Then why isit possible for the biochemistry to change the gati?
There is a famous example of a huge personality change of Gage after an accident of a rod passing through his skull:
“Popular reports of Gage often depict him as a hardworking, pleasant man before the accident. Post-accident, these reports describe him as a changed man, suggesting that the injury had transformed him into a surly, aggressive heavy drinker who was unable to hold down a job.”
”In a 1994 study, researchers utilized neuroimaging techniques to reconstruct Phineas Gage’s skull and determine the exact placement of the injury. Their findings indicate that he suffered injuries to both the left and right prefrontal cortices, which would result in problems with emotional processing and rational decision-making.9”
Would you say that it is a kamma vipaka to change his gati? If an arahant is subject to the same accident, would he have a similar result?