Think of consciousness as a stream. Water can flow along the stream through its entire length; that is, water is not localized in the stream, but traverses it unlimited. Now imagine a small whirlpool in the stream: It has a visible and identifiable existence; one can locate a whirlpool and delineate its boundaries precisely; one can point at it and say "here is a whirlpool!" There seems to be no question about how palpable and concrete the whirlpool seems to be. Moreover, the whirlpool somewhat limits and localizes the flow of water: The water molecules trapped in it can no longer traverse the course of the entire stream unbound, but become locked, swirling around a specific and well-defined location.
Now, there is nothing to the whirlpool but water itself. The whirlpool is just a specific pattern of water movement that reflects a partial localization of that water within the stream. When I talk of the brain being a structure in consciousness that reflects the self-limitation of consciousness, I mean something very analogous to the whirlpool in a water stream. There is nothing to the brain but consciousness, yet it is a concrete, palpable reflection of the localization of that consciousness. You can point at it and say "here is a brain!"