I am not sure about an Old Brain theme, will have to circle back after more thought or reading other's examples.
I was intrigued by the mind-body connection when I started to develop a list of chronic physical issues from 2011-2014.  Conflicts were overworking/doing too much regarding work, bad relationship and ending it in 2011 and also connected to that family member betrayal/judgment and then relationship change (loss) which is still ongoing and with having done a lot of work am getting ready to directly address the 'elephant in the room' with her.
New Brain:  self-devaluation; perfectionism, not good enough/not doing enough, fear of judgment
Chronic tension in *neck, shoulders, jaw, back, hips...since late 2011/2012. Tension and vascular headaches, chronic tension felt to some degree in the head since 2013.  Overall intensity and/or duration of tension has reduced with self-regulation/resourcing.  When a flare up occurs or tension intense it does serve to slow me down and take a break.
I also have tinnitus which I believe connects to hearing something I didn't want to and not wanting to hear again.
Seem to spend time in sympathetic flight mode (doing too much or thinking I have to, overthinking, to help prevent possible judgment and not good enough and also to distract from), some time in pleasing mode (fawning) which could be sympathetic and/or parasympathetic?