Those who have never endured the relentless ringing of tinnitus can only dream of the torment. In fact, a bad dream may be the closest some get to experiencing anything like it. The subjective sound, which can also be a hissing, buzzing, or clicking, is heard by no one else, and it may be present constantly, or may come and go. Neuroscientists at the University of Oxford now suspect that sleep and tinnitus are closely intertwined in the brain. Their findings hint at a fundamental relationship between the two conditions – one that has, surprisingly, been overlooked in the brain until very recently. “What first made me and my colleagues…