That Thing Called Fear

Suppose you got up this morning and left the house to go on your routine jog.  Suddenly, you see the next door neighbor's dog.  It barks softly at first, then progressively gets louder and more threatening.  Without any sign, it starts running towards you, growling and ready to bite.  You think to yourself, Should I outrun it?  Can I actually get away?  Or should I just head back into the house?  Who knows how well that dog can keep up with me.  Perhaps I can fling a stick in a random direction and it'll leave me alone.  The dog is now 12 feet away from you.  What do you do?  You realize you have a stick in your hand; you drop it and run.

This is the infamous fight-or-flight response that takes a hold of you when you fear something.  This article explains what happens during this process.  Unfortunately, there are several parts in the brain that are involved in fear, but the important parts include the thalamus, the sensory cortex, the hippocampus, the amygdala, and the hypothalamus.  I never again want to do a Google image search for "parts of the brain fear response" no thanks to my fear of spiders.  I have never hit the back button so fast in my entire life.  Nevertheless, here is a picture of the parts of the brain involved in fear.


The thalamus is responsible for sending data that was received from sensory locations, such as the mouth or the ears.  The sensory cortex analyzes the sensory information.  The hippocampus is a storage and reception area for conscious memories.  The amygdala interprets emotions, and the hypothalamus initiates the "fight or flight" response.   There are two methods in which fear is created.
The first way involves "tak[ing] no chances."  In the situation with the threatening dog, you have to assume that the dog is coming after you.  So, you should probably run back inside.  This process would entail seeing the dog (a stimulus) which sends information to the thalamus.  Next, the amygdala would interpret the fear sensed upon seeing the dog, Lastly, the hypothalamus tells you to run or fight the dog.  

The second way is a bit longer, but takes into account all the possible options.  First, there is the stimulus of fear, the dog.  You see the crazed dog and hear growling and barking.  Next, the thalamus receives this information, which is then sent to the sensory cortex for decoding.  The sensory cortex acknowledges that there are many interpretations of the data, and sends it to the hippocampus.  The hippocampus will access the memory bank to determine if this dog looks familiar, or if the dog is possibly running towards someone else.  The hippocampus will decide that the dog is after you because you have a stick in your hand.  It sends a "no imminent danger" message to the amygdala, which then tells the hypothalamus to shut down the "fight or flight" response. 

These two ways are only a short description of how the "fight or flight" response works.  Here's the extremely long way involving more minor parts of the brain.  So, the next time you feel that response kick in, you'll understand how it works.  I sure do after seeing spiders come up on that Google search.

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