What happens in, for example, a LSD-trip - which many people see as a gateway to spiritual dimensions - is, that the consciousness draws more and more energy, and more content, in from the collective images.
The danger is that the past, or future, can suck life out of the present. The memories can in higher and higher degree be transformed into reality, while reality becomes emptiness.
The same can happen in the so-called Kundalini Yoga, and through Pranayama breathing exercises.
Meditation is, as I understand it, with reference to art of life, the opposite movement.
And by the way I believe, that this is a fact concerning all spiritual practice, when practised correctly.