I’ve seen people’s entire personalities changed or wiped out by drug interaction or head injury. The core is physical, I’m sorry, but it just is. Most of what you attribute to “soul” is really just personality.
In saying “I’ve seen” you again unwittingly refer to a self, a “chooser,” a “chooser” who chooses to believe that all that exists is “matter” even though matter cannot account for personality...a metaphysical concept— anymore than it can account for soul, spirit, mind, and free will.
Materialism is not new, nor is it empirical science. Going back to the time of the ancient Church Fathers, materialists were then as now, denying their souls and comparing themselves to beasts while the Stoics (vitalists) scoffed at them, just as their modern “New Age” counterparts are doing.
The brain is the computer used by the soul. When the computer malfunctions or is infected by a virus, its’ user cannot communicate.