MODEL RELEASED. Sleep apnoea research. Young woman attached to electrodes to measure her brain, heart and face and neck muscle activity as she sleeps. The brain activity is shown as an EEG (electroencephalogram) trace and the heart activity is shown as an ECG (electrocardiogram) on the monitor at left. Sleep apnoea is a disorder in which breathing is interrupted during sleep. Breathing usually resumes within a couple of seconds, although it may take as long as a minute. Overweight men are most at risk of sleep apnoea, although it can affect anyone. Treatment is with a controlled stream of air pumped through a face mask. Photographed at the Sleep Research Unit, American Hospital of Paris, France.