Duke Research Blog

Following the people and events that make up the research community at Duke.

Category: Behavior/Psychology (Page 1 of 16)

Quantifying Sleepiness and How It Relates to Depression

Sleep disturbance is a significant issue for many individuals with depressive illnesses. While most individuals deal with an inability to sleep, or insomnia, about 20-30% of depressed patients report the opposite problem – hypersomnia, or excessive sleep duration.

David Plante’s work investigates the relationship between depressive disorders and hypersomnolence. Photo courtesy of sleepfoundation.org

Patients who experience hypersomnolence report excessive daytime sleepiness (EDS) and often seem to be sleep-deprived, making the condition difficult to identify and poorly researched.

David Plante’s research focuses on a neglected type of sleep disturbance: hypersomnolence.

David T. Plante, MD, of the University of Wisconsin School of Medicine and Public Health, studies the significance of hypersomnolence in depression. He said the condition is resistant to treatment, often persisting even after depression has been treated, and its role in increasing risk of depression in previously healthy individuals needs to be examined.

One problem in studying daytime sleepiness is quantifying it. Subjective measures include the Epworth sleepiness scale, a quick self-report of how likely you are to fall asleep in a variety of situations. Objective scales are often involved processes, such as the Multiple Sleep Latency Test (MSLT), which requires an individual to attempt to take 4-5 naps, each 2 hours apart, in a lab while EEG records brain activity.

The MSLT measures how long it takes a person to fall asleep. Individuals with hypersomnolence will fall asleep faster than other patients, but determining a cutoff for what constitutes healthy and what qualifies as hypersomnolence has made the test an inexact measure. Typical cutoffs of 5-8 minutes provide a decent measure, but further research has cast doubt on this test’s value in studying depression.

The Wisconsin Sleep Cohort Study is an ongoing project begun in 1988 that follows state employees and includes a sleep study every four years. From this study, Plante has found an interesting and seemingly paradoxical relationship: while an increase in subjective measures of sleepiness is associated with increased likelihood of depression, objective measures like the MSLT associate depression with less sleepiness. Plante argues that this paradoxical relationship does not represent an inability for individuals to report their own sleepiness, but rather reflects the limitations of the MSLT.

Plante proposed several promising candidates for quantitative measures of excessive daytime sleepiness. One candidate, which is already a tool for studying sleep deprivation, is a ‘psychomotor vigilance task,’ where lapses in reaction time correlate with daytime sleepiness. Another method involves infrared measurements of the dilation of the pupil. Pupils dilate when a person is sleepy, so this somatic reaction could be useful.

High density EEG allowed Plante to identify the role of disturbed slow wave sleep in hypersomnolence.

Another area of interest for Plante is the signs of depressive sleepiness in the brain. Using high density EEG, which covers the whole head of the subject, Plante found that individuals with hypersomnolence experience less of the sleep cycle most associated with restoration, known as slow wave sleep. He identified a potential brain circuitry associated with sleepiness, but emphasized a need for methods like transcranial magnetic stimulation to get a better picture of the relationship between this circuitry and observed sleepiness.

By Sarah Haurin

Detangling Stigma and Mental Illness

Can you imagine a world without stigma? Where a diagnosis of autism or schizophrenia didn’t inevitably stick people with permanent labels of “handicap,” “abnormal,” “disturbed,” or “dependent”?

Roy Richard Grinker can. In fact, he thinks we’re on the way to one.

It’s a subject he’s studied and lectured on extensively—stigmas surrounding mental health conditions, that is. His expertise, influence, and unique insight in the field led him to April 12, where he was the distinguished speaker of an annual lecture commemorating Autism Awareness Month. The event was co-sponsored by the Duke Center for Autism and Brain Development, the Duke Institute for Brain Sciences, and the Department of Cultural Anthropology.

Roy Richard Grinker was the invited speaker to this year’s annual Autism Awareness Month commemorative lecture. Photo credit: Duke Institute for Brain Sciences

Grinker’s credentials speak to his expertise. He is a professor of Anthropology, International Affairs, and Human Sciences at George Washington University; he has authored five books, several New York Times op-eds, and a soon-to-be-published 600-page volume on the anthropology of Africa; he studied in the Democratic Republic of the Congo as a Fulbright scholar in his early career; and, in the words of Geraldine Dawson, director of the Center for Autism and Brain Development, “he fundamentally changed the way we think about autism.”

