Function Of The Amygdala
The amygdala plays a prominent role in mediating many aspects of emotional learning and behaviour. There exist a vast array of human emotions, ranging from joy to sadness, disgust to excitement, and regret to satisfaction. Most emotions possess a valence and an intensity that reflects emotional arousal. Studies of the neural basis of emotion in animal models, including those focusing on the amygdala, typically have utilized physiological or behavioral measures that likely reflect the valence and intensity of an emotional experience.
In the early part of the 20th century, psychologist Heinrich Klüver and neurosurgeon Paul C. Bucy studied monkeys with lesions of the temporal lobe that included the amygdala and observed changes in emotional, feeding, and sexual behaviour. Subsequent studies established that the amygdala was a critical structure mediating those effects.
The Pfc And The Control Of Emotional Responses
The primary roles of the PFC appear to be the analysis of complex stimuli or situations and the control of emotional responses.
There is also increasing evidence that the PFC plays an important role in controlling anxiety and the associated stress response in rats, and that cerebral laterality is an important feature of the PFC system. Thus, in a recent study right, but not left, lesions of the ventral medial PFC were shown to have anxiolytic effects, and were also more effective in suppressing the neuroendocrine and autonomic stress response.
The Amygdala And Positive Reinforcement And Attention
The role of the amygdala is not limited to fear-conditioning and the processing of aversive stimuli. Studies in rats using food-motivated associative learning indicate that the basolateral amygdala may be involved in the acquisition and representation of positive reinforcement values . Therefore, the amygdala is probably a key structure for the integration of behavior in conflicting situations, when both potentially rewarding and aversive stimuli are present. Recent studies indicate that the human amygdala can also process both positively and negatively valenced stimuli.
Recent studies also indicate that the CeA may contribute to attentional function in conditioning, by way of its influence on basal forebrain cholinergic systems and on the dorsolateral striatum.
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How To Rewire & Retrain A Brain From Anxiety
Anxiety doesnt have to control your mind and life. Thanks to plasticity, your brain can learn new therapeutic and lifestyle practices that work to shrink the amygdala, including:
- Meditation. A regular 30-minute meditation practice once a day can help reduce the size of the amygdala, which can make it easier for you to think rationally. Focused attention, open monitoring, and loving-kindness are three of the most effective mindfulness practices to include in your meditation sessions in order to lessen anxiety.
- Exposure therapy. This type of therapy begins with you creating a list of all the things that trigger your anxiety. Instead of avoiding these things, youll expose yourself to each trigger starting with the smallest trigger first. As you become more comfortable with the things that trigger you, your anxiety-based response will decrease, helping your amygdala to decrease in size.
- Tapping your temples, cheeks, or shoulders repeatedly. According to a study published in Traumatology, this mild brain stimulation can help erase fear-based memories.
- Breathing. It may seem simple, but taking a few deep breaths is one of the easiest ways to relieve anxiety. Deep breathing also allows more oxygen into your body and brain, which helps regulate your sympathetic nervous and limbic system, home to the amygdala. Take a deep breath in, hold it, and slowly let it out until your anxiety calms down.
The Modulation Of Fear
A key current challenge is to assemble our knowledge at the level of individual structures, nuclei, and neuronal populations, to knowledge at the level of distributed large-scale networks . An emerging theme from such network concepts is that there are structures more concerned with directly orchestrating fear-related responses , and structures more concerned with context-dependent modulation. Of particular interest for the latter have been prefrontal cortices, which some schemes have partitioned into orbital and medial networks, subserving processing of emotionally salient sensory stimuli and orchestrating of visceral emotional responses, respectively and into ventromedial and dorsolateral networks related to reward processing and cognitive control . Moreover, such networks can be related to specific neurotransmitters and levels of action for pharmacological intervention . The amygdala plays a key role in mediating between brainstem and cortical levels, with specific nuclei participating in distinct networks that may be similar across species . Dissecting these networks and understanding their pharmacology, constitutes one of the main research components towards treating phobias and anxiety disorders .
Fear, the amygdala, and distance
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The Brain’s Fear Center Also Contains An Off Switch For Pain
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The Anxiety Cycle & The Brain
The brain is an intriguing organ with a miraculous ability to reason quickly and rationally. Because of the brains fast-acting processes, you tend to react to a situation before you even have time to think about what happened. For example, you smile when you receive a compliment and sigh or roll your eyes when youre frustrated. You dont think about reacting that way, you just do. Usually, this process works just fine, but constant anxiety can hijack the brains quick reaction time and make fear your automatic response.
Anxiety happens in a cycle. Every time your mind experiences a pattern of a stressful cue and an anxious response, your amygdala, the part of your brain that processes fear and threats, grows larger. The anxiety cycle occurs in 4 distinct stages:
- An anxiety-producing situation. The anxiety cycle begins the moment you encounter an uncomfortable situation that produces worry or fear. Overwhelmed by sudden emotions, your heart races and your body might sweat.
- Avoidance happens to ease the fear, worry, and rapid heartbeat. Common examples of avoidance include skipping class to avoid a presentation, using drugs or alcohol to numb feelings, and procrastinating.
