The Role of the Amygdala in Fear and Panic

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Biology 202
1998 Second Web Reports
On Serendip

The Role of the Amygdala in Fear and Panic

Doug Holt

The definition of fear has proved to be an elusive mystery plaguing scientists. While there is much agreement as to the physiological effects of fear, the neural pathways and connections that bring upon these effects are not well understood. From the evolutionary standpoint, the theory is that fear is a neural circuit that has been designed to keep the organism alive in dangerous situations (1). How does it all work? Learning and responding to stimuli that warn of danger involves neural pathways that send information about the outside world to the amygdala, which in turn, determines the significance of the stimulus and triggers emotional responses like freezing or fleeing as well as changes in the inner workings of the body's organs and glands (1). There are important distinctions to make between emotions and feelings. Feelings are "red herrings", products of the conscious mind, labels given to unconscious emotions (2) whereas emotions are distinct patterns of behaviors of neurons. Emotions can exist of conscious experiencesas well as physiological and neurological reactions and voluntary and involuntary behaviors (3). But the components of fear goes beyond feelings and emotions. It is also the specific memory of the emotion. After a frightful experience, one can remember the logical reasons for the experience (e.g. the time and place) but one will also "feel" the memory, and his body will react as such (i.e. increased heart and respiration rate, sweating). In one recent case, after a near drowining incident, the victim could not only vividly remember each detail, but when doing so, his body reacted as though he were reliving the experience. These feelings of memory are stored in an almond shaped structure in the brain known as the amygdala.

The amygdala is the name of the collection of nuclei found in the anterior portions of the temporal lobes in the brains of primates (4). The amygdala receives projections from frontal cortex, association cortex, temporal lobe, olfactory system and other parts of the limbic system. In return, it sends its afferents to frontal and prefrontal cortex, orbitifrontal cortex, hypothalmus, hippocampus, as well as brain stem nuclei (20). After this point, neither the concrete definition as to the extent of the amygdala is not clear, nor is the exact function of each of its subgroups. In the amygdala region alone, there is much controversy surrounding the nuclear subgroups, resulting in classifications that range between 5 and 22 different groups within the amygdala itself. Despite all of this, there are four main groups that have been universally agreed upon. These are the Basolateral, Lateral, Central, and Basomedial nuclei. The amygdala is considered to be the key component to the limbic system, a term that has also been regarded with much recent controversy by researchers in the field of emotions. One of the biggest surprises from LeDoux's work is that there may be no such thing as the limbic system – a brain structure that has been supposed to underlie emotion and motivation. "All students are taught about the limbic system," LeDoux said, "but in my opinion, it's no longer a valid concept." (2) Reasons for his assertations center around the investigations of the mechanisms by which the amygdala processes information regarding threats and fear. The classic model of the limbic system encompasses the hippocampus, the amygdala, and a few other small structures. These structures supposedly receive sensory input from the outside world – sight, smell, hearing, touch, and taste, as well as from the viscera. When these sensations are integrated in the limbic system, emotional experiences are thought to occur (2). While the fear circuit does indeed appear to incorporate the amygdala, the hippocampus and the other limbic structures are not involved. They are bypassed in the fear circuit. But fear and its emotional memories are not the only things controlled by the amygdala. The amygdala has up to 22 distinct regions and only two so far have been clearly implicated in fear (2). The flight and fear responses may be obtained from the rostral regions of the amygdala, including the lateral nucleus, the periamygdaloid area, and the central nucleus. Defense or aggressive reactions could be obtained from the medial and caudal aspects of the amygdala (4). These reactions have been observed by the selective stimulation of amygdaloid nuclei in laboratory animals.

In a related process, another responsibility of the amygdala is the suppression of the periaqueductal gray. The periaqueductal gray is another major structure involved in the interpretation of fear. It is a large structure in the midbrain, consisting of small to medium neurons surrounding the aqueduct of Silvus, otherwise known as the cerebral aqueduct. The periaqueductal gray is thought to be involved in protection and defensive reactions (15), notably distress calls and affective defense. Affective defense is characterized, for example, in cats by unsheathing of claws, baring of teeth, hissing, piloerection, paw striking, and arching of the back (15). When selectively electrically stimulated, the amygdala suppresses these behaviors and causes freezing. Freezing is a robust index of learned fear (16).

