shame
/SHām/
noun
a painful feeling of humiliation or distress caused by the consciousness of wrong or foolish behavior.
We've all heard the phrase "shame on you" - it conjures up memories of childhood - doing something that I knew wasn't right (and doing it anyway) and hearing the all familiar words "shame on you!" It didn't strike me at the time (or maybe it did) that the word "shame" carries a heavy meaning to us and our brains.
Brene Brown defines shame as the intensely painful feeling or experience of believing that we are flawed and therefore unworthy of love and belonging—something we’ve experienced, done, or failed to do makes us unworthy of connection.
The words "shame on you!" begin to make us aware of the feelings that because of something I did, I was unworthy of love, connection, and belonging. As adults, we oftentimes have an internal monologue of shame that we're not even aware of: shame on me for: not getting my work done on time, feeling burnt out, anxious, depressed; for not wanting to play with my kids; for letting my spouse down (again)...the list goes on and on.
When we think we have damaged our repuation, shame is triggered.
During fMRI studies, German scientists from Ludwig-Maximilians-University in Munich found that shame set off high activity in the right part of the brain but not in the amygdala. In the guilt state, there was activity in the amygdala and frontal lobes but less neural activity in both brain hemispheres. The researchers concluded that shame, with its broad cultural and social factors, is a more complex emotion; guilt, on the other hand, is linked only to a person’s learned social standards. (Glicksman)
Curt Thomspon writes in The Soul of Shame:
“When we experience shame, we tend to turn away from others because the prospect of being seen or known by another carries the anticipation of shame being intensified or reactivated. However, the very act of turning away, while temporarily protecting and relieving us from our feeling (and the gaze of the ‘other’), ironically simultaneously reinforces the very shame we are attempting to avoid. Notably, we do not necessarily realize this to be happening-we’re just trying to survive the moment. But indeed this dance between hiding and feeling shame itself becomes a tightening of the noose. We feel shame, and then feel shame for feeling shame. It begets itself.” (31)
"When faced with shame, the brain reacts as if it were facing physical danger, and activates the sympathetic nervous system generating the flight/fight/freeze response. The flight response triggers the feeling of needing to disappear, and children who have this response will try to become invisible. They will literally look smaller and their expressions become blank." (Davis)
Lucky for us, neuralplasticity allows us to rewire our brains. Neurons that fire together, wire together... as do neurons that fire apart, wire apart. Thus, we can slowly begin to treat ourselves differenly: through self acceptance, forgiveness, or just being less critical of ourselves. As Brene Brown simply and bluntly states: Want to be happy? Stop trying to be perfect.

Thanks to the following authors and for further reading:
BrainFacts
PTSD foundation