03 Jun Study Explores How Does Amygdala Process Fear Memory in Your Brain
“Emotional regulation” towards the various changes in the environment is an important adaptive human function.
It helps in regulating our physiological and behavioral responses to a circumstance and surviving the situation.
Out of all the emotion regulation pathways, the most important pathway for both the mental and physical well-being of humans is how the brain processes fear.
According to reports and scientific evidence, the regulatory pathway for fear involves the following steps:
- Extinction
- Cognitive regulation
- Active coping
- Reconsolidation
And the major component of the brain involved in the majority of these steps is the amygdala, an almond-shaped structure, the hub of fear processing.
The following sections throw more light on how does the amygdala process fear.
Amygdala and Fear Regulation
Amygdala is an almond-shaped structure located in the temporal lobe of the brain as a set of nuclei that act as the initiatory point for the processing of the emotion—fear.
It forms a major part of a circuit. And, according to studies, it regulates fear expression by forming a fearful memory and interacting with other parts of the brain.
The main function of the amygdala hence becomes supporting the ability of a human brain to identify a potential stimulus for fear in order to avoid danger.
It does so by identifying, storing, and expressing fear.
What Does the Amygdala Do?
As a general process, the sense of fear first begins in the brain further spreading to the entire body for a complete defensive action.
The initiation point of this whole cycle is the amygdala. It detects the stimuli for fear to activate different areas in the body for fight or flight action.
One such amygdala function example is the sight of a dangerous animal. This triggers the release of hormones and activates the sympathetic nervous system, resulting in:
- Hyperalert senses
- Dilation of pupils of the eye
- Dilation of bronchi with high respiratory rate
- Heart functions heightened with increased heart rate
- Hypertension
- Increase in the transportation of glucose to skeletal muscles
However, the amygdala doesn’t perceive threats all on its own. It interacts with the hippocampus and prefrontal cortex to sense the strength of danger.
If the hippocampus and prefrontal cortex don’t sense a real danger, they activate inhibitory pathways for the amygdala, preventing the fear response.
The section right below has more details.
How Does the Amygdala Process Fear?
The amygdala works through the following pathways:
#1. Recognition
Amygdala has a lateral nucleus that encodes the stimulus by sensing the sensory inputs.
When a fear stimulus is present, it excites the central nucleus that controls passive pathways of expression of a response.
#2. Expression
The central nucleus regulates the brainstem and hypothalamus to control the expression of fear.
The lateral nucleus, on the other hand, also regulates the basal nucleus that projects to the nucleus accumbens in the striatum.
Since the striatum is responsible for decision-making, it helps in active coping.
Other than the recognition and expression, the amygdala is responsible for storing fearful memories like Childhood trauma and memories to help in avoiding future dangers.
How does the amygdala control fear and how is it able to carve it into memory can be understood better with the following studies.
Hence, we look at the following studies clarifying what does the amygdala do with fear after the active coping mechanism.
Study Showing Formation of Fear Memories – Amygdala Emotional Memory Pathway
Studies find that your behavior and your responses towards fear are because of the formation of fear memories in the amygdala.
This is further explained by the changes in the frequency of brain wave oscillation because of the stimulation of neurons in the amygdala through norepinephrine.
Study – Role of Stress Hormone in Initiating the Fear Circuit
A team of neuroscientists at Tulane University School of Science and Engineering and Tufts University School of Medicine studied the formation of memories in the amygdala.
According to the key details of the study findings, the stress hormone, norepinephrine, is responsible for fear processing.
The neurotransmitter excites neurons in the amygdala that generates repetitive electrical discharge patterns.
These patterns change the normal resting state of the amygdala to an aroused state, causing the formation of memories.
Scientific Model of the Study
The research explored the mechanisms behind the regulation of behavioral states towards fear.
It largely focused on showing how Gq activation and the activation of the noradrenaline receptors in the basolateral amygdala cause changes in the oscillations of the brain, causing fear memory recall.
The basis of the study was the role of BLA (Basolateral Amygdala) theta- and gamma frequency in the regulation of fear expression.
Since the regulation of these frequencies is controlled by parvalbumin-expressing interneurons in the BLA, any neuromodulation signals affecting them could trigger the regulation.
Hence, Gq neuromodulation of these neurons was studied.
This revealed:
- Molecular and cellular changes due to Gq modulation affect the activity of the interneurons in the amygdala. This causes emotional brain state transitions.
- The neuromodulation caused tuning of the frequencies facilitating the expressions.
- Since the activations were because of stimulation of the endogenous noradrenaline receptors, its role in fear expression is seen as vital.
Though conducted on mice, the study hence brought to notice how changes in the frequency of the theta and gamma waves of the amygdala can cause fear memory formation.
This helps us identify danger and also helps in avoiding the danger by initiating the circuit of fear regulation.
However, the biology of the amygdala is not just helpful in emotional salience but also goes beyond that.
Amygdala Role in Memory
Amygdala is popular for its key functions:
- Regulating fight or flight
- Managing stress and fear responses
But its role in memory goes beyond just remembering the fear stimulus.
Based on the amygdala’s role in memorizing fear stimulus, the following studies were done:
Study – Effect of DBS on Amygdala
Using Deep Brain Stimulation (DBS) by implanting electrodes deep into the brains of rats, the basolateral complex of the amygdala was stimulated.
This stimulation aimed to see if during the learning process the rats were able to memorize whatever the study controllers wanted them to remember.
Results showed that stimulation helped rats remember the images shown during the learning process.
Human Effects
Inspired by the study on rats, a similar study was carried out on 14 epilepsy patients.
The results showed that using DBS to stimulate the amygdala improved recognition and memory among worst memory problem patients.
Aggression and Amygdala
The amygdala, as we read above, is an important part of the brain for emotional regulation.
But other than regulating your expression of fear, it also controls how aggressive you can get.
Groves and Schlesinger (1982) found that when the amygdala was surgically removed in violent patients, their aggression was reduced to a great extent.
Animal studies also show that removing amygdala lowers the aggressive behavior.
Hence, the amygdala can trigger aggressive behavior among organisms too.
Conclusion
Neurobiology helps identify the roles of different parts of the brain in regulating emotions.
A recent study found amygdala, the flight and fight controlling portion of your brain, is involved in more than regulating the expression of emotions.
Earlier, we knew that the amygdala regulates the expression of fear, but a recent report highlighted its role in storing fear memories too.
This helps people identify a threat that had previously stimulated fear in them and hence helps avoid danger.
It also helps in tagging different emotions as memories for a better response from the body towards such emotions.
Yet, we still need more studies for an extensive explanation of how the amygdala can regulate your responses.
But that’s it for today. Please share your thoughts with us down in the comments section.
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