Grinker began with an anecdote about his daughter, who is 26 years old and “uses the word ‘autism’ to describe herself—not just her identity, but her skills.”

She likes to do jigsaw puzzles, he said, but in a particular fashion: with the pieces face-down so their shape is the only feature she can use to assemble them, always inexplicably leaving one piece out at the end. He described this as one way she embraces her difference, and a metaphor for her understanding that “there’s always a piece missing for all of us.”

Grinker and Geraldine Dawson, director of the Center for Autism and Brain Development, pose outside Love Auditorium in the minutes before his talk. Source: Duke Institute for Brain Sciences

“What historical and cultural conditions made it possible for people like Isabel to celebrate forms of difference that were a mark of shame only a few decades ago?” Grinker asked.  “To embrace the idea that mental illnesses are an essential feature of what it means to be human?”

He identified three processes as drivers of what he described as the “pivotal historical moment” of the decoupling of stigma and mental illness: high-profile figures, from celebrity talk-show hosts to the Pope, speaking up about their mental illnesses instead of hiding them; a shift from boxing identities into racial, spiritual, gender, and other categories to placing them on a spectrum; and economies learning to appreciate the unique skills of people with mental illness.

This development in the de-stigmatization of mental illness is recent, but so is stigma itself. Grinker explained how the words “normal” and “abnormal” didn’t enter the English vocabulary until the mid-19th century—the idea of “mental illness” had yet to make its debut.

“There have always been people who suffer from chronic sadness or had wildly swinging moods, who stopped eating to the point of starvation, who were addicted to alcohol, or only spoke to themselves.” Grinker said. “But only recently have such behaviors defined a person entirely. Only recently did a person addicted to alcohol become an alcoholic.”

Grinker then traced the development of mental illness as an idea through modern European and American history. He touched on how American slaveowners ascribed mental illness to African Americans as justification for slavery, how hysteria evolved into a feminized disease whose diagnoses became a classist tool after World War I, and how homosexuality was gradually removed from the Diagnostic and Statistical Manual of Mental Disorders (DSM) by secretly gay psychiatrists who worked their way up the rankings of the American Psychiatric Association in the 1960s and 70s.

Source: Duke Institute for Brain Sciences

Next, Grinker described his anthropological research around the world on perceptions of mental illness, from urban South Korea to American Indian tribes to rural villages in the Kalahari Desert. His findings were wide-ranging and eye-opening: while, at the time of Grinker’s research, Koreans viewed mental illness of any kind as a disgrace to one’s heritage, members of Kalahari Desert communities showed no shame in openly discussing their afflictions. Grinker told of one man who spoke unabashedly of his monthly 24-mile walk to the main village for antipsychotic drugs, without which, as was common knowledge among the other villagers, he would hear voices in his head urging him to kill them. Yet, by Grinker’s account, they didn’t see him as ill — “a man who never hallucinates because he takes his medicine is not crazy.”

I could never do justice to Grinker’s presentation without surpassing an already-strained word limit on this post. Suffice it to say, the talk was full of interesting social commentary, colorful insights into the history of mental illness, and words of encouragement for the future of society’s place for diversity in mental health. Grinker concluded on such a note:

“Stigma decreases when a condition affects us all, when we all exist on a spectrum,” Grinker said. “We see this in the shift away from the categorical to the spectral dimension. Regardless, we might need the differences of neurodiversity to make us, humans, interesting, vital, and innovative.”

Post by Maya Iskandarani

Better Butterfly Learners Take Longer to Grow Up

Emilie Snell-Rood studies butterflies to understand the factors that influence plasticity.

The ability of animals to vary their phenotypes, or physical expression of their genes, in different environments is a key element to survival in an ever-changing world.

Emilie Snell-Rood, PhD, of the University of Minnesota, is interested in why this phenomena of plasticity varies. Some animals’ phenotypes are relatively stable despite varying environmental pressures, while others display a wide range of behaviors.

