I found out today that there are already "brains in a vat", so called brain organoids, made from human pluripotent stem cells, and apparently, if you introduce a neanderthal gene into them, it affects their development. That (along with other research done on them) would seem to imply at least some resemblance in organizational structure with functional brains.
To properly consider the ethical and philosophical implications I feel will take time, but today I've definitely updated my model of the present.