The conundrum of mind and matter: what is consciousness?

It’s one of the greatest puzzles scientists struggle to define. Susan Greenfield explains why understanding consciouness remains elusive
It’s early in the morning and still dark outside. Your heart rate has dropped to a single beat per second and your blood pressure is the lowest it will be for the next 16 hours. Your respiration has fallen to 12 breaths a minute, while your blood glucose is at rock bottom. Despite the ingenious physiology remorselessly at work in all your organs, yo