Researchers have looked into how the costs of plasticity limit its variability. While many biologists expected that energetic costs should be adequate explanations for the limits to plasticity, only about 30 percent of studies that have looked for plasticity-related costs have found them.

Butterflies’ learning has provided insight into developmental plasticity.

With her model of butterflies, Snell-Rood has worked to understand why these researchers have come up with little results.

Snell-Rood hypothesized that the life history of an animal, or the timing of major developmental events like weaning, should be of vital importance in the constraints on plasticity, specifically on the type of plasticity involved in learning. Much of learning involves trial and error, which is costly – it requires time, energy, and exposure to potential predators while exploring the environment.

Additionally, behavioral flexibility requires an investment in developing brain tissue to accommodate this learning.

Because of these costs, animals that engage in this kind of learning must forgo reproduction until later in life.

To test the costs of learning, Snell-Rood used butterflies as a subject. Butterflies require developmental plasticity to explore their environments and optimize their food finding strategies. Over time, butterflies get more efficient at landing on the best host plants, using color and other visual cues to find the best food sources.

Studying butterfly families shows that families that are better learners have increased volume in the part of the brain associated with sensory integration. Furthermore, experimentally speeding up an organism’s life history leads to a decline in learning ability.

These results support a tradeoff between an organism’s developmental plasticity and life history. While this strategy is more costly in terms of investment in neural development and energy investment, it provides greater efficacy in adaptation to environment. However, further pressures from resource availability can also influence plasticity.

Looking to the butterfly model, Snell-Rood found that quality nutrition increases egg production as well as areas of the brain associated with plasticity.

Understanding factors that influence an animal’s plasticity is becoming increasingly important. Not only does it allow us to understand the role of plasticity in evolution up to this point, but it allows us to predict how organisms will adapt to novel and changing environments, especially those that are changing because of human influence. For the purposes of conservation, these predictions are vital.

By Sarah Haurin

ECT: Shockingly Safe and Effective

Husain is interested in putting to rest misconceptions about the safety and efficacy of ECT.

Few treatments have proven as controversial and effective as electroconvulsive therapy (ECT), or ‘shock therapy’ in common parlance.

Hippocrates himself saw the therapeutic benefits of inducing seizures in patients with mental illness, observing that convulsions caused by malaria helped attenuate symptoms of mental illness. However, depictions of ECT as a form of medical abuse, as in the infamous scene from One Flew Over the Cuckoo’s Nest, have prevented ECT from becoming a first-line psychiatric treatment.

The Duke Hospital Psychiatry program recently welcomed back Duke Medical School alumnus Mustafa Husain to deliver the 2018 Ewald “Bud” Busse Memorial Lecture, which is held to commemorate a Duke doctor who pioneered the field of geriatric psychiatry.

Husain, from the University of Texas Southwestern, delivered a comprehensive lecture on neuromodulation, a term for the emerging subspecialty of psychiatric medicine that focuses on physiological treatments that are not medication.

The image most people have of ECT is probably the gruesome depiction seen in “One Flew Over the Cuckoo’s Nest.”

Husain began his lecture by stating that ECT is one of the most effective treatments for psychiatric illness. While medication and therapy are helpful for many people with depression, a considerable proportion of patients’ depression can be categorized as “treatment resistant depression” (TRD). In one of the largest controlled experiments of ECT, Husain and colleagues showed that 82 percent of TRD patients treated with ECT were remitted. While this remission rate is impressive, the rate at which remitted individuals experience a relapse into symptoms is also substantial – over 50% of remitted individuals will experience relapse.

Husain’s study continued to test whether a continuation of ECT would be a potentially successful therapy to prevent relapse in the first six months after acute ECT. He found that continuation of ECT worked as well as the current best combination of drugs used.

From this study, Husain made an interesting observation – the people who were doing best in the 6 months after ECT were elderly patients. He then set out to study the best form of treatment for these depressed elderly patients.

Typically, ECT involves stimulation of both sides of the brain (bilateral), but this treatment is associated with adverse cognitive effects like memory loss. Using right unilateral ECT effectively decreased cognitive side effects while maintaining an appreciable remission rate.

