1. Study suggests veterans with PTSD have increased ‘fight or flight’ response

    May 24, 2017 by Ashley

    From the Physiological Society press release:

    Young veterans with combat-related post-traumatic stress disorder (PTSD) have an increased ‘fight or flight’ response during mental stress, according to new findings published this week in the Journal of Physiology.

    The team at Emory University School of Medicine, led by Dr Jeanie Park, believe that this contributes to the increased risk of high blood pressure and heart disease in PTSD patients.

    PTSD is prevalent in both military and civilian populations. The lifetime prevalence of PTSD in US adults is 7.8% and around 14% in post-9/11 veterans. PTSD patients are known to have a higher risk for developing high blood pressure and cardiovascular disease.

    The researchers also found that veterans with PTSD had higher adrenaline levels and less control of their heart rate in response to blood pressure changes. While previous studies have suggested that the sympathetic nervous system- the ‘fight or flight’ response- of veterans is overactive, this study was the first to measure this increased activity directly and provide a potential mechanism behind this response.

    Dr Park and her team took these measurements while the participants experienced two types of mental stress. First-person war images and sounds shown through virtual reality goggles recreated mental stress related to PTSD. Mental arithmetic elicited mental stress un-related to PTSD.

    They studied the physiology of post-9/11 veterans, 14 of whom had PTSD and 14 who did not. They measured blood pressure, performed an electrocardiogram (EKG), and recorded sympathetic nerve activity directly in real-time using electrodes placed inside a large nerve. This technique is called microneurography and is considered the gold-standard method for assessing sympathetic nervous system activity in humans.

    Commenting on the study, Dr Park said: ‘To protect patients against high blood pressure and heart disease, we need to first understand how their physiology malfunctions. We can then identify potential treatments.’

    ‘This study looked specifically at veterans with combat-related PTSD, so the findings do not necessarily apply to non-veterans with PTSD, nor to patients with non-combat-related PTSD,’ she added.


  2. Study suggests cognitive behavioral therapy could help stress in sport

    May 21, 2017 by Ashley

    From the Leeds Beckett University press release:

    Cognitive behavioural therapy (CBT) could be a powerful tool to help elite sportspeople improve their performance by handling stress more effectively, new research has found.

    The study, by Leeds Beckett and Loughborough Universities, is the first to show that CBT can change how high-level athletes respond to organizational stress within their sport, and that this can have significant benefits for their emotions and performance.

    Sport psychology researcher, Dr Faye Didymus, worked with four high-level female hockey players over nine months, using a CBT technique called cognitive restructuring to help them identify what put them under pressure, understand how they responded emotionally, and then consider more helpful alternative responses. The results were immediate: things that they had viewed as threats, players began to see instead as challenges, resulting in more positive emotions and higher satisfaction with their performance.

    Dr Didymus, from the Carnegie Research Institute at Leeds Beckett University, said: “Cognitive restructuring can help people take control of what they think about stress, which is incredibly empowering. This is particularly true in sport where individuals have to perform under pressure, either alone or as part of a team. CBT has been used in health and business settings to improve individuals’ wellbeing and performance but it’s wider use in sport is long overdue.”

    The players were from the Investec Women’s Hockey League, which, although amateur, includes the top teams in England, with players selected from the League to compete at international level. Although most players are also working or studying full-time, teams can have up to five training sessions and two competitive matches each week.

    Selection and deselection from their team and the presence of England selectors at a big game were some of the causes of stress — known as ‘stressors’ — identified by the players during the research. Others included lack of communication from the coach, issues with teammates or training, large crowds at matches and poor umpire decisions.

    The players were assessed before the CBT began to identify those who would be most likely to benefit from the programme. Each player then took part in an in-depth personalised programme of CBT to help them understand their current thoughts about stress, associated emotions, and how these might be changed by CBT. For example, for a player who was thinking ‘I must play well or I will ruin my chance of selection,’ an alternative would be suggested, such as: ‘If I play well, I’ve a good chance of being selected,’ which views selection as a challenge rather than a threat. Players would then be asked to think about how this different thought might change their feelings or emotions.