- Short-term relief happens when you avoid the anxiety-producing situation. This stage can give you an immediate sense of relief and lessen the symptoms of anxiety. Unfortunately, this stage is temporary.
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Genetic And Environmental Factors
Individual differences in sensitivity to threat or stress, and particular coping or affective styles appear to be critical predisposing factors for anxiety-related disorders. Genetic and environmental factors have been implicated, and how these factors interact during development is one of the major questions addressed by recent clinical and fundamental research.
Visual And Auditory Stimuli
Initially, the visual stimuli is first received by the visual thalamus and relayed to the amygdala for potential danger. The visual thalamus also relays the information to the visual cortex and is processed to see if the stimuli poses a potential threat. If so, this information is relayed to the amygdala and the muscle contraction, increased heart rate and blood pressure begins, thus activating the sympathetic neuronal pathway. A presentation of a neutral visual stimuli has been shown to intensify the percept of fear or suspense induced by a different channel of information, such as audition. From Le Doux’s research, it shows that sound stimuli are not directly relayed from the auditory thalamus to the central nucleus.
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Defense And Coping Strategies
Fear or anxiety result in the expression of a range of adaptive or defensive behaviors, which are aimed at escaping from the source of danger or motivational conflict. These behaviors depend on the context and the repertoire of the species. Active coping strategies are used when escape from threat is possible, and the autonomic changes associated with these active strategies are mediated predominantly by sympathetic activation . This is the fight-or-flight response originally described by Cannon. Passive coping strategies, such as immobilization or freezing, are usually elicited when threat is inescapable, and are usually characterized by autonomic inhibition , and a more pronounced increase in the neuroendocrine response . This type of passive response was originally described by Engel and Schmale as a conservation-withdrawal strategy. The concept of alternative strategies itself owes much to the work of Henry and coworkers. Specific brain circuits appear to mediate distinct coping reactions to different types of stressors.,
Defensive behaviors have been studied in a large number of species, and it has recently been shown that human defensive behaviors to threat scenarios arc not unlike those seen in nonhuman mammals. The importance of risk assessment in making a proper decision about the best strategy to be used in a particular context has been emphasized.
Analyzing The Brains Fear Response In Humans
Researchers surgically inserted electrodes into the amygdala and hippocampus of nine participants, who were asked to watch scenes from horror movies.
The amygdala is an almond-shaped region in the brain, situated right next to the hypothalamus, which acts as the main center for processing emotions, emotional behavior, and motivation.
The amygdala, together with the hypothalamus and the hippocampus, form the brains limbic system , which deals with memory and emotions.
The study participants had a form of medication-resistant epilepsy. The electrode placement was done as part of the clinical evaluation of their seizure activity, and the authors reassure the readers that the electrodes were implanted solely according to the clinical needs of the patients.
Lin and team recorded the participants neural activity. As Jie Zheng, the studys first author explains, deep brain electrodes capture neurons firing millisecond by millisecond, revealing in real time how the brain attends to fearful stimuli.
The researchers found that the amygdala and the hippocampus directly exchange signals when an individual recognizes emotional stimuli.
First author Zheng explains the findings in more detail:
Lead author Lin says that the study provides direct evidence that the amygdala first extracts emotional relevance and then sends this information to the hippocampus to be processed as a memory.
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What Part Of The Brain Controls Happiness
Happiness refers to an overall state of well-being or satisfaction. When you feel happy, you generally have positive thoughts and feelings.
Imaging studies suggest that the happiness response originates partly in the limbic cortex. Another area called the precuneus also plays a role. The precuneus is involved in retrieving memories, maintaining your sense of self, and focusing your attention as you move about your environment.
A 2015 study found that people with larger gray matter volume in their right precuneus reported being happier. Experts think the precuneus processes certain information and converts it into feelings of happiness. For example, imagine youve spent a wonderful night out with someone you care about. Going forward, when you recall this experience and others like it, you may experience a feeling of happiness.
It may sound strange, but the beginnings of romantic love are associated with the stress response triggered by your hypothalamus. It makes more sense when you think about the nervous excitement or anxiety you feel while falling for someone.
As these feelings grow, the hypothalamus triggers release of other hormones, such as dopamine, oxytocin, and vasopressin.
Dopamine is associated with your bodys reward system. This helps make love a desirable feeling.
Vasopressin is similarly produced in your hypothalamus and released by your pituitary gland. Its also involved in social bonding with a partner.
Where Is The Amygdala
The amygdala is a collection of nuclei found deep within the temporal lobe. The term amygdala comes from Latin and translates to “almond,” because one of the most prominent nuclei of the amygdala has an almond-like shape. Although we often refer to it in the singular, there are two amygdalaeone in each cerebral hemisphere.
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Fear Can Become Pleasure
But why do people who love roller-coasters, haunted houses and horror movies enjoy getting caught up in those fearful, stressful moments? Because the thrill doesnt necessarily end when the ride or movie ends. Through the excitation transfer process, your body and brain remain aroused even after your scary experience is over.
