature, was conducted on mice, not humans, so the findings cannot immediately be translated to the treatment of patients. But experts said the experiments may eventually lead to more effective therapies for people with psychological problems such as depression, anxiety or post-traumatic stress disorder. “Imagine you can go in and find a particular traumatic memory and turn it off or change it somehow,” said David Moorman, an assistant professor of psychological and brain sciences at the University of Massachusetts Amherst, who was not involved in the research. “That’s still science fiction, but with this we’re getting a lot closer to it.” The M.I.T. scientists labeled neurons in the brains of mice with a light-sensitive protein and used pulses of light to switch the cells on and off, a technique called optogenetics. Then they identified patterns of neurons activated when mice created a negative memory or a positive one. A negative memory formed when mice received a mild electric shock to their feet; a positive one was formed when the mice, all male, were allowed to spend time with female mice. © 2014 The New York Times Company
by Penny Sarchet Memory is a fickle beast. A bad experience can turn a once-loved coffee shop or holiday destination into a place to be avoided. Now experiments in mice have shown how such associations can be reversed. When forming a memory of a place, the details of the location and the associated emotions are encoded in different regions of the brain. Memories of the place are formed in the hippocampus, whereas positive or negative associations are encoded in the amygdala. In experiments with mice in 2012, a group led by Susumo Tonegawa of the Massachusetts Institute of Technology managed to trigger the fear part of a memory associated with a location when the animals were in a different location. They used a technique known as optogenetics, which involves genetically engineering mice so that their brains produce a light-sensitive protein in response to a certain cue. In this case, the cue was the formation of the location memory. This meant the team could make the mouse recall the location just by flashing pulses of light down an optical fibre embedded in the skull. The mice were given electric shocks while their memories of the place were was being formed, so that the animals learned to associate that location with pain. Once trained, the mice were put in a new place and a pulse of light was flashed into their brains. This activated the neurons associated with the original location memory and the mice froze, terrified of a shock, demonstrating that the emotion associated with the original location could be induced by reactivating the memory of the place. © Copyright Reed Business Information Ltd.
Learning is easier when it only requires nerve cells to rearrange existing patterns of activity than when the nerve cells have to generate new patterns, a study of monkeys has found. The scientists explored the brain’s capacity to learn through recordings of electrical activity of brain cell networks. The study was partly funded by the National Institutes of Health. “We looked into the brain and may have seen why it’s so hard to think outside the box,” said Aaron Batista, Ph.D., an assistant professor at the University of Pittsburgh and a senior author of the study published in Nature, with Byron Yu, Ph.D., assistant professor at Carnegie Mellon University, Pittsburgh. The human brain contains nearly 86 billion neurons, which communicate through intricate networks of connections. Understanding how they work together during learning can be challenging. Dr. Batista and his colleagues combined two innovative technologies, brain-computer interfaces and machine learning, to study patterns of activity among neurons in monkey brains as the animals learned to use their thoughts to move a computer cursor. “This is a fundamental advance in understanding the neurobiological patterns that underlie the learning process,” said Theresa Cruz, Ph.D., a program official at the National Center for Medical Rehabilitations Research at NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). “The findings may eventually lead to new treatments for stroke as well as other neurological disorders.”
|By Michael Leon I had been working quite happily on the basic biology of the brain when a good friend of mine called for advice about his daughter, who had just been diagnosed with autism. I could hear the anguish and fear in his voice when he asked me whether there was anything that could be done to make her better. I told him about the standard-care therapies, including Intensive Behavioral Intervention, Early Intensive Behavioral Intervention, Applied Behavior Analysis, and the Early Start Denver Model (ESDM). These therapies also are expensive, time-consuming and have variable outcomes, with the best outcomes seen for ESDM. There are, however, few ESDM therapists, and the cost of such intensive therapy can be quite high. Moreover, my friend’s daughter was already past the age of the oldest children in the study that demonstrated the efficacy of ESDM. My feeling was that there was a good chance that there was an effective therapy for her using a simple, inexpensive at-home approach involving daily exposure to a wide variety of sensory stimulation. This is a partial list of the disorders whose symptoms can be greatly reduced, or even completely reversed, with what is known as “environmental enrichment”: Autism Stroke Seizures Brain damage Neuronal death during aging ADHD Prenatal alcohol syndrome Lead exposure Multiple sclerosis Addiction Schizophrenia Memory loss Huntington’s disease Parkinson’s disease Alzheimer’s disease Down syndrome Depression But why haven’t you heard about this? The reason is that all of these disorders that have been successfully treated only in animal models of these neurological problems. However, the effects seen in lab animals can be dramatic. © 2014 Scientific American,
|By Roni Jacobson Children are notoriously unreliable witnesses. Conventional wisdom holds that they frequently “remember” things that never happened. Yet a large body of research indicates that adults actually generate more false memories than children. Now a new study finds that children are just as susceptible to false memories as adults, if not more so. Scientists may simply have been using the wrong test. Traditionally, researchers have explored false memories by presenting test subjects with a list of associated words (for instance, “weep,” “sorrow” and “wet”) thematically related to a word not on the list (in this case, “cry”) and then asking them what words they remember. Adults typically mention the missing related word more often than children do—possibly because their life experiences enable them to draw associations between concepts more readily, says Henry Otgaar, a forensic psychologist at Maastricht University in the Netherlands and co-author of the new paper, published in May in the Journal of Experimental Child Psychology. Instead of using word lists to investigate false memories, Otgaar and his colleagues showed participants pictures of scenes, including a classroom, a funeral and a beach. After a short break, they asked those participants whether they remembered seeing certain objects in each picture. Across three experiments, seven- and eight-year-old children consistently reported seeing more objects that were not in the pictures than adults did. © 2014 Scientific American