What is known about the amygdala is that it has a dual sensory input system. Both inputs run from the eyes, ears, and other sense organs to the thalamus. At that point the inputs diverge. One pathway leads directly to the amygdala while the other first passes through the cortex. Each input causes a distinct and specialized behavior. The amygdala is specialized for reacting to stimuli and triggering a physiological response, a process that would be described as the "emotion" of fear (2). After this, the stimuli of the activation of the amygdala is transmitted to the cortex. This is a distinct difference from a conscious feeling of fear. Feelings are thought arise from the second, slower pathway that travels from the sensory input first to the higher cortex and then to the amygdala. In the cortex the frightening stimulus is analyzed in detail, using information from many parts of the brain, and a message is sent back down to the amygdala (2). While having both systems in place may appear to be redundant, its purpose is invaluable. The initial signal, activating the amygdala and its corresponding physiological behaviors, prepares the body for immediate reaction to the stimulus. This is part of the startle circuit. Its physiological effects are similar to the initial stages of fear. By having the body ready for action, the second circuit can then take a moment to analyze the signal in its entirety to determine whether or not the threat is real or perceived. If the threat is real, then the body is already on the go, if perceived, than nothing has been lost. But there are problems associated with the double wiring between the higher cortex and the amygdala. Unfortunately the neural connections from the cortex down to the amygdala are less well developed than are connections from the amygdala back up to the cortex. Thus, the amygdala exerts a greater influence on the cortex than vice versa. Once an emotion has been turned on, it is difficult for the cortex to turn it off (2).

Through the usage of fear conditioned rats in laboratory settings, researchers have been able to effectively map out the "fear circuit". The fear circuit is stimulated in rats by means of placing the animals in metal boxes and subjecting them to foot-shocks associated with an auditory signal. This method effectively conditions the rats to fear both the metal boxes in which they had experienced pain and the corresponding auditory signal. After experiencing these stimuli, the rats, when exposed to the auditory signal, react with fear. The same fear is expressed when placed inside of the conditioning box, whether or not foot-shocks were applied. Through these experiments, it has been determined that the amygdala is required for both the fear circuit and the memory of fear (conditioned fear) associated with stimuli. These determinations were made through selective lesions of the auditory pathway through to the amygdala. Only when selective lesions were made on the amygdala, did the laboratory animals not respond to the frightening stimuli.

Occasionally, there can be debilitating problems associated with hyperactivity of the amygdala. Being the storehouse for the memory of fear, it can misinterpret signals from the body and cause inappropriate actions. This can lead to panic. Panic is a heightened stage of anxiety and fear feeding itself in a positive feedback loop and jumping to faulty conclusions, which focus on impending danger, madness, harm, or death. Physically, the body undergoes many changes that ready it for extreme action. There is a marked secretion of glucocorticoids and catecholamines which increases the blood glucose levels. Also, increase production of epinephrine and norepinephrine, which has the effect of vasodilation of blood vessels in skeletal muscles. Other symptoms of the sympatho-adrenergic stimulation involve modifications of breathing, increased temperature, localized sweating, decreased motility of the stomach, bowels, and intestines, constrictions of sphincters in the stomach and intestines, as well as piloerection (20). But the question of what generates panic attacks still remains essentially unanswered at the moment. There are many theories accorded to panic, the most prominent are:

Clark's theory on catastrophic interpretations (1988) sees panic attacks as a result of maladaptive and faulty interpretation of body signals. Beck's theory proposes a similar model, but based on predisposing and precipitating factors. Elhers' theory explains panic attacks as a result of panicogenic interoception. Barlow's theory proposes that panic attacks are modified "fight or flight" mechanisms in the absence of danger (20).

The limbic system, especially the amygdala, has long been considered to be directly implicated in anxiety and fear stages. The amygdala and its central nucleus thus communicate with many brain regions, including those that control breathing, motor function, autonomic response, release of hormones, as well as processing of interoceptive and external information (20). Therefore, the claim that the limbic system, with the amygdala and its central nucleus are implicated in panic attacks makes a biologically plausible hypothesis.