    Over the nine months, the players moved from considering these alternative responses theoretically and in discussion with Dr Didymus to coming up with their own ‘alternatives’ and integrating those into their thought processes whenever they trained or competed.

    An immediate positive impact was seen on all of the stress-related variables that Dr Didymus targeted: the players started to view more stressors as challenges than threats, positive emotions predominated, and the players’ performance satisfaction began to increase. When the players were assessed three months after the programme, these benefits had been maintained.

    One of the players who took part in the research explained her experiences as follows: ‘If I’m thinking about stressors as a challenge not a threat then I play better. I learnt how to see things as a challenge, which has helped my performance.’ Another said: ‘I practice thought adjustment in training like I do my hockey so it comes naturally in matches and nine times in ten I’m more satisfied with how I perform.’

    Given the success of the trial, Dr Didymus believes that the programme she’s developed should now be adapted and tested across a range of sports: “Ours was a small trial in one sport so we now need to see if this can replicated in other sports with the same positive effects,” she said. “We’d also like to integrate objective measures of performance within future trials, and to look at how improving individuals’ responses to stress can benefit the team as a whole.”


  3. Study suggests pet dogs help kids feel less stressed

    May 20, 2017 by Ashley

    From the University of Florida press release:

    Pet dogs provide valuable social support for kids when they’re stressed, according to a study by researchers from the University of Florida, who were among the first to document stress-buffering effects of pets for children.

    Darlene Kertes and colleagues tested the commonly held belief that pet dogs provide social support for kids using a randomized controlled study — the gold standard in research.

    “Many people think pet dogs are great for kids but scientists aren’t sure if that’s true or how it happens,” Kertes said. Kertes reasoned that one way this might occur is by helping children cope with stress. “How we learn to deal with stress as children has lifelong consequences for how we cope with stress as adults.”

    For their study, recently published in the journal Social Development, the researchers recruited approximately 100 pet-owning families, who came to their university laboratory with their dogs. To tap children’s stress, the children completed a public speaking task and mental arithmetic task, which are known to evoke feelings of stress and raise the stress hormone cortisol, and simulates real-life stress in children’s lives. The children were randomly assigned to experience the stressor with their dog present for social support, with their parent present, or with no social support.

    “Our research shows that having a pet dog present when a child is undergoing a stressful experience lowers how much children feel stressed out,” Kertes said . “Children who had their pet dog with them reported feeling less stressed compared to having a parent for social support or having no social support.”

    Samples of saliva was also collected before and after the stressor to check children’s cortisol levels, a biological marker of the body’s stress response. Results showed that for kids who underwent the stressful experience with their pet dogs, children’s cortisol level varied depending on the nature of the interaction of children and their pets.

    “Children who actively solicited their dogs to come and be pet or stroked had lower cortisol levels compared to children who engaged their dogs less,” said Kertes, an assistant professor in the psychology department of UF’s College of Liberal Arts and Sciences. “When dogs hovered around or approached children on their own, however, children’s cortisol tended to be higher.”

    The children in the study were between 7 to 12 years old.

    “Middle childhood is a time when children’s social support figures are expanding beyond their parents, but their emotional and biological capacities to deal with stress are still maturing,” Kertes explained. “Because we know that learning to deal with stress in childhood has lifelong consequences for emotional health and well-being, we need to better understand what works to buffer those stress responses early in life.”


  4. Study expands understanding of how the brain encodes fear memory

    May 19, 2017 by Ashley

    From the UC Riverside press release:

    Research published by scientists at the University of California, Riverside on “fear memory” could lead to the development of therapies that reduce the effects of post-traumatic stress disorder (PTSD).

    To survive in a dynamic environment, animals develop adaptive fear responses to dangerous situations, requiring coordinated neural activity in the hippocampus, medial prefrontal cortex (mPFC), and amygdala – three brain areas connected to one another. A disruption of this process leads to maladaptive generalized fear in PTSD, which affects 7 percent of the U.S. population.

