Consciousness remains a central mystery in science, with debates over how the brain generates subjective experience, personal identity, free will, and whether consciousness itself is an illusion. Advances in brain science involve biologists, neuroscientists, psychologists, and philosophers. This work clarifies major theories and arguments, covering the construction of self in the brain, mechanisms of attention, neural correlates of consciousness, and the physiology of altered states. It highlights the rapid pace of neuroscience discoveries.
Altered states of consciousness (ASCs) include sleep, dreaming, hallucinations, out-of-body experiences, near-death experiences, meditation, and states induced by psychoactive drugs. Psychologist Charles Tart defines an ASC as a qualitative alteration in the overall pattern of mental functioning that feels radically different from ordinary consciousness, though this definition raises questions about what constitutes a 'normal' state. In mystical experiences and long-term meditation, people report seeing through the illusions of duality and perceiving the world as it truly is.