More importantly, when a mouse looks at a gray screen between images, neurons sometimes fire in a similar, but not identical, pattern as when a mouse looks at an image, indicating That he was daydreaming about the image. These daydreams occurred only when the rats were rested, and were characterized by calm behavior and small pupils.
Not surprisingly, the rats daydreamed more about the most recent image and had more daydreams at the beginning of the day than at the end, when they had already seen each image dozens of times.
Throughout the day and throughout the day, the activity patterns changed as the rats viewed the images – what neuroscientists call “representational drift.” Yet this flow was not random. Over time, the patterns associated with the images became even more distinct from each other, until each involved an almost completely different set of neurons.
Specifically, the patterns seen during a mouse’s first few daydreams about an image predicted what the patterns would be when the mouse later viewed the image. “There are changes in how the brain responds to the same image over time, and these early daydreams can predict where the drift is going,” Anderman said.