> How does one verify that their sensations during meditation are real reflections of how the brain works and not just subtle hallucinations?

I guess the scientific method[0] should be the de-facto approach.

But one shouldn't necessarily expect to reach certainty: science is intrinsically humble, as it merely limits itself to the creation of models of reality, and to their refinement, by way of minimizing the error between theory & experimentation.

[0]: https://en.wikipedia.org/wiki/Scientific_method