One must be careful not to confuse the primary images, or archetypes, as existing on another plane in the same way as Plato’s Forms. They are not otherworldly, but part of our animaterial universe. They abide in our bodies and in our souls, these being one and the same. Biology and psychology should not be separate disciplines. The universe in itself is not dualistic.
Does the imagination lie in the brain? It doesn’t matter. We are composed of animaterial particles through and through, as is the entire universe. All is soul. The imagination is an emissary of images. Images are received via the imagination and flow to our conscious minds. They originate in unconscious depths and rise to our awareness through the emissary. Unconscious depth is not otherworldly, but part of the animaterial universe.