    Jun-Hyeong Cho, an assistant professor of cell biology and neuroscience and Woong Bin Kim, a postdoctoral researcher in Cho’s lab, have now found that a population of hippocampal neurons project to both the amygdala and the mPFC, and that it is these neurons that efficiently convey information to these two brain areas to encode and retrieve fear memory for a context associated with an aversive event.

    The study, which appeared in the May 10 print issue of the Journal of Neuroscience, is the first to quantify these “double-projecting” hippocampal neurons and explain how they convey contextual information more efficiently for fear responses, compared to hippocampal neurons that project only to either the mPFC or the amygdala.

    “This study, done using a mouse model, expands our understanding of how associative fear memory for a relevant context is encoded in the brain,” said Cho, the lead author of the study and a member of the UCR School of Medicine’s Center for Glial-Neuronal Interactions, “and could inform the development of novel therapeutics to reduce pathological fear in PTSD.”

    To visualize the double-projecting hippocampal neurons, Cho and Kim used a tracing method in which hippocampal neurons that project to different brain areas were labeled with fluorescence proteins with different colors. The pair also developed a novel approach of electrophysiological recordings and optogenetics to examine how exactly the double-projecting neurons connected to the mPFC and amygdala. (These experimental approaches can be used to examine other brain areas that project to multiple targets.)

    “We were surprised to find that as much as 17 percent of hippocampal neurons that projected to the amygdala or the mPFC were, in fact, double-projecting neurons,” Cho said. “Although previous studies demonstrated the existence of double-projecting hippocampal neurons, neuroscientists largely ignored them when studying the role of neural pathways between the hippocampus, amygdala and mPFC in contextual fear learning.”

    Cho explained that the acquisition (encoding) and retrieval of contextual fear memory requires coordinated neural activity in the hippocampus, amygdala and mPFC. The hippocampus encodes context cues, the amygdala stores associations between a context and an aversive event, and the mPFC signals whether a defensive response is appropriate in the present context.

    Context is broadly defined as the set of circumstances around an event. In contextual fear conditioning, experimental subjects are placed in an emotionally neutral context (such as a room) and presented an aversive stimulus (such as an electrical shock). Then, they learn to associate the context with the aversive event, and show fear responses (such as freezing behavior) when placed subsequently in that context.

    “Our study suggests that double-projecting hippocampal neurons can facilitate synchronized neural activity in the mPFC and amygdala that is implicated in learned fear,” he said. “It is by modulating the activity of the mPFC and basal amygdala that these double-projecting hippocampal neurons contribute to the acquisition and retrieval of fear memory for a context associated with an aversive event.”

    Cho also explained that multiple projections from single neurons appear to be a general feature of the neural circuits in the brain and could promote synchronized neural activity and long-term changes in the efficiency of neural communication.

    The study came about when, a few years ago, Cho and Kim were selectively labeling and stimulating hippocampal neurons that project to the mPFC, and examining how this manipulation affects fear memory formation in mice. When they carefully examined the brain tissue, they found that labeled hippocampal neurons also projected to the amygdala.

    “We initially thought there was something wrong with our experiments,” Kim, the postdoctoral researcher, said. “But, when we repeated the experiments, the same pattern was observed consistently. We realized that this could be an exciting finding that may account for how contextual information is processed and conveyed between brain areas for the formation of fear memory for the context associated with an aversive event.”

    Next, to better understand the role of double-projecting hippocampal neurons in fear learning and memory, Cho and Kim plan to selectively silence these neurons and examine how this manipulation impacts the formation of fear memory for a context associated with an aversive event.


  5. PTSD, certain prescriptions for PTSD may raise risk for dementia

    May 15, 2017 by Ashley

    From the American Geriatrics Society press release:

    Researchers are discovering that post-traumatic stress disorder (PTSD) is a significant risk factor in developing dementia. Dementia is a memory problem that affects a person’s ability to carry out usual tasks. Dementia is a leading cause of serious illness, disability, and death. It often requires care in a nursing home or other long-term care facility for people aged 65 and older.