During a staged fear experience, your brain will produce more of a chemical called dopamine, which elicits pleasure, says Dr. Sikora.
How The Brain Processes Emotions
When it comes to emotions, it turns out that there are regions in the brain, specifically in the limbic system, that are associated with each of the 6 main emotions.
As we all know, emotions are complex. Psychologists say that we have only 6 basic emotions, which are happiness, anger, sadness, fear, surprise, and disgust. All of our other emotions are built from the 6 basic emotions. For example, jealousy stems from a combined feeling of anger or sadness, while satisfaction can be a type of happiness.
When it comes to emotions, it turns out that there are regions in the brain, specifically in the limbic system, that are associated with each of the 6 main emotions. Emotions are actually experiences that are associated with activation of certain regions in the brain.
Emotion structures in brain
Positron Emission Tomography scanning and functional MRI studies have shown that some emotions are more likely to be associated with different regions of limbic system activity than other emotions.
1. Happiness activates several areas of the brain, including the right frontal cortex, the precuneus, the left amygdala, and the left insula. This activity involves connections between awareness and the feeling center of the brain.
2. Fear activates the bilateral amygdala, the hypothalamus and areas of the left frontal cortex. This involves some thinking , a gut feeling , and a sense of urgency typically associated with survival
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Where Do Emotions Come From
The limbic system is a group of interconnected structures located deep within the brain. Its the part of the brain thats responsible for behavioral and emotional responses.
Scientists havent reached an agreement about the full list of structures that make up the limbic system, but the following structures are generally accepted as part of the group:
- Hypothalamus. In addition to controlling emotional responses, the hypothalamus is also involved in sexual responses, hormone release, and regulating body temperature.
- Hippocampus. The hippocampus helps preserve and retrieve memories. It also plays a role in how you understand the spatial dimensions of your environment.
- Amygdala. The amygdala helps coordinate responses to things in your environment, especially those that trigger an emotional response. This structure plays an important role in fear and anger.
- Limbic cortex. This part contains two structures, the cingulate gyrus and the parahippocampal gyrus. Together, they impact mood, motivation, and judgement.
How Does The Brain Change
Just as quickly as the brain reacts and adapts to the anxiety cycle, it can also unlearn that patterned response. Thats because your brain, like your physical body, can change and adapt based on your behavior patterns. Neuroplasticity is the term that refers to the brains ability to change, adapt, and rewire itself. Neuro refers to the nerve cells that make up the brain and plasticity refers to the brains malleability or capability of changing. As nerve cell connections change and connect new nerve pathways, the brain can learn and unlearn different patterns and functions. In fact, there are two types of neuroplasticity that can cause the brain to change. These are:
- Functional plasticity, which allows an undamaged part of the brain to take over functionality that would normally take place in a part of the brain that has been damaged.
- Structural plasticity, which causes the brain to change its physical shape.
The anxious brain, through learned behavior patterns, has experienced structural plasticity, causing an enlarged amygdala. Luckily, new, healthier behavior patterns and amygdala retraining can cause structural plasticity to work in your favor and shrink the amygdala back to its original size.
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The Extended Amygdala And Anxiety
Although the amygdala is clearly involved in conditioned fear, its role in anxiety is less evident, because it is often difficult to specify the stimuli that triggers anxiety.,
Thus, lesions of the rat amygdala that suppressed fearelicited startle or freezing behavior did not affect measures of anxiety in the elevated plus-maze and shock-probe-burying tests, two classic tests of anxiety for rodents. Moreover, diazepam was effective in these tests, even in amygdala-lesioned rats, suggesting that the anxiolytic effects of benzodiazepines are not necessarily mediated by the amygdala. Recent studies in primates also suggest that the amygdala is involved in mediating some acute unconditioned fear responses in rhesus monkeys, but that it is unlikely to be a key structure regarding the dispositional behavioral and physiological characteristics of the anxious temperament.
The BNST is considered to be part of the extended amygdala. It appears to be a center for the integration of information originating from the amygdala and the hippocampus , and is clearly involved in the modulation of the neuroendocrine stress response.,
Normal Versus Pathological Anxiety
Although anxiety is a natural adaptive reaction, it can become pathological and interfere with the ability to cope successfully with various challenges and/or stressful events, and even alter body condition .
In 1926, following a major flooding disaster in Leningrad, Pavlov reported a state of chronic inhibition and learning impairment in the dogs that had been successfully trained for conditioned responses in his laboratory and had directly experienced the flood. This observation and other experiments were the basis for his later studies on experimental neuroses in dogs. Pavlov discovered large differences in dogs’ individual susceptibility to psychopathology, and attributed these differences to nervous types. He described four types analogous to the four temperaments of Hippocrates, which, according to him, resulted from the combination of three factors: the strength of the nervous system , the equilibrium between excitation and inhibition processes, and the capacity to shift from inhibition to excitation and vice versa.
Although Pavlov’s typology is outdated, it is now recognized that increased vulnerability to anxiety and its disorders is associated with particular traits or endophenotypes, ie, traits that may be intermediate in the chain of causality from genes to disease. These traits may be innate or acquired during development or through experience.
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