Brain
The grey organ in the skull — the seat of all the thinking the rest of the body relies on.
A brain in a dream is the dream's image of the seat of all the thinking the rest of the body relies on. The brain is rarely seen in waking life; the dream uses it when the question of thinking itself is in view. The dream brings the brain when something in your life — a decision process, a learning capacity, an act of judgement — is being looked at as the central machinery rather than as its outputs. A brain intact and active is the dream affirming the function. A brain bruised, damaged, or out of its case is the dream noting that the central machinery itself has been injured, and the outputs that depend on it cannot be trusted until it heals.