What, exactly, is the notion of cause and effect at work in a causal series that includes the citta-santāna?

What, exactly, is the notion of cause and effect at work in a causal series that includes the citta-santāna? I suppose the obvious answer is the 12 links of dependent origination, but I am confused ***how*** ignorance causes sankhara to arise. **Obviously, speculating where will be reborn is frowned upon, even if suggesting that rebirth may work even with some views (such as mind-brain identity) is not.** ---------- Suppose that it reduces to something physical, so that my *brain state* for my "death thought" must bring about a new brain state somewhere: is it very conceivable, in contemporary physics or biology, that the state of my brain right sufficiently for citta-santana with an existing (or just coming into existence) brain state that is not "my" brain?