Can you tell me how are spiritual visions explained by science?

Neuroscience: attmpts to measure such things by brain activity. The do not comment on the subjective value or validity of visions. Theologians often ask the person to consult with a learned person to look at the impact of visions and other phenomena to see their positive or negative value. Beyond that, faith is the issue and a personal matter. Peace and good health.

Visions are the: brain giving you the illusion of experiencing external stimuli. Even in everyday life, your eye doesn't see anything, really. It just converts light into signals that stimulate your brain. Your brain reacts in a way that you perceive as sight. Under some conditions, your brain can misinterpret eye signals or even act on its own in a way that causes you to "see" something not there.