|By Jason G. Goldman When you do not know the answer to a question, say, a crossword puzzle hint, you realize your shortcomings and devise a strategy for finding the missing information. The ability to identify the state of your knowledge—thinking about thinking—is known as metacognition. It is hard to tell whether other animals are also capable of metacognition because we cannot ask them; studies of primates and birds have not yet been able to rule out simpler explanations for this complex process. Scientists know, however, that some animals, such as western scrub jays, can plan for the future. Western scrub jays, corvids native to western North America, are a favorite of cognitive scientists because they are not “stuck in time”—that is, they are able to remember past events and are known to cache their food in anticipation of hunger, according to psychologist Arii Watanabe of the University of Cambridge. But the question remained: Are they aware that they are planning? Watanabe devised a way to test them. He let five birds watch two researchers hide food, in this case a wax worm. The first researcher could hide the food in any of four cups lined up in front of him. The second had three covered cups, so he could place the food only in the open one. The trick was that the researchers hid their food at the same time, forcing the birds to choose which one to watch. If the jays were capable of metacognition, Watanabe surmised, the birds should realize that they could easily find the second researcher's food. The wax worm had to be in the singular open cup. They should instead prefer keeping their eyes on the setup with four open cups because witnessing where that food went would prove more useful in the future. And that is exactly what happened: the jays spent more time watching the first researcher. The results appeared in the July issue of the journal © 2014 Scientific American,
by Sarah Zielinski PRINCETON, N.J. — Learning can be a quick shortcut for figuring out how to do something on your own. The ability to learn from watching another individual — called social learning — is something that hasn’t been documented in many species outside of primates and birds. But now a lizard can be added to the list of critters that can learn from one another. Young eastern water skinks were able to learn by watching older lizards, Martin Whiting of Macquarie University in Sydney reported August 10 at the Animal Behavior Society meeting at Princeton University. The eastern water skink, which reaches a length of about 30 centimeters, can be found near streams and waterways in eastern Australia. The lizards live up to eight years, and while they don’t live in groups, they often see each other in the wild. That could provide an opportunity for learning from each other. Whiting and his colleagues worked with 18 mature (older than 5 years) and 18 young (1.5 to 2 years) male skinks in the lab. The lizards were placed in bins with a barrier in the middle that was either opaque or transparent. In the first of two experiments, the skinks were given a yellow-lidded container with a mealworm inside. They had to learn to open the lid to get the food. In that task, skinks that could see a demonstrator through a transparent barrier were no better at opening the lid than those who had to figure it out on their own. After watching a demonstrator lizard (top row), the skink in the other half of the tub was supposed to have learned that a mealworm was beneath the blue lid. The skink in the middle arena, however, failed the task when he opened the white lid first.D.W.A. Noble et al/Biology Letters 2014 © Society for Science & the Public 2000 - 2013.
by Bethany Brookshire Every day sees a new research article on addiction, be it cocaine, heroin, food or porn. Each one takes a specific angle on how addiction works in the brain. Perhaps it’s a disorder of reward, with drugs hijacking a natural system that is meant to respond to food, sex and friendship. Possibly addiction is a disorder of learning, where our brains learn bad habits and responses. Maybe we should think of addiction as a combination of an environmental stimulus and vulnerable genes. Or perhaps it’s an inappropriate response to stress, where bad days trigger a relapse to the cigarette, syringe or bottle. None of these views are wrong. But none of them are complete, either. Addiction is a disorder of reward, a disorder of learning. It has genetic, epigenetic and environmental influences. It is all of that and more. Addiction is a display of the brain’s astounding ability to change — a feature called plasticity — and it showcases what we know and don’t yet know about how brains adapt to all that we throw at them. “A lot of people think addiction is what happens when someone finds a drug to be the most rewarding thing they’ve ever experienced,” says neuroscientist George Koob, director of the National Institute on Alcohol Abuse and Alcoholism in Bethesda, Md. “But drug abuse is not just feeling good about drugs. Your brain is changed when you misuse drugs. It is changed in ways that perpetuate the problem.” The changes associated with drug use affect how addicts respond to drug cues, like the smell of a cigarette or the sight of a shot of vodka. Drug abuse also changes how other rewards, such as money or food are processed, decreasing their relative value. © Society for Science & the Public 2000 - 2013
By DOUGLAS QUENQUA A tiny part of the brain keeps track of painful experiences and helps determine how we will react to them in the future, scientists say. The findings could be a boon to depression treatments. The habenula (pronounced ha-BEN-you-la), a part of the brain less than half the size of a pea, has been shown in animal studies to activate during painful or unpleasant episodes. Using M.R.I.s to produce powerful brain scans, researchers at University College London tracked the habenulas in subjects who were hooked up to electric shock machines. The subjects were presented with a series of photographs, some of which were followed by increasingly strong shocks. Soon, when the subjects were shown pictures associated with shocks, their habenulas would light up. “The habenula seems to track the associations with electric shocks becoming stronger and stronger,” said Jonathan Roiser, a neuroscientist at the college and an author of the study, published in The Proceedings of the National Academy of Sciences. The habenula appeared to have an effect on motivation, too. The subjects had been asked to occasionally press a button, just to show they were awake. They were much slower to do so when their habenula was active. In fact, the more slowly they responded, the more reliably their habenulas tracked associations with shocks. In animals, the habenula has been shown to suppress production of dopamine, a chemical that drives motivation. Perhaps, the researchers say, an overactive habenula can cause the feelings of impending doom and low motivation common in people with depression. © 2014 The New York Times Company