Fortunately, there are methods of reducing fear and inhibiting the fear response. Through testing with laboratory animals, it has been determined that when attention is shifted away from the anxiety-provoking stimulus, less fear is observed. When a novel stimulus is presented slightly before or at the same time as a well-trained condition stimulus, the condition response will be disrupted (18). This effect has been described using many methods but the neural mechanism is not well understood at this time. Another method of inhibiting the fear circuit is through conditioning. In a typical conditioned inhibition procedure, conditions are arranged such that one stimulus, denoted A, predicts shock, while another stimulus, denoted X, predicts absence of shock. The result of this procedure is that A comes to elicit a fear reaction when presented alone, but not when it is accompanied by X, the conditioned inhibitor (17). This is a similar method of treatment that is used for people with phobias. This method is inhibiting the emotional response produced by the amygdala during a threatening situation. The patient still remembers that he used to be afflicted by his phobia, but no longer has the emotional response attached to it (3).

There is much correlation between the emotional states of fear. Anxiety, distress, and fear are closely related negative emotional states associated with physical or psychological harm. These three emotions can be differentiated by the temporal relationship between the feeling and the potential threat. Anxiety is characterized by the anticipation of being harmed in the future, where as fear is characterized as the anticipation of being harmed in the present. Distress is characterized by the awareness of being harmed at this particular moment. The three emotions can diffuse into one single diffuse state (5).

 

Works Cited

1.) LeDoux "Emotion, Memory, and the Brain"

2.) LeDoux "Using Rats to Trace Routes of Fear"

3.) LeDoux "A Neural Model of Fear May Lead to a Better Understanding of Other Emotions"

4.) Isaacson, Robert. The Limbic System. Plenum Press, New York, NY, 1982

5.) Thompson, Jack George. The Psychobiology of Emotions. Plenum Press, New York, NY, 1988

6.) "The Main Areas Involved with Emotions"

7.) "Theories of the Role of Brain Structures in the Formation of Emotions"

8.) "Phobias: When Fear is a Disease"

9.) "Aversive Motivation"

10.) "How the Brain Feels Fear"

11.) "How the Brain Feels Fear"

12.) "Emotion: Circuit Level: The LeDoux Circuit"

13.) "Amygdala Home Page"

14.) "Research Reveals Clues to Who Suffers Panic Attacks"

15.) "The Anatomy of Fear"

16.) "Stephen Maren, Ph.D."

17.) Van Goozen, Stephanie H. M. (ed.). Emotions: Essays on Emotion Theory. Lawrence Erlbaum Associates, Publishers, Hillsdale, N.J., 1994

18.) Kavanaugh, Robert. Emotion: Interdisciplinary Perspectives. Lawrence Erlbaum Associates Publishers, Hillsdale, N.J., 1996

19.) Muller, Jeff, "Functional Inactivation of the Lateral and Basal Nuclei of the Amygdala by Muscimol Infusion Prevents Fear Conditioning to an Explicit Conditioned Stimulus and to Contextual Stimuli". Behavioral Neuroscience, Vol. 111, No. 4, pp. 683-691, 1997

20.) "Brain Structures Implicated in Panic Disorder"

"Gene That Influences Fearfulness in Mice Discovered"

"The Fear Trigger"

"Medial Temporal Lobe"

 

 

Comments made prior to 2007

This is a great summary of the origins and mechanisms of fear, anxiety and distress. These 3 harmful emotions cause amazing amounts of damage, as alluded to in the paper, and in my opinion can be linked to the harm done by bullies. In the growing concern for schoolyard, workplace, political and home based bullies and the affects on targets, it seems to me that solutions lie in the amygdala, as mentioned in the book, Emotional IQ. For the targets of bullying however, perhaps the solutions listed below, to interupt the pathway and make the stimuli less toxic, could contribute to helping targets and thus, ameliorate not only some of the physical effects, such as death, heart attack and stroke, but also cut down on the costs to society of bullies. Is evil then a dysfunction of the amygdala? Is this a center of narcissism? ... Diane White, 31 March 2006

Comments

Serendip Visitor Vicki's picture

Anxiety Jan 2014 Book Release on topic

A wonderful new book has been written to give all of us anxiety/panic sufferers a detailed look inside this ailment. Check it out- My age of Anxiety: Fear,Hope by Scott Stossel. I was reading his book tonight about the amygdala and I found my way to this page. Very interesting. We are not alone in this. Its time for us to step out of the shame and despair and rally around one another! Together we are stronger.

