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The limbic System
Navneet Ahuja (Nany), Wutyi Thwe Myat (Hailey), Alexandra Cervantes ,Natasha Zahn
The chosen media item is a 3 minute documentary YouTube clip on "Amygdala Hijack". In the first few seconds of the video, Robert Allan, a clinical psychologist briefly introduces the trigger of fight or flight response when animals, including humans are in the face of dangerous situations.
Emotions associated with fight or flight response, for instance, anger or fear are activated in the primitive part of our brain called the ‘amygdala’. According to the clip, while amygdala react to a threat by trying to turn our anger or fear on, the neural structures like the prefrontal cortex attempt to switch them off.
As stated by neuroscientist Joseph LeDoux from New York University during his interview in the clip, it is impossible to control the emotional part of our brain, the amygdala (hence the name, ‘Amygdala Hijack’ – amygdala taking control of the brain). This is because; there are no real connections from the prefrontal cortex to the amygdala even though there are many communicative pathways from amygdala to the cortex.
Prior to watching this media item, we comprehend that we are fully aware of what our feelings are but that we have no complete control over our emotions. After watching this clip, we learn the reason why we have no absolute control of our emotions from the neuro-scientific perspective.
This topic is of particular interest to us since individuals have different levels of tolerance and distinct emotional reactions to stressful conditions, for instance some may get extremely angry or frightened to the point that they lose their rationales and this might lead to unfortunate, regrettable consequences. Additionally, it would be intriguing to research on current understanding on this area in neuroscience to gain insights into how to control our emotions better and tell the amygdala to cool it down.
–An ancient structure of the brain located in the medial temporal lobe.
Amygdala is a part of the li
mbic system which is mainly involved in emotional responses. The amygdala is controversially known to have sub-division according to its associated structures. The cortico-medial region that is associated with the olfactory system is known to have evolved earlier than basolateral region.
The corticomedial region contains the cortical , medial and central nuclei . The fibers from these nucleus run to and from brainstem and hypothalamus. Conversely, the newer basolateral region has connections with neocortex and consist of Basal, lateral and accessory basal nuclei.
The basolateral group receives sensory information from higher brain association areas and is connected to the thalamus via amygdalofugal pathway
However, many other research disagree with this subdivision claiming that amygdala is not a structure by its own, but an extension of a cortex (Waxman, 2010).
The amygdala nuclei receives most of its input from various association areas of cortex. The lateral nucleus of the amygdala primarily receives sensory inputs which includes all five senses (visual, auditory, somatosensory, olfactory and taste). The input from lateral nucleus travels down to the dorsal nucleus of the amygdala where all the information are being integrated. Output from the amygdala arises from either the central nucleus or striatal area. The Central nucleus controls the “emotional response” which would be expressed in the brainstem.
Nevertheless, other amygdala nucleus such as basal nuclei uses both central nucleus and Striatal area to initate output. Striatal area is claimed to control actual behavior as opposed to central nucleus for emotional expression. The connections between input and output could either be direct (rare) or indirect. The indirect route requires a connection from one nucleus to the next. For example : lateral nucleus->basal nuclei->Central neucleus. The pathway between the lateral and basal nucleus is called “intramygdala connection” (LeDoux, 2007).
Knowing that amygdala connects to both brainstem and the hypothalamus its function is to control emotions as well as other hypothalamic functions like thirst and hunger.
What is amygdala hijack ?
One of amygdala’s main functions is to prevent us from threats. As previously mentioned, it is an ancient structure that is developed for basic survival mechanism. Hadley (2010) claimed that either physical (less likely in this era) or psychological threats will activate the amygdala. Threats in this context refers to anything that might impact on our “well being” such as fear, anger or harm.
In low to moderate stress level, the prefrontal cortex calms amygdala down and consider the pros and cons of the intended behavior. However, with extreme stimulus the activation of the amygdala shuts off the prefrontal cortex function. The prefrontal cortex is the part of the brain where conscious control and decision making processes occur. Hence, when amygdala perceive stimulus as a threat, the conscious part of the brain automatically gets turned off. The following response is purely controlled by the amygdala hence the name “amygdala hijack”.
Amygdala hijack is known to be an evolutionary response to the environment where there is no time for rational thinking. Actions must be done to protect yourself from harm immediately resulting in “unthinkingly" or impulsive behaviours. Hadley (2010) proposed that up to 75% of the conscious reasoning is lost during the hijack. This conclusion was backed up by another paper by Peters (2011) who claimed that the energy sent to prefrontal cortex is greatly reduced during the hijack. Moreover, only 5% of the brain is devoted to the “present” situation whereas the rest is occupied with the past or future hassles.
