The limbic system of the human body regulates the subconscious, as well as the instinctive, or ‘primitive’ urges of humans.
When these primal urges are activated, the limbic system takes charge as the primary brain area for processing sensory stimuli. The urges such as anger, fear, thirst, hunger, drives, emotions, and instincts, are processed and controlled through a conscious decision of the individual that originates from the dedicated parts of the cerebral cortex of the brain.
Being a part of the limbic system, the amygdala (Gr. amygdala – almond) is an almond-shaped area of the brain responsible for the translation of the feelings of anger, fear, or pleasure, and anxiety stimuli, as well as aggression.
In addition, the amygdala largely contributes to the processing of motivation and memories.
Where Is the Amygdala Located in the Human Brain?
The amygdala is the brain area that is responsible for deriving emotional responses by processing and translating sensory stimuli. It is located in the temporal lobe, positioned right in front of the hippocampus.
Anatomy and Structure of the Amygdala
Amygdala consists of two parts, located in each of the temporal lobes. Clusters of neurons, i.e. a group of nuclei comprise this area of the brain. Among these brain structures are the following nuclei:
- The basolateral complex of nuclei
- Cortical nucleus
- Medial nucleus
- Central nucleus
- Intercalated cell clusters
Functions of the Basolateral Complex of Amygdala’s Nuclei
The basolateral complex is made up of lateral, basal, and accessory-basal nuclei of the amygdala. They are also major outputs of information to the cerebral cortex.
Due to this anatomical function, the basolateral complex of amygdala nuclei plays a great role in decision making, memory, and attention.
Triggering fear response is also regarded as one of the primary functions of the basolateral complex of nuclei in the amygdala. Through activation of this ‘fear system’, the individual is alerted to avoid injury or pain. Thus, this complex of nuclei has a vital role in survival.
Functions of the Cortical Nucleus of Amygdala
This nucleus of the amygdala is the neural output of the information translated from the sensory stimuli as intense negative emotions, especially fear and aggression.
From here, they are transmitted to the anterior cingulate cortex, orbitofrontal cortex, and the prefrontal cortex in order to be further processed and controlled.
Functions of the Medial Nucleus of Amygdala
The neurons of the medial nucleus of the amygdala receive, process, and transmit the sensory information from the olfactory pathways to the hypothalamic nuclei. The medial nucleus is in charge of the basic innate emotions – fear, sadness, happiness, surprise, anger, and disgust.
Also, it plays a vital role in forming the reproduction and defense responses of the brain, based on the corresponding sensory stimuli.
Functions of the Central Nucleus of Amygdala
This is the main output of the information processed by the neurons in the amygdala. This nucleus takes the central position within the amygdala and is responsible for receiving sensory signals from the pain receptors, as well as in the processing of pain information.
Functions of Intercalated Cell Clusters
The intercalated cell clusters of the amygdala play a great role in both the storage and formation of memory.
Located between the basolateral and central nuclei of the amygdala, they contribute to the regulation of emotion by inhibiting the output of these two clusters of neurons.
What Is the Primary Function of the Amygdala?
Being a part of the limbic system, the amygdala regulates many aspects of memory and emotion, as well as our survival instincts and motivation. This brain area links the intensely powerful emotions with associated memorable events, such as fear, anger, sadness, or joy.
It also plays a key role in forming new memories, specifically related to fear. This is the reason why the amygdala is also labeled as the brain’s center of fear.
The amygdala is also responsible for the perception of sensory information as emotions of anger, fear, or sadness.
How Does the Amygdala Affect Our Behaviour?
By coordinating the responses of the stimuli received from the world that surrounds us, the amygdala helps us translate and define our emotions, at the same time enabling us to produce a corresponding emotional response.
The process of biological evolution has assigned a strong survival quality to each of the emotions. Yet, all of the emotions can have a destructive quality, as well.
By way of illustration, fear can alarm our defenses in a dangerous situation, but it can also hold us back and inhibit our progress.
The Role of the Amygdala in Emotions
As the main processing center of the brain for emotions, the amygdala helps us create corresponding emotional responses to the developed emotions.
Namely, after processing the information gained from the senses, or the stored memories of similar experiences, the amygdala triggers fear-related responses or assigns positive emotions to the stimuli.
The Role of the Amygdala in Fear
The sensory stimuli received by the visual cortex are processed in the thalamus. From here, and with the help of the amygdala, they play a role in increasing and focusing our attention as a response to fear.
The role of the visual cortex in the process is also to create fearful impressions of our surroundings (people with expressions of fear on their faces, approaching danger, etc.). This triggers the reaction in the amygdala and increases attention and arousal. It also processes these stimuli in order to derive a corresponding answer to them.
