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  1. #1
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    Science of "shutting down"?

    Logic takes charge when emotional confusion reigns

    Finding may lead to development of tailored treatments for anxiety

    Daily life requires that people cope with distracting emotions - from the basketball player who must make a crucial shot amidst a screaming crowd, to a salesman under pressure delivering an important pitch to a client. Columbia University Medical Center researchers have now identified an emotional control circuit in the human brain which keeps emotionally intense stimuli from interfering with mental functioning. These results significantly enhance our understanding of the neurobiology underlying psychiatric disorders involving emotional control, such as post traumatic stress disorder (PTSD) or depression.

    The research employed a novel test in which subjects were forced to detect and resolve attentional conflict created by emotionally powerful stimuli. Brain activity was monitored using functional magnetic resonance imaging (fMRI) that can detect moment-to-moment changes in neural activity. fMRI is a version of the widely-used clinical MRI scanning technique.

    The study, published in the Sept 21, 2006 issue of Neuron, was led by a Columbia University Medical Center M.D./Ph.D. student, Amit Etkin, who explained that, "Tremendous knowledge exists about how our brains deal with cognitive distractions, but we know very little about how we deal with emotional distractions. This is something we constantly do in our everyday lives, otherwise we would be overwhelmed by every emotional trigger we encounter."

    The current findings extend on a previous Neuron paper (Dec 16, 2004) in which Drs. Etkin, Kandel and Hirsch found that anxious individuals show more activity in the amygdala, a central brain region involved in the processing of negative emotions, when unconsciously perceiving fearful stimuli. When these stimuli were perceived consciously, however, the amygdalas of subject with both high and low levels of anxiety responded similarly.

    Dr. Hirsch explained that this previous finding suggested that subjects were somehow able to control their conscious emotional responses, but that their unconscious responses may be more automatic. "Following the discovery of the amygdala's role in fear response, we decided to explore the finer points of the neurocircuitry of fear - how it is regulated and controlled in the brain," said Dr. Hirsch.

    To study emotional regulation, Dr. Etkin collaborated with Tobias Egner, Ph.D., a post-doctoral fellow in Dr. Hirsch's lab, who has used fMRI to study non-emotional forms of attentional control. Subjects were asked to identify the facial expressions in photos shown to them as either happy or fearful. Across each face were the words FEAR or HAPPY, and were either congruent or conflicting from the facial expressions. When the word and face clashed, subjects experienced an emotional conflict, which slowed their performance and made them less accurate in identifying facial expressions.

    Using a clever behavioral trick, however, the researchers were able to discriminate between brain circuitry that detected this emotional conflict from circuitry that resolved this conflict. They found that the amygdala generates the signal telling the brain that an emotional conflict is present; this conflict then interferes with the brains ability to perform the task. The rostral anterior cingulate cortex, a region of the frontal lobe, was activated to resolve the conflict. Critically, the rostral cingulate dampened activity in the amygdala, so that the emotional response did not overwhelm subjects' performance, thus achieving emotional control.

    It appears the brain lets the amygdala process straightforward emotions. But when the emotional waters are muddy, the rostral anterior cingulate cortex steps in and takes the reins.

    "This paper adds important regulatory circuit information about the fear response in the amygdala," said Dr. Hirsch. "For example, if someone is walking on an empty street at night and hears a loud banging sound in the near distance, the amygdala would immediately light up. But instead of always running in the opposite direction from the sound, the rostral cingulate determines if action is needed or not. For example, if it was a car door slamming, the rostral cingulate would shut down the amygdala."

    "Based on these findings, tailored treatments may be developed in the future based on the biology of the person's disease," said Dr. Kandel. "For example, we may be able to tailor treatment for an individual depending upon whether anxiety is primarily manifested in the amygdala's response to unconscious threat, or primarily in the ability of the rostral cingulate to control conscious emotion."

    "Interestingly, several studies have found that rostral cingulate activity predicts whether a depressed patient will respond to medication," said Dr. Etkin. People with PTSD, as well as those whose depression is resistant to treatment, show lowered rostral cingulate activity during emotional processing. "Indeed, lower rostral cingulate activity prior to treatment actually predicts a poor response to antidepressant therapy," the researchers note.

    "The findings from the current study, therefore, may help explain why more rostral cingulate activity may be beneficial. They suggest that elevated amygdalar activity and exaggerated behavioral interference may be due to deficient amygdalar inhibition by the rostral cingulate, which leads to an inability to deal with emotional conflict. The capacity for recruitment of the rostral cingulate may thus determine how well an individual can cope with the intrusion of negative emotional stimuli or mental content," they concluded.

    Source: Etkin A, Egner T, Peraza DM, Kandel ER, Hirsch J. Resolving Emotional Conflict: A Role for the Rostral Anterior Cingulate Cortex in Modulating Activity in the Amygdala. Neuron. 2006 Sep 21;51(6):871-882. [Abstract]

  2. #2
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    Re: Science of "shutting down"?

    Brain Helps Keep Emotions at Bay

    WEDNESDAY, Sept. 20 (HealthDay News) — A new study may reveal how people function amidst distracting emotions.

    Published in the Sept. 21 issue of Neuron, the findings suggest the human brain is able to prevent emotions from interfering with mental functioning.

    Researchers from Columbia University Medical Center in New York City asked volunteer participants to indicate by pressing a button whether a face image was happy or fearful, while ignoring “fear” and “happy” labels written across each face.

    The labels were either “congruent” (e.g., happy face, “happy” label) or “incongruent” (e.g., happy face, “fear” label). The incongruent labels were designed to represent a conflict between emotional and cognitive stimuli.

    During the tests, the researchers used functional magnetic resonance imaging to determine what parts of the brain were active.

    They found that when the participants were exposed to the incongruent labels, activity of the amygdala — the brain’s center for processing emotional events — was inhibited by the anterior cingulated cortex — the brain’s center for neural processing.

    The researchers speculated that their findings may help explain why people who suffer from post-traumatic stress disorder (PTSD) or depression may be unable to control emotional intrusion into their thoughts. They pointed out that the brains of people with PTSD and depression may be less able to inhibit the amygdala during emotional processing.

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