How the Amygdala Controls Emotions and Learning
The limbic system holds the power to record and remember life events. And as every event has favourable and unfavourable aspects, they trigger various emotions in us. By the virtue of this quality, the limbic system is hence responsible for the regulation and stimulation of human emotions. The three main components of this system include the amygdala brain, hippocampus, and hypothalamus.
Together these structures profoundly influence our reasoning and judgements and eventually our behaviour at an unconscious level. The proceeding sections cover the cover aspects of the amygdala brain that affect us in our everyday lives.
How to Define Amygdala?
The amygdala is a part of the limbic system that controls flight and fight responses of the body. It is well regarded as the emotional centre of the brain. In simple words, we can define amygdala as a small brain structure of grey matter in the temporal lobe of the brain, which works to regulate our emotions and motivations.
Amygdala Location
Amygdala is located in the temporal lobe of the brain. It is located just in the front of the hippocampus, in the middle of the lobes. It is in proximity to the cingulate gyrus as well. Thus, finding the amygdala location is not as complex as it may seem.
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Amygdala Structure
The amygdala is best described as almond-shaped, implying that it is oval in shape and has ends that are a bit pointed. It is a subcortical brain that consists of 13 complex nuclei and grey matter. It is best defined as a cluster of nuclei. It is more scientifically preferred to be called an amygdaloid nucleus.
Amygdala Function
It wasn’t until the 19th century that the amygdala was discovered. Several investigations are being carried out to know how the parts of the amygdala function. Nonetheless, several successive examinations show that the amygdala has the following functions:-
Evaluating the Emotional Value of Events: The amygdala determines whether any event was happy, sad, frustrating, etc. It has the ability to discern impending dangers and works on preparing the body to meet the demands of the situation. Hence, it plays an inextricable role in our judgement.
Learning: It is the amygdala that facilitates learning on the paradigms of negative or positive reinforcements.
Amygdala and Hippocampus: Since it is adjacent to the hippocampus, which stores episodic memory, the amygdala can incur changes or modifications on the memory through emotions. It can also trigger emotions through reminiscing on random objects. This can be positively used to enhance memory.
To put it in simple words, the emotional aspects of the amygdala facilitate the attachment of emotions to the episodic memory of the hippocampus. This is a classic way in which the amygdala and hippocampus are often found to be working together.
Parts of the Brain - Amygdala Pathway
Each amygdaloid nucleus receives input and sends output to multiple but distinct brain regions. These inputs and outputs are referred to as pathways, and they can be afferent or efferent depending on whether they are received or sent.
Afferent Projections -
The dorsal and medial thalamus, as well as many cortical areas such as the insula, prefrontal cortex, parahippocampal cortex, and temporal cortex, send impulses to the basolateral group of nuclei. It also receives a large number of neural fibres from the brainstem.
In any case, it is clear that all of these fibres transmit a broad range of somatosensory, visual, and optical information to the amygdala. Because it receives a large number of afferent fibres, the basolateral group of nuclei is also known as the amygdaloid zone of sensory convergence.
All of the impulses received by the basolateral group are projected to the centromedial group, where they are supposed to be arranged and then sent to various motor centres to stimulate a response to the received information. As a result, the central group is also known as the amygdaloid zone of motor divergence.
These are the Structures That Send Fibres to the Amygdala in Particular:
Olfactory bulb
Orbitofrontal cortex
Cingulate gyrus
Basal forebrain
Medial thalamus
Hypothalamus
Brainstem
Efferent Projections -
The primary function of the amygdala, as previously stated, is to modulate the activity of the hypothalamus. It accomplishes this through two major pathways: the stria terminalis and the ventral amygdalofugal pathway.
The Stria Terminalis: This pathway connects the amygdala's centromedial nucleus to the hypothalamus's ventromedial nucleus. The pathway also transports fibres to the brain's septal nuclei and thalamic regions.
In addition to efferent fibres, the stria terminalis transports fibres from these three areas back to the amygdala. Stria terminalis is important in the stress responses of many different types of organisms.
Amygdalofugal Pathway: This is the amygdala's primary efferent pathway. It originates in the amygdaloid complex's centromedial and basolateral nuclei and transports fibres to various locations throughout the nervous system.
The basolateral group's axons travel medially through the innominate substance, terminating in the hypothalamus and septal nuclei. It is known that innominate substance sends cholinergic neurons to the cortex of the brain, which is important for social behaviour modulation.
What Happens When the Amygdala Part of the Brain Obtains Damage?