After the initial treatment, patients were again assigned to either receive continued drug treatment or continued ECT. In contrast to the previous study, however, the treatment for continued ECT was designed based on the individual patients’ ratings from a commonly used depression scaling system.

The results of this study show the potential that ECT has in becoming a more common treatment for major depressive disorder: maintenance ECT showed a lower relapse rate than drug treatment following initial ECT. If psychiatrists become more flexible in their prescription of ECT, adjusting the treatment plan to accommodate the changing needs of the patients, a disorder that is exceedingly difficult to treat could become more manageable.

In addition to discussing ECT, Husain shared his research into other methods of neuromodulation, including Magnetic Seizure Therapy (MST). MST uses magnetic fields to induce seizures in a more localized region of the brain than available via ECT.

Importantly, MST does not cause the cognitive deficits observed in patients who receive ECT. Husain’s preliminary investigation found that a treatment course relying on MST was comparable in efficacy to ECT. While further research is needed, Husain is hopeful in the possibilities that interventional psychiatry can provide for severely depressed patients.

By Sarah Haurin 

First Population Health Conference Shares Energy, Examples

Logo: Population Health at Duke‘Population Health’ is the basis of a new department in the School of Medicine, a byword for a lot of new activity across campus , and on Tuesday the subject of a half-day symposium that attempted to bring all this energy together.

For now, population health means a lot of different things to a lot of different people.

The half-day symposium drew an overflow crowd of faculty and staff. (photo – Colin Huth)

“We’re still struggling with a good definition of what population health is,” said keynote speaker Clay Johnston, MD, PhD, dean of the new Dell School of Medicine in Austin, Texas. Smoking cessation programs are something most everyone would agree is taking care of the population outside of the clinic. But improved water quality? Where does that fit?

“We have an intense focus on doctors and their tools,” Johnston said. Our healthcare system is optimized for maximum efficiency in fee-for-service care, that is, getting the most revenue out of the most transactions. “But most of health is outside the clinic,” Johnston said.

Perhaps as a result, the United States pays much more for health care, but lives less well, he said. “We are noticeably off the curve,” when compared to health care costs and outcomes in other countries.

This graphic from a handout shared at the conference shows how population health spans the entire university.

This graphic from a handout shared at the conference shows how population health spans the entire university.

As an example of what might be achieved in population health with some re-thinking and a shift in resources, the Dell School went after the issue of joint pain with input from their engineering and business schools. Rather than diagnosing people toward an orthopedic surgery – for which there was a waitlist of about 14 months – their system worked with patients on alternatives, such as weight loss, physical therapy and behavioral changes before surgery. The 14-month backlog was gone in just three months. Surgeries still happen, of course, but not if they can be comfortably delayed or avoided.

“Payment for prevention needs serious work,” Johnston said. “You need to get people to buy into it,” but in diabetes or depression for example, employers should stand to gain a lot from having healthier employees who miss fewer days, he said.

Health Affairs Chancellor Eugene Washington commented several times, calling the discussion “very interesting and very valuable.” (photo -Colin Huth)

Other examples flowed freely the rest of the afternoon. Duke is testing virtual ‘telemedicine’ appointments versus office visits. Evidence-based prenatal care is being applied to try to avoid expensive neonatal ICU care. Primary care and Emergency Department physicians are being equipped with an app that helps them steer sickle cell patients to appropriate care resources so that they might avoid expensive ED visits.

Family practitioner Eugenie Komives, MD, is part of a team using artificial intelligence and machine learning to try to predict which patients are most likely to be hospitalized in the next six months. That prediction, in turn, can guide primary care physicians and care managers to pay special attention to these patients to help them avoid the hospital. The system is constantly being evaluated, she added. “We don’t want to be doing this if it doesn’t work.”

Community health measures like walkability and grocery stores are being mapped for Durham County on a site called Durham Neighborhood Compass, said Michelle Lyn, MBA, chief of the division of community health. The aim is not only to see where improvements can be made, but to democratize population health information and put it in peoples’ hands. “(Community members) will have ideas we never could have thought of,” Lyn said. “We will be able to see change across our neighborhoods and community.”

