(This question is in relation to this question here)
How does fear paralysis occur? What is the mechanism that makes this happen in brain?
The Fear Paralysis Reflex begins to function very early after conception and should normally be integrated before birth. It can be seen in the womb as movement of the head, neck and body in response to threat.
It is sometimes classified as a withdrawal reflex rather than a primitive reflex. If this reflex is retained after birth, it can be characterised by withdrawal, reticence at being involved in anything new, fear of different circumstances, and is often described as the “scaredy cat” child who bears the brunt of teasing by normally adventurous children.
This behaviour appears to be due to the reflex’s involvement with the parasympathetic nervous system. Most of us are familiar with the “fight or flight” adrenalin rush of the sympathetic nervous system, however the FPR taps into the opposing system urging the body to “eat and stay”. The parasympathetic nervous system is intimately involved with the vagus nerve. This nerve comes directly from the brain to aid the organs. It bypasses the spinal cord, so in the case of spinal injury we are still able to digest our food. The vagus nerve may be mechanically trapped in the skull, chest, abdomen or neck. Release of this nerve entrapment corrects one physical factor that contributes to the retention of the FPR.