The amygdala is responsible for sensing dangers and threats. Additionally, it is associated with memory and emotions. Thus damage to this part of the brain can profoundly send our lives in disarray. Some of the changes that the damage can incur are:
The intensity of emotions increases drastically.
Inability to recognise the emotion or feel it
Depression, stress or anxiety.
Irregular eating habits, which are bizarre or on the extremes.
Loss of perception such as object recognition
Memory loss.
Excessive need for stimuli.
Our mental health can bring significant changes in the amygdala. Studies have found that PTSD, depression, anxiety can cause changes in the structure of this part of the body.
Fun Facts
Amygdala has a multinuclear part of the brain. It has a total of 13 nuclei. The complex amygdala part of the brain was not found until the 19th century. And when it was discovered by the renowned Burdach in the year 1952, it was only thought to be just a little body of grey matter in the mammalian temporal lobe.
Later it was called the amygdaloid nucleus. However, today, despite thousands if not lakhs of research, neuroscientists can’t claim to have known it fully. Amygdala continues to be an enigma to date. It is this complexity of the amygdala that is often referred to as the amygdala brain.
FAQs on Amygdala: Anatomy, Functions & Pathways Explained
1. What is the amygdala and where is it located in the brain?
The amygdala is an almond-shaped cluster of specialised nuclei located deep within the temporal lobe of the brain. There are two amygdalae, one in each cerebral hemisphere. It is a key component of the limbic system, which is the part of the brain involved in our behavioural and emotional responses.
2. What are the primary functions of the amygdala?
The amygdala is a versatile processing centre with several critical functions. Its primary roles include:
- Emotional Processing: It evaluates the emotional significance of sensory information, particularly for emotions like fear, anger, and pleasure.
- Memory Formation: It helps consolidate memories by attaching emotional significance to them, making emotionally charged events more memorable.
- Fight-or-Flight Response: It acts as the brain's alarm system, identifying potential threats and signalling the hypothalamus to initiate the body's fight-or-flight response.
- Decision-Making: It influences decision-making by incorporating emotional learning from past experiences, helping us avoid potential dangers.
3. How does the amygdala process emotions like fear?
When you encounter a potentially threatening stimulus (like seeing a snake), sensory information travels rapidly to the amygdala. The amygdala assesses this information and, if it perceives a threat, it sends distress signals to the hypothalamus. The hypothalamus then activates the sympathetic nervous system and the adrenal glands, triggering the release of stress hormones like adrenaline. This leads to physiological changes such as an increased heart rate and heightened alertness, preparing the body to either confront or flee from the danger.
4. What is an 'amygdala hijack' and can you provide an example?
An 'amygdala hijack' is an immediate and overwhelming emotional reaction that is disproportionate to the actual event. It occurs when the amygdala's threat response is so strong that it bypasses the neocortex (the rational, thinking part of the brain). In this state, the amygdala takes control, leading to an impulsive action. For example, suddenly yelling at a driver who cuts you off in traffic is a classic amygdala hijack, as the emotional reaction is instantaneous and much stronger than the situation warrants.
5. What is the relationship between the amygdala and the hippocampus?
The amygdala and the hippocampus work together as a team in memory processing. The hippocampus is responsible for creating and retrieving explicit memories (the 'what, where, and when' of an event). The amygdala, on the other hand, attaches emotional significance to these memories. This collaboration ensures that memories of emotionally significant events, whether positive or negative, are stored more robustly and are easier to recall.
6. What happens if the amygdala is damaged?
Damage to the amygdala can significantly impair a person's ability to process and respond to emotions. Individuals with bilateral amygdala damage may exhibit a condition known as Klüver-Bucy syndrome. Key symptoms include a reduced ability to recognise or experience fear, difficulty in reading emotional expressions in others, and impaired decision-making, especially in situations involving risk or reward. This demonstrates the amygdala's critical role in emotional learning and survival instincts.
7. Is the amygdala only responsible for negative emotions like fear and anger?
No, this is a common misconception. While the amygdala is well-known for its central role in processing fear and threats, it is also crucial for processing positive emotions. It is involved in assigning positive value to experiences, which is fundamental for reward-based learning and motivation. The amygdala helps form positive emotional associations that guide behaviour towards pleasurable and beneficial outcomes, not just away from danger.
8. How does the amygdala contribute to the formation of emotional memories?
During an emotionally arousing event, the amygdala becomes highly active. It triggers the release of stress hormones, which in turn enhance the memory-encoding function of the hippocampus. This process essentially 'tags' the memory as important. As a result, emotional memories are often more vivid, detailed, and long-lasting than neutral memories. This is why people often have very clear 'flashbulb memories' of significant life events.
