Comment by cess11

What you experience as perception happens inside the brain, it's inherently deceptive. With suggestive practice you can teach your brain to 'perceive' all sorts of things that to you appear as real as any other perception.

One way to study this is to shut off the neural channels for external stimuli with NMDA-antagonists or isolating the entire body, you'll experience immersive perceptions, including visions. Falling for various degrees of decoration your brain provides spontaneously or has been trained to provide is foundational to many religious and mystical currents throughout history. Some of them consider not falling for at least some of these things to be the basic exercise of their regimes, e.g. non-reaction to mental phenomena in Goenka's vipassana or time-locked prayer as in canonical hours and islamic prayer.