It’s a fascinating article, but I kept looking for links to the scientific studies mentioned. I came across this by googling:

[nature.com]

[heartmath.org]

There are a lot of claims online about this subject, with statements like “research shows”, but no links to any real studies.

It makes sense that an organism’s entire nervous system be considered a unified whole. It’s all connected.

No. Wishful thinking by grieving relatives. There are some remaining brain cells in our spinal cord, but they are in the higher sections.
More science is needed. Under a heart transplant the patient is under a coma and some brain damage occurs.. and for some people a lifesaving procedure is a personality change in itself. I was in a coma for four days. I have memory loss from it. What were we talking about? Who's chair am I sitting in?

See no reason why not. The idea has millenia of thinkers considering it.