Patient input is key to population health, agreed several speakers. “I don’t think we’ve heard them enough,” said Paula Tanabe, PhD, an associate professor of nursing and medicine who studies pain and sickle cell disease.  “We need a bigger patient voice.”

Health Affairs Chancellor and Duke Health CEO Eugene Washington, MD, has made population health one of the themes of his leadership. “We really take seriously this notion of shaping the future of population health,” he said in his introductory remarks. “When I think of the future, I think about how well-positioned we are to have impact on the lives of the community we serve.”

Lesley Curtis, PhD, chair of the newly formed Department of Population Health Sciences in the School of Medicine, said Duke is creating an environment where this kind of work can happen.

“I, as an organizer of this, didn’t know about half of these projects today!” Curtis said. “There’s so much going on at an organic level that the challenge to us is to identify what’s going on and figure out how to go forward at scale.”

Post by Karl Leif Bates

How a Museum Became a Lab

Encountering and creating art may be some of mankind’s most complex experiences. Art, not just visual but also dancing and singing, requires the brain to understand an object or performance presented to it and then to associate it with memories, facts, and emotions.

A piece in Dario Robleto’s exhibit titled “The Heart’s Knowledge Will Decay” (2014)

In an ongoing experiment, Jose “Pepe” Contreras-Vidal and his team set up in artist Dario Robleto’s exhibit “The Boundary of Life Is Quietly Crossed” at the Menil Collection near downtown Houston. They then asked visitors if they were willing to have their trips through the museum and their brain activities recorded. Robleto’s work was displayed from August 16, 2014 to January 4, 2015. By engaging museum visitors, Contreras-Vidal and Robleto gathered brain activity data while also educating the public, combining research and outreach.

“We need to collect data in a more natural way, beyond the lab” explained Contreras-Vidal, an engineering professor at the University of Houston, during a talk with Robleto sponsored by the Nasher Museum.

More than 3,000 people have participated in this experiment, and the number is growing.

To measure brain activity, the volunteers wear EEG caps which record the electrical impulses that the brain uses for communication. EEG caps are noninvasive because they are just pulled onto the head like swim caps. The caps allow the museum goers to move around freely so Contreras-Vidal can record their natural movements and interactions.

By watching individuals interact with art, Contreras-Vidal and his team can find patterns between their experiences and their brain activity. They also asked the volunteers to reflect on their visit, adding a first person perspective to the experiment. These three sources of data showed them what a young girl’s favorite painting was, how she moved and expressed her reaction to this painting, and how her brain activity reflected this opinion and reaction.

The volunteers can also watch the recordings of their brain signals, giving them an opportunity to ask questions and engage with the science community. For most participants, this is the first time they’ve seen recordings of their brain’s electrical signals. In one trip, these individuals learned about art, science, and how the two can interact. Throughout this entire process, every member of the audience forms a unique opinion and learns something about both the world and themselves as they interact with and make art.

Children with EEG caps explore art.

Contreras-Vidal is especially interested in the gestures people make when exposed to the various stimuli in a museum and hopes to apply this information to robotics. In the future, he wants someone with a robotic arm to not only be able to grab a cup but also to be able to caress it, grip it, or snatch it. For example, you probably can tell if your mom or your best friend is approaching you by their footsteps. Contreras-Vidal wants to restore this level of individuality to people who have prosthetics.

Contreras-Vidal thinks science can benefit art just as much as art can benefit science. Both he and Robleto hope that their research can reduce many artists’ distrust of science and help advance both fields through collaboration.

Post by Lydia Goff

Understanding the Link Between ADHD and Binge Eating Could Point to New Treatments

 

Binge eating disorder is the most prevalent eating disorder in the United States. Infographic courtesy of Multi-Service Eating Disorders Association

With more than a third of the adult population of the United States meeting criteria for obesity, doctors are becoming increasingly interested in behaviors that contribute to these rates.

Allan Kaplan is interested in improving treatment of binge eating disorder.

Allan Kaplan, MD, of the University of Toronto, is interested in eating disorders, specifically binge eating disorder, which is observed in about 35 percent of people with obesity.

