The mind-brain exhibits self-organized criticality. For good or ill, early activity patterns become embedded.
With somewhat malleable compensation for physical damage owing to limited redundancy, the brain has a certain robustness. People who exercise their mind-brain by learning and problem-solving throughout life may have their brains ravaged by Alzheimer’s disease, yet retain a goodly portion of their memories and mental facilities.
Conversely, the brain is fragile. By altering epigenetic dynamics which never revert to healthier functioning, early traumas can have lifelong effect. For example, altered amygdala activity in early life may result in pathological aggression in adulthood.