Steve 's picture

Personal Trauma/Fear

Is it possible to write to your P.O. box or address about my personal experience?

Eduardo's picture

how about babies that have

how about babies that have had their amygdalas removed? this happened to me as I was a baby, because stupid doctors back at the 80's in my countries thought (what an arrogance) that this part of the human body had no purpose and often gets infected... so they just mutilate millions of kids.

But I have fear.... maybe there are other consequences for the lives of these people and this deserves research??

Gina's picture

maybe you mean adenoids?

maybe you mean adenoids?

Serendip Visitor's picture

Joke?!

Is this a joke?! The article is about a part of the brain, not the "amygdala" in your throat... Trust me, no one removed the amygdala found in your brain!

Serendip Visitor's picture

On second thoughts...

On second thoughts...

Olubunmi Aribisala's picture

Amygdala

If you can, may you please give me a brief explanation on the role of the Amygdala in memory. Thank You.

EMJAY's picture

Anxiety

I am currently trying to overcome my Panic and anxiety and depression.....And I actually feel like i'm making some headway...I am begining by trying to separate my emotions from my anxiety...ie..trying to look at it from an outsiders perspective...i also write down all the epiphanys i have when i am feeling super anxious or when for a moment its gone...i also write notes to my un anxious self to read when i am super anxious...it seem to be helping me to separate the emotion from the anxiety...but if anyone really knows a better method i'm all ears...God Bless you all...

Lauren O'Keefe's picture

Anxiety

I suffer with anxiety, panic attacks and depression. I recently found the Linden method. It has cured thousands of people like us. Im going to try it a they guarantee a cure or your money back! Have a read, I definitely think its worth it. Hope you get well soon. Lauren x

my name is willy's picture

anxiety,panic attacks and sleeping disorders

it is not a really good feeling having this symtoms is like you are not living in this word feeling of going crazy
every time im getting a panic attack i judt think that im not really sick and nothing is going to happen to me
i star thinking about dome other thing i know is hard to get it off your mind but if you try really hard it will go away
trust me i garantee it will go away in about three(3) minutes. And when you are about to go to sleep and you think that you goin to die
just say i am not sick i dont have any problem with my health
and nothing is going to happen to me
there is no reason i should be sick

Hope you guy get better just be possitive
and you will be ok :) WILLY.

Serendip Visitor caroline rowlands's picture

Personal Evolvement

The methods you have described using to help you offset your response would be effective up to a point (as you explain is the case.
WHAT YOU CAN DO IS MAKE THE METHOD STRONGER.
Here`s how you do that: combine the merely psychological understanding/linear thinking (that you are producing to replace the response) with emotional responses with the thoughts. So,imagine (picture/visualise) the fear situation and imagine putting a frame around it. Then snap out of that and for a few seconds sing/laugh anything to cut the connection ... NOW visualise an experience that illicites a feeling/sense of pleasure/enjoyment and bask in that enjoying every detail for a few minutes, see the colours, feel the textures smell the smells ... take it all in ... and then quickly take snapshot picture of it in your minds eye ... and then witha smile of appreciation just quickly have it shrink to palm size. Snap the connection and sing/laugh for 30 secs.

Now I want you to quickly bring to mind the big picture you framed of the unpleasant experience. Ok now instantly snap on the bottom right corner the small picture you took of the good experience and as it snaps into the corner let it watch it instantly expand and take over the WHOLE frame ... big smile ... excellent.

Now repeat this process 3 times in quick succession *leaving just a minute or so between each one.

Then do it a few times each day for a while :)))

David's picture

emotional memory

A few years ago I had a near death experience and spent a night alone on a mountain. Eight months later I was asked to rehearse the event in the presence of a therapist using emotion freeing technique.

When rehearsing the event, I was rather taken by surprise by the gush of tears and relived trauma, although maybe I am moving into grief. Anyway, the strong emotions were there.

I am not entirely sure what the effect of the emotion freeing technique was (if any), but I did not and don't seem to have the same intensity of emotions afterward.