Binge eating disorder (BED) is a pattern of disordered eating characterized by consumption of a large number of calories in a relatively short period of time. In addition to these binges, patients report lack of control and feelings of self-disgust. Because of these patterns of excessive caloric intake, binge eating disorder and obesity go hand-in-hand, and treatment of the disorder could be instrumental in decreasing rates of obesity and improving overall health.

In addition to the health risks associated with obesity, binge eating disorder is associated with anxiety disorders, affective disorders, substance abuse and attention deficit hyperactivity disorder (ADHD) – in fact, about 30 percent of individuals with binge eating disorder also have a history of ADHD.

Binge eating disorder displays a high comorbidity with mood and affective disorders. Infographic courtesy of American Addiction Centers.

ADHD is characterized by inability to focus, hyperactivity, and impulsivity, and substance abuse involves cravings and patterns of losing control followed by regret. These patterns of mental and physiological sympoms resemble those seen in patients with binge eating disorder. Kaplan and other researchers are linking the neurological patterns observed in these disorders to better understand BED.

Researchers have found that the neurological pathways become active when a patient with binge eating disorder is provided with a food-related stimulus. Individuals with the eating disorder are more sensitive to food-related rewards than most people. Researchers have also identified a genetic basis — certain genes make individuals more susceptible to reward and thus more likely to engage in binges.

Because patients with ADHD exhibit similar neurological patterns, doctors are looking to drugs already approved by the FDA to treat ADHD as possible treatments for binge eating disorder. The first of these approved drugs, Vyvanse, has proven not much better than the traditional form of treatment, cognitive behavioral therapy, a form of talk therapy that aims to identify and correct dysfunctions in behavior and thought patterns that lead to disordered behaviors.

Another drug, however, proved promising in a study conducted by Kaplan and his colleagues. The ADHD drug methylphenidate, combined with CBT, led to significant clinical outcomes — pateints engaged in less binges and cravings and body mass index decreased. Kaplan argues that the most effective treatment would reduce binges, treat physiological symptoms like obesity, improve psychological disturbances like low self-esteem, and, of course, be safe. So far, the combination of psychostimulants like methylphenidate and CBT have met these criteria.

Kaplan emphasized a need to make information about binge eating disorder and its treatments more available. Most individuals currently being treated for BED do not obtain treatment knowing they have an eating disorder — they are usually diagnosed only after seeking help with obesity-related health issues or help in weight loss. Making clinicians more familiar with the disorder and its associated behaviors as well as encouraging patients to seek treatment could prove instrumental in combating the current healthcare issue of obesity.

By Sarah Haurin

Mice, motor learning, and making decisions

Advanced imaging techniques allow neuroscientists to better understand how the motor outputs we observe are created in the brain.

Early understandings of the brain viewed it as a black box that takes sensory input and generates a motor response, with the in-between functioning of the brain as a mystery.

Takaki Komiyama is curious about how the brain produces the stereotypical movements characteristic of motor learning.

Takaki Komiyama of the University of California, San Diego is curious about the relationship between sensory input, motor output, and what happens in between. “What fascinates me the most is the flexibility of this dynamic… this flexibility of the relationship between the environment and the brain is the key element of my research,” Komiyama said to an audience of Duke neuroscience researchers.

Komiyama and his lab have designed experiments to watch how the brain changes as mice learn. Specifically, they train mice to complete a lever-pushing task in response to an auditory stimulus and then use an advanced imaging technique to watch the activity of specific populations of neurons.

Komiyama based his experimental design on a hallmark of motor learning: An “expert” mouse will hear the auditory stimulus and produce a motor response that is exactly the same each time. Komiyama’s team was curious about how these reproducible movements are learned.

Focusing on the primary motor cortex, called M1 for short, Komiyama observed many different neuronal firing patterns as the mouse learned the motion of lever-pushing. As the mouse ventured into “expert” territory, usually after about two weeks of training, this variation was replaced by an activity pattern that is the same from trial to trial. In addition to being consistent, this final pattern starts earlier after the stimulus and takes less time to complete than earlier patterns. In other words, during learning, the brain tries out different pathways for the goal action and then converges on the most efficient way of producing the desired response.