    Until now, researchers didn’t know whether the kinds of medications used for people with PTSD could increase risks for dementia. (These medications include including antidepressants, antipsychotics, sedatives, or tranquilizers.) A new study, published in the Journal of the American Geriatrics Society, examined this connection.

    In their study, researchers examined information from 3,139,780 veterans aged 56 and older. At the beginning of the study, in 2003, the veterans were receiving health care from a Veterans Health Administration facility. Almost all the veterans were male and 82% were white.

    Of the veterans in the study, 5.4% had been diagnosed with PTSD. As the researchers looked at the data over the study’s nine-year follow-up period, they also included veterans who were diagnosed with dementia.

    Research has previously shown that veterans with PTSD are more likely to have health problems linked to a higher risk for dementia. These include traumatic brain injury, diabetes, chronic obstructive pulmonary disease (COPD), psychiatric disorders, substance abuse, and other health issues.

    In this study, researchers discovered that taking certain antidepressants, tranquilizers, sedatives, or antipsychotic medications significantly increased veterans’ risks for developing dementia compared to the risks for veterans who didn’t take such medications.

    Medicines that significantly increased dementia risk included:

    • Selective serotonin reuptake inhibitors (SSRIs)
    • Novel antidepressants
    • Atypical antipsychotics

    The increase in the risk of dementia for veterans taking the drugs was the same whether or not they were diagnosed with PTSD. (This is compared to veterans who weren’t taking these drugs.)

    What’s more, veterans who used three classes of medications were also more likely to be diagnosed with dementia whether or not they had PTSD. These medicines include:

    • Novel antidepressants
    • Serotonin-norepinephrine reuptake inhibitors (SNRIs)
    • Benzodiazepines

    The researchers noted that an interaction among these “psychoactive” drugs could potentially affect how PTSD impacts a person’s risk for developing dementia. The researchers concluded that further research should be conducted to learn more about PTSD and psychoactive drugs, including dosage, how long to take the medications, and which people could most benefit from them.


  6. Exposure to racism harms children’s health

    May 14, 2017 by Ashley

    From the American Academy of Pediatrics press release:

    New research to be presented at the 2017 Pediatric Academic Societies 2017 Meeting illustrates the unhealthy effects racism can have on children, with reported exposure to discrimination tied to higher rates of Attention Deficit Hyperactivity Disorder (ADHD), anxiety and depression, as well as decreased general health.

    Authors of the study abstract, “The Detrimental Influence of Racial Discrimination in the United States,” will present their findings on Sunday, May 7, in the Moscone Covention Center West in San Francisco. For the study, they looked at data from 95,677 participants in the 2011-12 National Survey on Children’s Health. In addition to providing physical and mental health data, caregivers of children in the survey were asked whether the child had experienced being “judged or treated unfairly” because of his or her race or ethnicity.

    After adjusting for socioeconomic status, family structure, primary language and other factors, the researchers found a significant link between exposure to racism and health. The average proportion of children reported by parents to be in “excellent health” decreased by 5.4 percent among those exposed to perceived discrimination, for example. Exposure to racism also appeared to boost the odds of ADHD by 3.2 percent.

    The biggest reduction in general health appeared among low-income, minority children, particularly Hispanic participants, said Ashaunta Anderson, MD, MPH, lead author of the study abstract and Assistant Professor of Pediatrics at the University of California, Riverside.

    Some children exposed to discrimination who were from high-income households, however, also experienced negative health effects.

    “White children with high income who experienced racial or ethnic discrimination had larger decreases in general health,” Dr. Anderson said, “while black children experiencing that combination of factors had increased rates of ADHD.”

    The study also found that children who experienced racial discrimination had twice the odds of anxiety and depression compared to children who did not experience discrimination. In turn, children with anxiety or depression had roughly half the odd of excellent general health, and four times the odds of ADHD.

