A mouse study published in Nature has taken a team led by Harvard Medical School researchers one step closer to understanding what happens in the brain during daydreaming. The researchers monitored the activity of neurons in the visual cortex of mouse brains while the animals were awake and silent. They discovered that these neurons occasionally activated in a fashion similar to that seen when a mouse gazed at a real image, suggesting that the mouse was thinking--or daydreaming--about the image.