Komiyama then turned his focus to M2, the secondary motor cortex, which he observed to be one of the last areas activated during early learning trials but one of the first activated during late trials. To test M2’s role in learning, Komiyama inactivated the region in trained mice and subjected them to the same stimulus-motor response trial.

The mice with inactivated M2’s missed more trials, took longer to initiate movement, and completed the lever pushing less efficiently. Essentially, the mice behaved as if they had never learned the movement, suggesting that M2 is crucial for coordinating learned motor behavior.

In addition to identifying crucial patterns of motor learning, Komiyama and his team are working to understand decision making. After designing a more complex lever-pushing task that required pushing a joystick in different directions depending on the visual stimulus, Komiyama observed the mice’s accuracy plateaued around 60%.

The mice’s internal biases prevented them from achieving better results in the visual stimuli task.

Komiyama hypothesized that this pattern of inaccuracy could be explained by the mice’s internal biases from previous trials’ outcomes. He designed a statistical model that incorporated the previous trials’ outcomes. With further testing, the model accurately predicted the mice’s wrong choices.

The posterior parietal cortex (PPC) is an area of the brain that has been found to be involved in decision making tasks. Komiyama observed neurons in the PPC that predicted which direction the mice would push the joystick. In addition to being active before the motor response during trials, these neurons were also active in the time between trials.

Seeing this as a neural correlate for internal biases, Komiyama hypothesized that inactivating this region would decrease the influence of bias on the mice’s choices. Sure enough, inactivating the PPC led to more accurate responses in the mice, thus confirming the PPC as a neural source of bias.

 By Sarah Haurin

How A Bat’s Brain Navigates

Most of what we know about how the hippocampus, a region of the brain associated with memory formation and spatial representations, comes from research done on rodents. Rat brains have taught us a lot, but researchers in Israel have found an interesting alternative model to understanding how the hippocampus helps mammals navigate: Bats.

The Egyptian fruit bat proved the perfect subject for studies of mammalian navigation.

Weizmann Institute neurophysiologist Nachum Ulanovsky, PhD, and his team have looked to bats to understand the nuances of navigation through space. While previous research has identified specific cells in the hippocampus, called place cells, that are active when an animal is located in a specific place, there is not much literature describing how animals actually navigate from point A to point B.

Nachum Ulanovsky

Ulanovsky believes that bats are an ingenious model to study mammalian navigation. While bats have the same types of hippocampal neurons found in rats, the patterns of bats’ neurons’ firings more closely match that of humans than rats do.

Ulanovsky sought to test how bats know where they are going. Using GPS tracking equipment, his team found that wild bats that lived in a cave would travel up to 20 kilometers to forage fruit from specific trees. Night after night, these bats followed similar routes past perfectly viable food sources to the same tree over and over again.

The understanding of hippocampal place cells firing at specific locations doesn’t explain the apparent guided travel of the bat night after night, and other explanations like olfactory input do not explain why the bats fly over good food sources to their preferred tree.

The researchers designed an experiment to test how bats encode the 3D information necessary for this navigation. By letting the bats fly around and recording brain activity, Ulanovsky and team found that their 3D models are actually spherical in shape. They also found another type of hippocampal cells that encode the orientation the bat is facing. These head direction cells operate in a coordinate system that allows for a continuity of awareness of its orientation as the animal moves through space.

http://www.cell.com/cms/attachment/2091916945/2076305003/gr1_lrg.jpg

Ulanovsky found bats relied on memory to navigate toward the goal.

To understand how the bats navigate toward a specific goal, the researchers devised another experiment. They constructed a goal with a landing place and a food incentive. The bat would learn where the goal was and find it. In order to test whether the bats’ ability to find the goal was memory-based, or utilized the hippocampus, the researchers then conducted trials where the goal was hidden from the bats’ view.

To test whether the bats’ relied on memory, the Ulvanosky team measured the goal direction angle, or the angle between the bat’s head orientation and the goal. After being familiarized with the location of the goal, the bats tended toward a goal-direction angle of zero, meaning they oriented themselves toward the goal even when the goal was out of sight.