Anonymous's picture

Please help

I suffer from schizophrenia and cancer. Because of my chemiotherapy, Iam reclusive most of the time, and I deal a
lot with paranoia and overactive imagination. Please help.

Serendip Visitor's picture

i think you should eat some

i think you should eat some chicken and waffels it makes the buggie man go away but it also gives you diabetes so yeah :)

Dave's picture

help maybe

I too am quite, uh, "oversensitive". In some people our fears are close to the surface. But I am somehow convinced everyone has to face and overcome their deepest fears. It's hard to help over the internet. Hard in real life too. May you find peace and a way to a bright future. Bless you.

Jim Witte's picture

Anxiety Attaks and Asperger's

Annette,

Please take a look at the following link:

http://www.ageofautism.com/2008/05/john-robison-ca.html

It is about a 60-year old man with Asperger's (of which the social component is believed to be mediated in part by an overactive aymgdala - at least when it comes to social situations).

He was essentially "cured" - at least or about a month and a half, by non -invasive trans-cranial magnetic stimulation (rTMS). The research is going to at the Center for Non-Invasive Brain Stimulation, whose web site is at TMS Lab (http://www.tmslab.org/).

I don't know whether/how this treatment/would apply to other types of anxiety that are not "Asperger's" (I think almost *all* currently classified "psychiatric" disorders will eventually be seen as parts of *biological* problems with the brain - mitochondrial dysfunction, deficiencies in certain nutrient, enzyme levels, etc. "Children With Starving Brains" talks about this specifically in the context of "recovering" (or partially recovering at least) children with "autism" (neuro-metabolic mitochondrial dysfunction - is probably what it should really be called..)

One of the treatments used in autism treatment is Hyperbaric Oxygen Therapy. The apparent clinical leader in the field here is Dr. Paul Harch, who runs a HBOT facility in Louisiana. See www.hbot.com.

There is on an-going "Pilot Study" of using HBOT to treat both TBI (traumatic brain injury) *and* PTSD in Iraqi War vets. The study has *no* placebo group - it is based on previous evidence of success - of which there is a lot. PTSD may be related to general anxiety disorder, and thus may respond to the same treatment (HBOT appears to induce the brain to *repair itself* - stem cell mobilization increases, and numerous growth factors are also up-regulated by the treatment). They would be worth a call I think - they are quite friendly, especially Juliette who is a nurse there as well as Dr. Harch's wife.

Finally, one of *the* tell-tale "symptoms" of Asperger's/autism is eye-gaze aversion. This is thought to be mediated by an "over-active fear reaction" to direct eye gaze (what is the first rule when you run into a strange dog? Don't look it in the eye..) I suppose in "normal" people, this reaction is somehow suppressed by a a link to the later-developed (in evolutionary time) "human" neocortex.

The naturally produced neuro-hormone oxytocin appears to be implicated in this - this was actually shown by the research Gustella in 2002 in his article "Oxytocin increases gaze to the eye region of human faces." (see http://www.ncbi.nlm.nih.gov/pubmed/17888410)

I can confirm that oxytocin does appear to decrease eye-gaze aversion to some degree (although perhaps I was not using enough of it - like most hormones, the correct dose for a particular individual is "enough"..) One interesting thing it DID do was to reduce my need for an anti-anxiety drug (Ativan - dosage is stable and non-addictive in me) by HALF. My antidepressant dose also went down - by more than half.

I can be reached at jw5587@gmail.com (which is of course a semi-temporary spam-proof [maye..] email)

anxiety remedy's picture

anxiety remedy

To cure anxiety attacks, herbs are the best medicine. No side effects, no giddiness, etc. Deep breathing exercises are excellent for anxiety and many people report positive results from meditation. Some other natural anxiety remedies to look into are St.John's Wort, SAMe, L-Theanine, and Tryptophan.

Anonymous's picture

Amygdala Article

Thanks for all the info. I'm writing a paper on this for psych class. Very informative.

