How do our personalities and mental processes, our "states of consciousness," derive from a gray mass of tissue with the consistency of a soft-boiled egg? How can mere molecules constitute an idea or emotion?

Some of the most important questions we can ask are about our own consciousness. Our personalities, our individuality, indeed our whole reason for living, lie in the brain and in the elusive phenomenon of consciousness it generates. Thinkers in many disciplines have long struggled with such questions, often in ways that have seemed incompatible, if not downright contradictory.

Philosophers have meditated on the subjective experience of consciousness, with little attention to the physical realm, while scientists have sought to establish a causal relation between brain function and mind, often ignoring the qualitative aspects of experience.

In Journey to the Centers of the Mind, neuroscientist Susan Greenfield offers an intriguing, unifying theory of consciousness that encompasses both phenomenological mental events and physical aspects of brain function. Using information gathered from clues in animal behavior, human brain damage, computer science, neurobiology, and philosophy, Greenfield offers a "concentric theory" of consciousness, and shows how certain events in the brain correspond to our qualitative experience of the world.

Demonstrating the ways in which we can interpret the experience of consciousness in terms of interactions among neurons, she explores how much we can learn by continuing to find the links between our physical and mental inner worlds.