Continued research identified cells that encode information about the distance the bat is from the goal, the final piece allowing bats to navigate to a goal successfully. These hippocampal cells selectively fire when the bat is within specific distances of the goal, allowing for an awareness of location over distance.

While Ulanovsky and his team have met incredible success in identifying new types of cells as well as new functions of known cells in the hippocampus, further research in a more natural setting is required.

“If we study only under these very controlled and sterile environments, we may miss the very thing we are trying to understand, which is behavior,” Ulanovsky concluded.

By Sarah Haurin

Hearing Loss and Depression Are Connected

Jessica West is a PhD candidate in sociology.

Jessica West, a PhD student in sociology at Duke, has found that hearing loss creates chronic stress but that high levels of social support – from family, friends and others – can help alleviate depression. Given that hearing loss is a growing social and physical health problem, her study suggests a need for increased vigilance regarding hearing loss among older adults, West said.

Her study was published in the November issue of Social Science & Medicine and is available here.

Here, West discusses her research.

Your research examines the correlation between hearing loss and depression. That seems a logical connection: why study it in the way you did?

Despite how common hearing loss is, it is actually quite understudied. A handful of studies have looked at the relationship between hearing loss and mental health over time, but the results from these studies are mixed: some find a relationship between hearing loss and more depressive symptoms, while others do not. On top of the mixed findings, most studies have been based overseas, and studies based in the U.S. have tended to use state-specific datasets, like the Alameda County Study, which drew from Oakland and Berkeley, CA.

I use the Health and Retirement Study, which is nationally representative of adults aged 50 and older in the U.S., and therefore more generalizable to the U.S. population.

I frame hearing loss as a physical health stressor that can impact mental health, and that social support can alter this relationship by preventing a person from experiencing stress or reducing the severity of a reaction to it. To the best of my knowledge, this is the first paper to link hearing loss to health outcomes in this way.

What might surprise people about your findings?

More than one-fifth of the people in my sample have fair to poor hearing (23.12% or 1,405 people in the first wave). Hearing loss is really common in the U.S.

Also, I found that social support is most beneficial in easing the burden of hearing loss among people with significant hearing loss. Overall, this suggests that hearing loss is a chronic stressor in people’s lives and that responses to this stressor will vary by the level of social resources that people have available to them.

What does ‘social support’ mean in real terms? What can the family and friends do for a person with hearing loss to help them?

For people with hearing loss, it’s important that they feel able to lean on, talk to, and rely on family, friends, spouses or partners, and children. And going a step further, people with hearing loss need to know that these important people in their lives truly understand the struggles they face. What this means is that people with hearing loss can benefit quite a lot from having a network of people that they feel comfortable discussing things with or reaching out to when needed.

Do people with hearing loss have adequate mental health resources or care available to them?

My research shows that social support is really important for people with hearing loss. One suggestion I make in my paper is that audiologic – or hearing — rehabilitation programs could include educational training for significant others, like spouses or friends, to emphasize the importance of supporting people with hearing impairment. Audiologists, primary care physicians, family, and friends are all key resources that could be targeted in such rehabilitation programs.

 What is your next project related to hearing loss?

 I am currently working on several projects related to hearing loss. In one, I am looking at the relationship between an individual’s hearing loss and his/her spouse’s mental health outcomes. Few population-based studies have examined the relationship between hearing loss and spousal mental health longitudinally, so I hope this study will shed light on the experience of spousal disability within marriages.

Another project I am working on looks at hearing loss from a life course perspective. In other words, I am looking at people who self-reported hearing loss before the age of 16 and seeing how their hearing loss influenced their marriages, academics and careers. A better understanding of how early life hearing loss influences later life outcomes has implications for earlier identification of hearing loss and/or the use of assistive technology to help people remain socially, academically, and economically engaged.

CITATION: West, Jessica S. 2017. “Hearing Impairment, Social Support, and Depressive Symptoms among U.S. Adults: A Test of the Stress Process Paradigm.” Social Science & Medicine 192(Supplement C):94-101.

 Read the paper 

Guest post by Eric Ferreri, News and Communications

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