What is misunderstood about perception is that our brain in fact doesn't do anything but perception. Neurons are connected to our environment, but also to themselves. Neurons as a whole system can work together to perceive that which is imperceptible by the separate functions of the brain. Our eyes are part of our brain, and we can perceive much more than just the visual spectrum of light with them.
Discussion
Yes. I feel that over the course of one's life, certain filters develop that limit one's perception, so the brain has to process less. LSD dissolves these filters, expanding perception, which can overwhelm many at first.