    “Our findings suggest that racial discrimination contributes to race-based disparities in child health, independent of socioeconomic factors,” Dr. Anderson said, adding that coordinated efforts are needed to support children affected by discrimination with developmentally appropriate coping strategies and systems of care. In particular, she said, programs that provide positive parenting practices training and promote positive peer and role model relationships can help buffer children from the negative health effects of discrimination.


  7. ‘Narrative expressive writing’ might protect against harmful health effects of divorce-related stress

    May 13, 2017 by Ashley

    From the Wolters Kluwer Health press release:

    For people going through a divorce, a technique called narrative expressive writing — not just writing about their emotions, but creating a meaningful narrative of their experience — may reduce the harmful cardiovascular effects of stress related to marital separation, reports a study in Psychosomatic Medicine: Journal of Biobehavioral Medicine, the official journal of the American Psychosomatic Society. The journal is published by Wolters Kluwer.

    Narrative expressive writing led to improvements in heart rate and an index of the heart’s responses to stress, according to the research by psychology doctoral student Kyle J. Bourassa and colleagues of University of Arizona, Tucson. “The results suggest that the ability to create a structured narrative — not just re-experiencing emotions but making meaning out of them — allows people to process their feelings in a more adaptive way, which may in turn help improve their cardiovascular health,” said Kyle Bourassa.

    The study included 109 adults (70 women and 39 men) with a recent marital separation. Participants were randomly assigned to one of three writing exercises, performed on three occasions over several days.

    One group performed a traditional expressive writing task, with instructions to write freely about their “strongest and deepest emotions.” In a prior study by principal investigator Dr. David Sbarra, this approach seemed to increase separation-related emotional distress, particularly among participants with high psychological rumination — the tendency to persistently think about one’s mood.

    Another group performed a narrative expressive writing task, in which they created a “coherent and organized narrative” of their separation experience — culminating in describing an end of their “divorce story.” The third group was given an emotionally neutral writing task. Indicators of the body’s cardiovascular responses to stress were compared before and after the writing tasks (up to 9 months after the writing).

    Participants assigned to narrative expressive writing had a reduction in heart rate as well as an increase in heart rate variability (HRV), which measures beat-to-beat variations in heart rate. Higher HRV reflects better functioning of the body’s parasympathetic nervous system reactions to stimuli, including stress.

    These effects were moderate in size — heart rate in the narrative expressive writing group was about seven beats per minute lower than the other two groups — and were consistent across some stressful and non-stressful laboratory tasks (such as doing mental math). Blood pressure was unaffected. There was no evidence that expressive writing increased physical stress responses in people with a high degree of psychological rumination.

    Dr. Sbarra noted, “From this work, we can make two specific conclusions. First, relative to the two other conditions, narrative expressive writing caused the changes we observed in the cardiovascular biomarkers. This is a pretty striking result for just 60 minutes of writing over three days. Second, the effects of narrative writing on these health-relevant biomarkers is independent of adults’ self-reported emotional responses about their separation. Creating narrative may be good for the heart, so to speak, but this does not mean there a corresponding improvement in psychological wellbeing.”

    Divorce is a common stressor linked to increased risk for poor long-term physical and mental health. Yet few studies have evaluated interventions to lessen the health impact of divorce. Since both higher heart rate and lower HRV are linked to increased health risks, narrative expressive writing might be one way to reduce the long-term health impact of divorce.

    Dr. Sbarra also suggested caution in interpreting these findings. “To be clear, this study points to causal changes in health-relevant cardiovascular responding, not health outcomes per se. Further research will be needed to clarify the links between these biomarkers and the long-term health outcomes of people after divorce.”


  8. Retirement associated with lower stress, but only if you were in a top job

    May 10, 2017 by Ashley

    From the Oxford University Press USA press release:

    A new paper published in the Journal of Gerontology suggests that the period around retirement may widen socio-economic inequalities in stress and health.

