The limbic system is the collective name for structures in the human brain involved in emotion, motivation, and emotional association with memory. Shown to play a key role in the processing of emotions, the amygdala forms part of the limbic system. The amygdala is an almond-shape set of neurons located deep in the brain's medial temporal lobe. In humans and other animals, this subcortical brain structure is linked to both fear responses and pleasure. Its size is positively correlated with aggressive behavior across species. In humans, it is the most sexually-dimorphic brain structure, and shrinks by more than 30% in males upon castration. Conditions such as anxiety, autism, depression, post-traumatic stress disorder, and phobias are suspected of being linked to abnormal functioning of the amygdala, owing to damage, developmental problems, or neurotransmitter imbalance.

FACE TO FACE
WITH THE EMOTIONAL BRAIN
by Ahmad R. Hariri & Paul J. Whalen
     Amygdala responses to the facial signals of others predict both normal and abnormal emotional states. An understanding of the brain chemistry underlying these responses will lead to new strategies for treating and predicting psychopathology.
     One of our favorite scientific studies of the past few years is a laboratory assessment of how people react to strangers. The research was conducted by Alex Todorov and colleagues at Princeton. They presented subjects with pictures of faces—many faces—that they had never seen before. All of the faces were intended to have no discernible expression, that is, they wore neutral expressions. The subjects were asked to rate how trustworthy they thought each face was based on a gut reaction. Naturally, each subject thought that some of the faces were more trustworthy-looking, some were less trustworthy-looking, and some were neutral. At the same time, the response of each subject’s amygdala—a deep brain structure—was measured using functional magnetic resonance imaging (fMRI).
     The measured responses showed some relationship with the judgments the subjects made about the faces. Specifically, the amygdala responses were greatest to faces judged to be the most untrustworthy. As cool as that is, it was not the most interesting finding.
     From the many and varied opinions of the individuals ranking the faces of strangers, Todorov and colleagues computed a mean trustworthiness rating for each face. The faces were then ordered in terms of what the group thought. This was a group rule; no one individual who was studied could possibly have known what this rule was. Yet, remarkably, the mean response of the amygdala across all subjects was positively correlated with the mean trustworthy ratings for the group of subjects. This extraordinary finding tells us that there may be fundamental rules by which our emotional brains process information and generate responses. These responses are initiated without our awareness or permission and they can form the basis of our biases and prejudices. This finding also fits well with previous data showing that the amygdala reacts to changes in subtle facial signals such as pupil dilation, and facial expression, even when subjects were not aware that these signals had occurred.
     The word “explicit” is used to define situations when we can put our experiences into words because we are aware of their occurrence. “Implicit” describes those things we do more automatically, that is, without monitoring them on a moment-to-moment basis such as motor skills like riding a bike or driving your car. We take it as a given that we have an automatic motor life. Is it then so radical to think about an automatic emotional life? Some of our immediate emotional impulses—say, in the first half second—are not entirely under our explicit control; they are implicit. Where in the brain does all this take place? While the interconnected nature of our brains makes it difficult to discern the exact networks that form the substrate of these implicit and explicit reactions, one structure that is clearly implicated is the amygdala, a highly conserved brain region buried in the temporal lobes. The amygdala is intimately involved in our implicit as well as explicit responses to emotional challenges we encounter in our environment.
     In the experiment described above, implicit cues about certain facial features appear to be tracked by the amygdala. These signals have an impact on our initial “gut” reactions concerning the relative trustworthiness of strangers. The good news from this is that you can forgive yourself your initial reactions. But then the important work begins, when you must efficiently invoke an explicit strategy to take control and produce behavior that is appropriate to the social moment.
     Automatic emotional responses make sense. We are under a constant barrage of sensory information from our external and internal worlds, which must be appropriately filtered and parsed into adaptive behaviors and physiological responses. It has been known for some time that the amygdala is critical for learning about environmental predictors of threat. Whether it is a rat in a cage learning that the tone it is hearing predicts something bad—for example, a mild shock to its feet—or a human being realizing that someone is coming up from behind them because the person in front of them just widened their eyes, it is the amygdala that monitors the environment for this particular tone or the widened eyes of a friend.
     While you might have been told that it is the “fight or flight” center of your brain, we think that it is better to think of the amygdala as one of the brain areas critical for learning about and then detecting these predictive environmental signals. The decision to fight or flee is likely made by other more complex brain systems after the amygdala has indicated that a predictive signal has been detected. That said—the amygdala does control some very initial and automatic reactions to threat. Examples include heart rate and respiration changes as well as somatomotor (movement-related) responses such as orienting and freezing in place. Freezing in the initial seconds of an emotional situation is sometimes a very good strategy and one that is invoked by rats and humans alike. If you don’t yet know whether to step left or right, better to stay put and learn a little more about your current predicament.
     Over the past decade, remarkable progress has been made in understanding the specific qualities of incoming stimuli or signals, especially those related to our social worlds that are filtered by the amygdala.
     As we have noted above, in humans the amygdala takes special note of the facial reactions of others in order to predict what will happen next. In the laboratory we directly study amygdala responses to signals of threat and safety by presenting subjects with photographs of facial expressions. Numerous laboratories have independently employed this strategy and all have shown that facial expressions, especially the expression of fear, are potent activators of the human amygdala. From the expressions of others we can glean information about their internal emotional state, their intentions, and their reaction to contextual events in the immediate environment. Facial expressions of emotion have predicted important events for us in the past, and in a brain scanner we can document some very similar responses to certain facial expressions based on these previous experiences. In this way, facial expressions are naturally conditioned stimuli.
     If the amygdala is constantly monitoring something as subtle as changes in the facial expressions of others, then it can play a pivotal role in the individual differences we see in how reactive some people are to the social signals of others compared to their peers. Implications of this for healthy interpersonal interactions are enormous. For example, if amygdala reactions were overly sensitive to the facial reactions of others, one might take a simple facial movement of a friend, one that was not intended to convey disapproval, as a certain slight.
     Aberrant amygdala reactions could play a part in exacerbating a host of psychopathologies. Indeed, numerous studies have identified abnormal amygdala responses to facial expressions across a variety of psychopathologies involving emotional dysfunction such as major depression, anxiety disorders, phobias, bipolar disorder, schizophrenia, and autism. More importantly, amygdala responses to facial expressions have been used to predict treatment outcomes in both depression and generalized anxiety disorder with lower pretreatment levels of amygdala response predicting better treatment outcomes.
Ahmad R. Hariri is Professor of Psychology and Neuroscience at Duke University and Paul J. Whalen is Associate Professor in the Department of Psychological and Brain Sciences at Dartmouth College.

