Book excerpt: What is happening in the brain when we drink too much alcohol, get high on ecstasy or experience road rage? Emotion, says internationally acclaimed neuroscientist Susan Greenfield, is the building block of consciousness. As our minds develop we create a personalized inner world based on our experiences. But during periods of intense emotion, such as anger, fear or euphoria, we can literally lose our mind, returning to the mental state we experienced as infants. Challenging many preconceived notions, Susan Greenfield's groundbreaking book seeks to answer one of science's most enduring mysteries: how our unique sense of self is created.