During the amygdala hijack, the Hypothalamic Pituitary Adrenal axis is stimulated causing the release of cortisol and adrenalin which activates the fight/flight response. A classical increase of heart rate, shallow faster breathing and dilation of pupil are reported. These symptoms are generally presented in physical and not emotional threats (Bruno, 2011).
An interesting lecture by Goleman in YouTube clip (2010) claimed that amygdala takes over the “Right” side of the prefrontal cortex during the hijack while the left side of the prefrontal cortex usually have inhibitors for “depressogenic thoughts” . The extreme take over on either left or right side would result in severe depression or emotionless behaviours correspondingly. He also mentioned that a fair bit of information from our senses goes to the amygdala which in turn creates emotional based memories.
How the fear circuit works:
WITHIN THE AMYGDALA:
As previously mentioned, the lateral and basal nuclei of amygdala can be regarded as extentions of the cortex. The central and medial nuclei of the amygdala are considered ventral extensions of the striatum. The lateral nucleus of amygdala is the gatekeeper to the amygdala. It receives incoming signals from all the sensory systems and scans for "danger signals" or threats. Additionally, other areas of the amygdala receive the same sensory input but from different regions of the brain e.g. hearing can converge on the amygdala via different pathways and at different times, resulting in a complex picture from the brain.
Auditory information enters the lateral nucleus of the amygdala via two pathways. The first pathway from the
, sends faster, less detailed input whereas the second pathway from the auditory cortex sends slower, more detailed input.This means that we can react very quickly to potential danger signals as we can bypass the cortex and react instinctively.
Sensory Inputs going into the amygdala, rest upon both dorsal and lateral nucleus of the amygdala.
The input migrates through the ventrolateral and medial areas, which then extends into other amygdala areas. All these inputs converge in the central amygdala nucleus. The central nucleus is the output or 'action' centre of the amygdala; whereby signals for behavioural and physiological responses to fear are sent to the hypothalamus for sympathetic nervous system activation.This activation directly innervates the brain-stem which in turn bypass the cortex processing.
The amygdala is hard wired to be able to react quickly to danger signals and keep us safe. In modern days, its direct path to behavioural centres of the lower brain can cause issues with the amygdala being hijacked by unthreatening stimuli.
Despite the impression given by the video, the amygdala is relatively silent compared to other brain areas. It does not fire off many signals spontaneously, to avoid 'false alarms' and unnecessary fear response.
If neurons in the amygdala receive stress signals continously from the same stimulus such as exams, fines or workplace
they become sensitized making it easier for the amygdala to be hijacked.
The activation of the limbic system occurs prior to the prefrontal cortex resulting in the delayed cortical responses. As an example, when we see a shadow in the corner of our eye, we experience sudden fear even before the threat could be perceived as unreal.
On the cellular level,there are several neurotransmitters released into the prefrontal cortex that are responsible for activation of amygdala. These include norepinephrine, dopamine, serotonin, acetylcholine and glutamate. Glutamate being the most common neurotransmitter acts upon various amygdala receptors in respond to stress and hunger signals, perhaps providing an indication to why stress can cause unusual eating patterns.
Glutamatergic transmission, as will be discussed in the next section, is crucial in both amygdala and the prefrontal cortex- the centre of fear inhibition.
Inhibition of the amygdala
The amygdala hijacks the prefrontal cortex via glutamatergic transmission. Exposure to fear stimuli, or situations that provoke anxiety activates the amygdala, and causes a marked reduction in AMPA expression and AMPA/NMDA current activity in the prefrontal cortex, particularly the infralimbic region.
The natural inhibitory pathway from the prefrontal cortex runs from GABA inhibitory intercalated cells the infralimbic medial prefrontal cortex down to terminate between the basal amygdala and the central amygdala, effectively blocking incoming signals from reaching the 'action centre'; the central amygdala. The evolutionarily older and more potent upward inhibition or hijack of the cortex by the amygdala often outweighs this inhibitory pathway.
Various manipulations can assist in increasing the efficacy of the prefrontal inhibition. For example, potentiating GABA (an inhibitor) through the use of benzodiazepines can be a short term remedy for anxiety. Upregulating the activity of receptors such as mGluR5 in the prefrontal cortex may increase the ability of people to reason that the stimuli that provoke anxiety are not threatening and thus dampen the amygdala.
