The radio-receiver metaphor doesn't go far enough as it still assumes a somewhat physical brain, but it helps at first untangeling yourself from materialism. If reality is nothing but a dream it would be no problem to dream up a brain that modulates the dream-content if it is manipulated.

- Taking red paint and spraying it over your wall will modulate the dream in such that the wall appears red.

- Taking a hammer and hitting your head will modulate the dream in more unpredicatable ways.

What if these processes are the same? It's nothing but stuff made out of consciousness affecting consciousness.