The pattern of blood flow in the prefrontal cortex in the brains alters with age during multi-tasking, finds a new study. Increased blood volume, measured using oxygenated haemoglobin (Oxy-Hb) increased at the start of multitasking in all age groups. But to perform the same tasks, healthy older people had a higher and more sustained increase in Oxy-Hb than younger people.