Mark's picture

Great article. I have never

Great article. I have never heard of the amygdala

vishal walia's picture

hi I SOMETIMES FEEL THAT I

hi
I SOMETIMES FEEL THAT I HAVE SOME FEAR IN MY MIND BEFORE DOING ANY ACTION AND IT TAKES A LOT OF TIME TO TAKE ANY ACTION. REST EVERY THING IS FINE.PLS ADVICE SHOULD I NEED TO GO UNDER ANY TREATMENT OR SOME MEDICINE WILL HELP.

Anonymous's picture

Fear and panic

Hi Vishal
Try and find out if you can access a Human Givens therapist. Using a system called the rewind technique, which is a safe and hugely effective method done in a relaxed state of hypnosis, you can overcome anxiety and the overactive amygdala in an hour. You can find out more about it on the Mindfields College website. I have recently trained in this technique and used it with great effect. I can assure you that it is a gentle technique and one that fully respects you and your circumstances. It's wonderful for PTSD and various phobias.
All the best.

Elisabeth's picture

Human Givens therapist

Hi,

I would like to work with a HG therapist. However, none are listed in the United States on the professional register list. Where are you located? Would you be willing to do a phone session if there is no practitioner near me?

Thanks,
Elisabeth Webber

super7's picture

What part of the brain controls fear?

I like the information you posted on this site. It was very interesting and helpful!

Anonymous Ann's picture

Amygdala and fear and anxiety

I'm currently researching the role of the amygdala and find this the most interesting paper. Does anyone know if the freezing of the amygdala can be unblocked, so that the individual can be free to live a normal life? My research is proving some amazing results through studying only two years of a Bachelor of Contempory Arts in Theatre. Ann Wilson 22/11/2008

Anonymous's picture

Extreme interest in the information on this page

Suffering from the above I'm interested in to what possible treatment,surgical, or other medical procedures or treatments are available to correct maladies as described above -- I have been house bound for 3 years and got a computer so that I can research what is wrong with me -- tonight I truly believe that after reading this is hits the nail on the head and directly applies to my situation -- can some one please respond and give me some type of guidance or instruction as to what I can do to address my problems if in fact they are related to what your website is describing -- I'm anxious and hopeful that someone will reach out and provide me with any type of contact to pursue helping myself -- I am tired of sitting at home and tired of anxiety attacks, and want to not dread going to sleep knowing I'll just have another horrific nightmare that wakes me up in the middle of the night with a POUNDING racing heart thinking that this will be the night I am most certainly going to have a heart attack -- clearly I am in trouble and need help -- Thank you for any thing you can share with me that I can pursue -- Annette

Serendip Visitor's picture

Linden Method

Annette, I have been house bound for 7 years. Take it from me, I agree the linden method is a joke.The program Lucinda Bassett has Attacking Anxiety and depression is also a joke. On hers, you just sit and listen to them have group sessions... Thats it big joke. Good luck to you.

Anonymous's picture

annette do yourself a huge

annette

do yourself a huge favor...get "the linden method" it will change your life.

he explains that is your amygdala. you have to relearn to be a non anxious person
also once you understand the method, research on the net is your worst enemy.. you are perpetuating and feeding your anxiety. there is nothing wrong with you. no one can help you.....except you. you give the anxiety its power and you can take it away. I used to have anxiety and then I got busy with a new girl and a new job and I literally forgot to have anxiety. have you ever "forgot" your anxiety for a moment and didn't have it? then when you thought about it, it came back. right? you can fix yourself. the net is just feeding your panic. Reset your amygdala by distraction. GET THE LINDEN METHOD!!!!

Anonymous's picture

That program(Linden

That program(Linden Method)is a joke. Don't waste your money.

Mark's picture

Linden program

Why do you say it is a joke. I am currently researching panic disorder and am very interested in what others think

kathy's picture

anxiety attacks

Annette - please consider Neurofeedback. There is a great deal of info on the web about it, and the successes with it. You will find alot of info about ADHD, but will also find info about depression, anxiety, fear, etc. Just google "neurofeedback". Unfortunately, health insurance doesn't usually pay for this treatment, but, check it out. It may be worth the $$ to give you your life back.
Here are some websites that may be helpful: www.flexiblebrain.com ... www.eegspectrum.com ... www.isnr.org ... www.eegspectrum.com/Applications/Anxiety
... http://www.neurodevelopmentcenter.com/index.php?id=31 I hope this helps!

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