The amygdala’s main function is processing stimuli and the emotional and behavioral reactions to them. When stimulated, the amygdala causes aggression, fear, anxiety, and other intense emotions. The amygdala is most commonly known for processing threatening stimuli and producing the responses of fear and anxiety. Each of these two are processed in different places in the amygdala. Fear is the physical response to danger (stopping of digestion, increased heart rate, etc.), while anxiety is the psychological response to perceived danger. The main difference lies in the nature of the stimulus. The response of fear is linked directly to a specific stimulus, say, hearing a loud explosion nearby. Anxiety is not necessary linked to a direct stimulus, but results from a feeling of danger. For example, while someone is driving through a four way intersection, someone on the left runs the red light and crashes into the driver. Seeing the car just before crashing into the driver would evoke fear. For some time after that crash, the driver is anxious when getting on the road and worries that someone else may crash into him.
The above discusses fear and anxiety’s with respect to survival, but what about phobias and anxiety disorders? Well, it is thought that emotional memories are stored in part of the amygdala. This may play a role in how the brain processes these memories and how it chooses to respond to similar or apparently similar situations. Children who grow up being yelled at may feel threatened later on when another person yells at them. An example like this reflects how those childhood memories, being stored in the emotional processing center of the brain (which focuses on fear and anxiety), could be used to produce reactions in the person when placed in a similar situation years later.