The amygdala area of the brain is designed to detect danger. It evaluates and processes information long before the information is going to be consciously processed. When the amygdala matches the environment, we have mental health. When it does not, that is when we begin to see mental illness.

If the amygdala perceives some sort of threat or danger, it activates in proportion to the perceived threat. If it perceives the threat as little, it will activate a little, if it perceives the threat as major, its going to activate a lot.

When the amygdala activates, one thing that it does, is it sends strong signals to the upper areas of the brain, to actually shut them down.

Sometimes, the amygdala hijacks the brain.

Therapists and clinicians will therefore often need to deactivate the amygdala in order to engage in therapeutic processes (cognitive processes in particular require prefrontal cortex access) requiring access to the upper brain.