Even if we knew everything about brains, right now we lack conceptual/philosophical insight to turn that data into something useful. In turn, neuroscience is not even primarily concerned with getting such data, it develops its own generalizations that paint a picture of roughly how brains work, but this picture probably won't be detailed enough to capture the complexity of human (extrapolated) value, even if we knew how to interpret it, which we don't.

I was also wondering about neuroscience. If we take a CEV approach, wouldn't neuroscience be useful for actually determining the volitions to be extrapolated?