    Poorer people, or people in low status occupations, often have poorer health and higher biological stress response levels. The socio-economic-health gradient peaks around retirement in the United States and a number of European countries. This widening in health inequalities could be a reflection of the accumulation of socio-economic disadvantages over a lifetime, with early life inequalities in health becoming magnified over the life cycle.

    Retirement, however, could potentially moderate this pattern of widening health inequalities if changes in biological stress levels during retirement differ between socioeconomic groups. Higher stress levels associated with lower status work could be mitigated by retirement.

    Cortisol is a stress hormone that follows a diurnal profile, peaking around 30 minutes after awakening, and returning to very low levels by bedtime. Stressors disrupt the diurnal profile of cortisol, resulting in elevated levels of cortisol and a flatter diurnal slope from the awakening response to bedtime. Flatter diurnal cortisol slopes are thus a key biomarker associated with higher levels of stress.

    Flatter diurnal cortisol slopes are also associated with cardiovascular mortality — a one standard deviation increase in cortisol at bedtime was associated with a doubling of the relative risk of cardiovascular mortality within 6-8 years.

    This study investigated whether workers who had recently retired had lower biological stress levels as indicated by steeper (more advantageous) diurnal cortisol slopes compared to those still working in later life.

    Data from the London based Whitehall II civil servants study were analysed. 1,143 respondents who were employed with an average age of 60 were measured from five samples collected across the day. Civil service employment grade was used to categorise people into high, middle or low grades.

    Retirement was associated with lower stress levels- those who had recently retired had steeper diurnal slopes compared to those who remained in work. But on further investigation, this apparent benefit of retirement on lowering biological stress response levels was only confined to those in high status jobs. Workers in the lowest status jobs had flatter diurnal cortisol slopes compared to those in the top jobs. And retirement increased, rather than decreased these differences in biological stress levels.

    This study has shown that British civil servants employed in the lowest status jobs had the highest levels of stress as indicated by flatter (more adverse) diurnal cortisol slopes compared to those in the highest status jobs. Socio-economic differences in cortisol levels increase, rather than decrease, around the retirement period. These biological differences associated with transitions into retirement for different occupational groups may partly explain the pattern of widening social inequalities in health in early old age.

    “It may seem counter-intuitive that stopping low status work which may be stressful does not reduce biological levels of stress, said the study’s lead author, Tarani Chandola. “This may be because workers who retire from low status jobs often face financial and other pressures in retirement. This study suggests that people’s stress levels are not just determined by immediate circumstances, but by long run factors over the course of their lives.


  9. Study suggests giving partner a massage can help relieve stress

    by Ashley

    From the British Psychological Society press release:

    Giving your partner a massage can improve both their wellbeing and yours.

    That is the key finding of research by Sayuri Naruse and Dr Mark Moss from Northumbria University that is being presented at the British Psychological Society’s Annual Conference in Brighton.

    Ms Naruse, the lead researcher, commented, “The benefits of receiving a massage from a professional are well documented, but this research shows how a similar outcome can be obtained by couples with little prior training and experience of the activity.”

    A total of 38 participants completed a three-week massage course, assessing their wellbeing via questionnaires before and after massage sessions across eight areas of physical and mental wellbeing, stress, coping and relationship satisfaction.

    The couples’ wellbeing, perceived stress and coping was positively impacted by the massage course, with none of these effects having significantly decreased at a follow up three weeks after the end of the reporting period.

    Couples also found that their physical and emotional wellbeing had significantly improved following the completion of each massage session.

    Crucially, this was equally apparent whether the participant was giving or receiving the massage.

    Of the couples who took part in the study, 91 per cent said that they would recommend mutual massage to their friends and family.

    With past research having shown that couples tend to operate as a pair when coping with stress, giving each other a massage may also help to ensure relationship stability.

    Ms Naruse added, “These findings show that massage can be a simple and effective way for couples to improve their physical and mental wellbeing whilst showing affection for one another.

