Yeah, find these highly dubious. A heart transplant is quite a traumatic event, both physically and emotionally, who knows what side effects the patients were experiencing after the procedure.

Yes but the heart contains a lot of neurons so it's an interesting theory.

Over half of all neurotransmitters, including 80-95% of seratonin, originates in the gut. I wouldn't be surprised to hear a microbiome-based theory of personality but cellular memory is a new one to me

Possibly related: it turns out horizontal gene transfer is way more common in humans than we could expect and we really don't have a good explanation for how it's happening

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5379729/

Over half of all neurotransmitters originates in the gut, but the barrier preventing the entry of neurotransmitters into the brain is very effective in healthy individuals.

Signals from the gut to the brain arrive via the vagus nerve and probably also the other cranial nerves.

Interesting! The way I've often heard it is that "over half of neurotransmitters originate in the gut" — making it sound like it's talking about the neurotransmitters already at the brain. Do you have any citations that could clarify this?

Neurotransmitters are used all over the body. A lot is centralized in the brain, but the periphery also uses neurons and neurotransmitters.

Neurotransmitters in general don't particularly imply they're being used in the brain. Some neurotransmitters travel through the body, but a larger fraction are produced locally by a cell and intended only for close neighbors.

I probably learned that fact from an episode of neuroscientist Andrew Huberman's podcast--more likely than not episode one:

https://youtu.be/H-XfCl-HpRM

that concept is part of the premise of Parasite Eve, a great novel, turned into a shitty movie, turned into an alright game.

Same as "The Marked heart" / "Palpito" / "Herzschlag" on Netflix.

(For those about to watch it: the soul-vibing Neighbours-esque intro song is all part of the charm of this show. The shittier the intro, the more dramatic the needless melodrama is in contrast)