BAD SCIENCE AND GOOD PUBLIC RELATIONS CREATED BIPOLAR DISORDER
     In less than a decade, from roughly 1994 to 2003, the diagnosis and treatment of bipolar disorder in children and adolescents underwent a dramatic and unwarranted increase. Before 1995 bipolar disorder was rarely diagnosed in children and adolescents; today the diagnosis is commonplace, with a forty-fold increase in the number of outpatient visits for this diagnosis in childhood. In 1995 there were 20,000 such visits; by 2003 the yearly number was 800,000! Now, nearly one-third of all children and adolescents discharged from child psychiatric hospitals have been diagnosed with bipolar disorder. Most of these diagnoses are incorrect.
     “Your Child Does Not Have Bipolar Disorder: How Bad Science and Good Public Relations Created the Diagnosis” examines this diagnostic fad through a variety of lenses. Author, Stuart L. Kaplan, MD., draws heavily on his forty years of experience as a clinician, researcher, and professor of child psychiatry, to make the argument that bipolar disorder in children and adolescents is incorrectly diagnosed and incorrectly treated.
     In this provocative book, child psychiatrist Stuart Kaplan offers a challenge to parents, mental health professionals, the drug industry, the research community, and the general public. He asserts that the soaring incidence of bipolar disorder diagnoses among children and adolescents is based on incorrect, newly created definitions of the disorder, and he marshals the evidence to back up his claim.
     Chronicling the enormous growth of bipolar diagnosis in children since 1995, Dr. Kaplan vigorously disputes the clinical and scientific bases (the "bad science") behind the diagnoses and explains the catastrophic clinical consequences. At the same time, he exposes the social and cultural dynamics that underlie this clinical fad. Dr. Kaplan discusses medications used to treat bipolar disorder and the biases that currently undermine their assessment. He concludes with specific advice for parents about managing symptoms commonly mistaken as bipolar disorder.
     As Dr. Stuart L. Kaplan explains, the dramatic rise in this particular diagnosis is not based on scientific evidence; it does not reflect any new discovery or insight about the etiology or treatment of the disorder. In fact, the opposite is the case: the scientific evidence against the existence of child bipolar disorder is so strong that it is difficult to imagine how it has gained the endorsement of anyone in the scientific community.
     In his just published book, “Your Child Does Not Have Bipolar Disorder: How Bad Science and Good Public Relations Created the Diagnosis”, Dr. Stuart Kaplan explains to parents and professionals the faulty reasoning and bad science behind the misdiagnosis of childhood bipolar disorder. He critiques the National Institute of Mental Health, academic child psychiatry, the pharmaceutical industry, and the media for their respective roles in advocating for the adoption of this diagnosis. Dr. Kaplan describes very clearly what the children and adolescents actually do have, and how it should be treated. He provides real-life clinical scenarios and describes approaches to treatment that work.
     Stuart L. Kaplan, MD has authored over 100 scientific papers, book chapters, abstracts and national and international scientific presentations. Dr. Kaplan graduated from George Washington University School of Medicine and Health Sciences (Washington, DC) in 1965, and interned at Jewish Hospital (Brooklyn, NY). He is Board Certified in Child Psychiatry and Adult Psychiatry by the American Board of Psychiatry and Neurology (ABPN) and served as an examiner for the American Board of Psychiatry and Neurology 14 times.
     Dr. Kaplan was Director of Child and Adolescent Psychiatry at the Long Island Jewish Hillside Medical Center, Executive Director of Rockland Children’s Psychiatric Center, Director of Child and Adolescent Psychiatry at Saint Louis University, Director of Child and Adolescent Psychiatry and Director of Child Psychiatry residency training at Penn State College of Medicine. Dr. Kaplan is Clinical Professor of Psychiatry at Penn State College of Medicine and also sees patients (Child Psychiatry).
Kaplan, Stuart L., MD. Your Child Does Not Have Bipolar Disorder: How Bad Science and Good Public Relations Created the Diagnosis. Greenwood Publishing Group. March 2011.

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