>how do we understand the connections between various regions.<
On bigger levels that might depend on the regions (like where understanding
some and where not at all) and might be more regarded as a sort of shunt way
between them.
Apart from that different individuals might understand such differingly.
... And if one never understands all about brains that leaves aspects to wonder
about and protecs humans from those wishing to rule others in the future having
it easier to try to force in data sniffing and controls.
It protects personal privacy better, the less they understand there, the better
it might be regarded.