    “Our data also suggests that these positive effects of a short massage course may be long lasting, as is reflected in 74 per cent of the sample continuing to use massage after the course had finished.

    “Massage is a cost effective and pleasant intervention that isn’t just for a therapeutic setting but can be easily incorporated into a healthy couple’s daily routine.”


  10. Facial expressions: How brains process emotion

    May 6, 2017 by Ashley

    From the California Institute of Technology press release:

    Have you ever thought someone was angry at you, but it turned out you were just misreading their facial expression? Caltech researchers have now discovered that one specific region of the brain, called the amygdala, is involved in making these (sometimes inaccurate) judgments about ambiguous or intense emotions. Identifying the amygdala’s role in social cognition suggests insights into the neurological mechanisms behind autism and anxiety.

    The research was done in the laboratories of Ralph Adolphs, Bren Professor of Psychology and Neuroscience and professor of biology, and collaborator Ueli Rutishauser (PhD ’08) of Cedars-Sinai Medical Center in Los Angeles and a visiting associate in biology and biological engineering at Caltech. It appears in the April 21 issue of Nature Communications.

    “We have long known that the amygdala is important in processing emotion from faces,” says Adolphs. “But now we are starting to understand that it incorporates a lot of complex information to make fairly sophisticated decisions that culminate in our judgments.”

    When looking at a face, brain cells in the amygdala fire electrical impulses or “spikes” in response. However, the role of such face cells in social cognition remains unclear. Adolphs and his group measured the activity of these cells, or neurons, in patients while they were shown images of faces expressing different degrees of happiness or fear. The subjects were also shown images of faces with more ambiguous or neutral emotions, such as moderate displeasure or muted happiness. For each type of image, subjects were asked to decide whether the face looked fearful or happy. The researchers then investigated how neurons reacted to different aspects of emotions, and how the activity of the face cells related to the decision made by the subjects.

    The researchers found that there are two groups of neurons in the amygdala that respond to facial emotions.

    One group, the emotion-tracking neurons, detects the intensity of a single specific emotion, such as happiness or fear. For example, a happiness-signaling neuron would fire more spikes if the emotion was extreme happiness, and fewer spikes if the emotion was mild happiness. Separate groups of neurons within the emotion-tracking neurons code specifically for fear or for happiness.

    The other group, the ambiguity-coding neurons, indicates the ambiguity of the perceived emotion, irrespective of the nature of that emotion.

    Showing patients images of emotionally ambiguous faces was the key to understanding how the specialized neurons in the amygdala contribute to decision making, the researchers say. The faces were so ambiguous that a patient would sometimes judge the same image to be fearful at times and happy at other times. The emotion-coding neurons indicated the subjective decision the patient made about the face.

    “Most people are familiar with feeling that a face just looks too ambiguous to really decide what emotion the person is having,” says first author and visitor in neuroscience Shuo Wang (PhD ’14). “The fact that amygdala neurons signal a decision made about a face, such as which emotion it shows, gives us important insight because it shows that the amygdala is involved in making decisions rather than simply representing sensory input.”

    In addition to recording single cells from the amygdala, the researchers also carried out a neuroimaging study using fMRI (in a separate group of participants), and additionally studied the emotion judgments of three rare subjects with lesions of the amygdala. The lesion subjects showed an abnormally low threshold for deciding when a face was fearful, and the fMRI study also showed the specific effect of emotion intensity and ambiguity in the amygdala. The study is the first to combine so many different sources of data.

    These findings also suggest a mechanistic basis for potential treatments involving the painless electrical stimulation of the amygdala, which are currently being studied in ongoing clinical trials. “Researchers at multiple institutions are currently evaluating whether deep-brain stimulation of the amygdala is effective in treating severe cases of autism or post-traumatic stress disorder,” says Rutishauser. “Patients with severe PTSD are thought to have a hyperactive amygdala, which electrical stimulation might be able to inhibit. Our findings that amygdala neurons carry signals about the subjective percept of emotions indicates a more specific reason for why such electrical stimulation might be beneficial.”