The target audience in a media presentation is very important as it forms the basis of how the presentation will be delivered. In this case it is obvious that the video is aimed at those who have at least some neuroscientific background, those interested in the topic, or someone simply wishing to learn more about the topic. With the video having a small degree of complexity, it can be seen how the clip would not be intended for someone with no scientific background at all, but would be useful for someone with very limited scientific knowledge such as a student just beginning their studies. However this form of presentation would be unlikely to have a target audience such as academics and expert in this field of research not only because it lacks depth but it is also formatted in an educational manner, whereby an expert in this field would not need to learn this, as the information should already be known to them.
Is the information appropriate for target audience and unbiased:
The information presented in this article is in fact appropriate for the intended audience, which would be a person with some but not much degree of knowledge in neuroscience. This relevance is evident in the wording of the presentation, firstly the wording is simple and spoken slowly and clearly. The scientific context is simplified through the use of many figure of speech and analogies such as “ the yellow cab driver that cut you off in traffic comes to supplant the saber tooth tiger” this simplification and the allusion to modern day events allows the audience to see the modern-day connection of the fight or flight response in a less complex manner. The information presented does not seem bias as the video is not presented in a way that favours a particular point of view, instead it is presented in a more general informative format that seeks only to meet its purpose which is to educate the audience on amygdala hijack.
The quality of the information in terms of its neuroscientific credibility:
Firstly this video was obtained from Youtube but was originally a three part documentary called “This Emotional Life” which was aired on PBS, one of the United States largest media network. Although the article presents the information in a clear and concise manner with only a small degree of complexity, which makes it easier to understand and convey its message, the most important factor of the video
Getting Control of Your Anger By Robert Allan P.H.D
should be its neuroscientific credibility. In terms of those presenting in the video, they have chosen academics who are highly regarded in their chosen fields such as clinical psychologist Dr Robert Allan and Professor of neuroscience and psychology Joseph E LeDoux from the University of New York. Both of these individuals have extensive publications and research behind them, making what they say more credible based on their academic achievements alone.
It can be agreed that the video shows neuroscientific accuracy, but does simplify some of the harder-to-understand concepts. There are references of the physiological aspects of the fight or flight response such as the release of cortisol and the stopping of the digestion of our lunch, quote; “who needs to digest lunch when you are about to become lunch” these quotes simplify certain aspects of the physiology of the fight or flight response in order for the intended audience to comprehend, however the information is still accurate.
Furthermore, in the video during the explanation of how the amygdala shapes our emotions in fight or flight response and the connections of the amygdala, the information presented has neuroscientific correctness. The locations of anatomical structures are correct and so is the information on the amygdala connections but the connections are only briefly covered, and we are left without a more in-depth explanation, as there is no elaboration on aspects such as the inputs or outputs of the structures mentioned. This being said, the video should be commended for its scientific accuracies and ability to convey its information appropriately to its intended audience.
How we come to choosing this topic is not merely by chance. Almost all of our group members had completed the course Anatomy or Neuroanatomy in their previous semesters and are familiar with the limbic system – particularly the structures and functions of amygdala and hippocampus.
Firstly, we agreed on the search for an online media item about hippocampus and its relation to memory loss such as anterograde or retrograde amnesia. However, the search proved futile results since the media items did not introduce any new discoveries or concepts and resembled a text book material as it only contained fundamental information on the anatomical structures of hippocampus and brief explanations of amnesias.
Thus, we searched for related videos about amygdala on YouTube and one of our group members came across this ‘Amygdala Hijack’ clip and all of us immediately agreed upon choosing this as our media item. The concept of amygdala controlling the brain is novel to us and its association with the prefrontal cortex offers us the opportunity to research more on this area in the frames of neuroscience. The video itself was uploaded by an amateur but the scientific content of the clip comes from the well known clinical psychologists and neuroscientists that made us consider this media item a good choice.
Bruno, H.E. (2011). The Neurobiology of Emotional Intelligence -Using Our Brain to Stay Cool under Pressure.
Hadley, J. (2010, May 9). Emotional Intelligence.
Holistic Healing Newsletter
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LeDoux, J. (2007). The Amygdala.
Current Biology ,17
(20), R868- R874.
Nolte J. (2009). The Human Brain an Introduction to Functional Anatomy. 6th ed. 596-627.
Peters, K. (2011). Neuroscience, Learning and Change.
The Ashridge Journal.
, learning and change/$file/NeuroscienceLearningAndChange.pdf
Waxman, S.G. (2010). "Chapter 19. The Limbic System". Waxman SG: Clinical Neuroanatomy, 26th ed. Retrieved from
YouTube (Producer). (2010, March 18).
Emotional Intelligence or Behavourial Control? Part 1.
[Video Podcast]. Retrieved from
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