The amygdala is rich in cortisol receptors. Cortisol is the body’s main stress hormone which serves as our built-in system in charge of alerting us when we’re in some kind of danger. It triggers the ‘fight or flight’ response when the amygdala signals a stressful or intimidating situation, i.e. fear.
The Role of the Amygdala in Motivation
Even though its primary function includes the regulation and control of negative emotions, such as fear, anxiety, aggression, stress, and anger, the amygdala also takes part in the regulation of the positive emotions triggered by appetitive stimuli.
What Are Appetitive Stimuli?
Appetitive stimuli is a type of positive reinforcement in the form of pleasant and wanted stimulus (or action) that precedes consummatory behavior.
Since the amygdala regulates hunger, thirst, and sexual desire as well, this type of stimuli indicates the urge and desire for consummation.
The individuals who are conditioned with the appetitive stimulus (such as water, bodily pleasures, or food) will approach the available stimulus with great desire.
What Happens When the Amygdala Is Dysfunctional?
Damage to the amygdala can lead to various neuropsychiatric disorders. Also, it can result in diseases associated with the physiological processes of the brain or specific areas of the cerebral cortex.
Most of these disorders are in a close relationship with the feelings regulated by the amygdala, such as fear, anxiety, etc. Hence, the individuals that have suffered damage to the amygdala report the following medical conditions, disorders, or diseases:
- General anxiety disorder
- Panic attack disorder
- Post-traumatic stress disorder
- Bipolar disorder
- Stress
- Urbach-Wiethe disease
- Drug abuse
- Addictions of various kinds (alcohol, bodily pleasures, food, medicine abuse)
- Autism
- Memory disorders
What Happens When Someone Naturally Has No Fear At All?
The role of the amygdala’s in the processing of fear is indisputable. But, as this emotion can save our lives in some given events of approaching danger, damage to the amygdala can lead to a person feeling no fear at all. This, too, can be potentially dangerous.
Urbach-Wiethe disease is a genetic disorder characterized by increased accumulation of calcium salts in temporal lobes. This affects the amygdala, which results in loss of the ability to feel fear, since this brain area is particularly designated to translate this emotion.
The individuals affected with the Urbach-Wiethe disease report no fear of death, public speaking, dangerous animals (e.g. snakes, alligators), no increase of heart rate in stressful situations such as gun or knife threat of attack. In short, these patients approach everything they should avoid as potentially life-endangering.
Conclusion
The amygdala is a subcortical structure, located centrally to the limbic system. The group of neurons which comprise this brain area react to stimuli that trigger a reward or punishment expectation, rather than associating the stimuli with reward or punishment.
Being labeled as the brain’s center of fear, the amygdala plays a vital role in our survival by raising alert whenever there is a life-endangering event in our surroundings. Upon translating the sensory information as dangerous, the amygdala commands elevation of our heart rate and blood pressure, thus making us more alert and ready to protect ourselves.
The stimulation of the amygdala further triggers the release of the cortisol hormone, which additionally increases our focus in dangerous situations.
On the other hand, the amygdala also has an active role in the formatting of cognitive processes, such as memory, attention, and decision making.
Fun Facts
Did you know?
- The proper functioning of the amygdala is vital for our survival. Namely, it’s in charge of regulation and control of our survival instincts by triggering the ‘fight or flight’ reaction in cases when we perceive a given situation as life-threatening or dangerous.
- After the amygdala translates the fear stimuli, it commands us to either run or fight for our lives.
- By taking deep and slow breaths we can calm the activity of our amygdala, thus increasing our state of relaxation. This is very useful during a panic attack or when a stressful situation is looming.
- The feeling of fear helps us survive the dangers and threats upon our lives. However, we have been born with two innate fears – the fear of loud sounds, and the fear of falling.
- Adrenal glands are responsible for making the stress hormone cortisol in our bodies.
- Cortisol boosts our energy level in a potentially dangerous situation, thus preparing us to endure the stress and mobilize our body’s capacities for protection.
- Anger is the strongest emotion of the entire range of emotions. It can overshadow happiness, even love at some times. Think, for example, of the time after you’ve had an argument with someone you love – the first emotion you feel is anger after the argument, while the emotions of love are overshadowed at that moment.
- Whenever we see an emotion play out on a person’s face, the amygdala becomes activated and responds with a corresponding emotional answer to these visual stimuli.
- We can stop the anxiety triggered by the amygdala by slowing down and focusing on our thoughts, thus allowing the frontal cortex to take over the regulation of the sensory stimuli. In this way, we can choose a more rational response to the emotional trigger for our anxiety.
- The feeling of fear can lead to impairment of the formation of long term memories. It can also cause damage to the hippocampus, which further aggravates the control and regulation of the unpleasant emotion.
- Even though fear is an unpleasant emotion, the lack of ability to feel it could be life-endangering.