Take a break and let your mind wander... Maybe daydream about future plans, or muse on past times. Although you won't notice, you're switching on certain parts of your brain called the default mode network, which kicks in when we daydream. Scientists think that a chemical signal called serotonin, which enables nerve cells to 'talk' to each other, is somehow involved in switching between daydreams and focusing on tasks in the real world – something that can be a problem in people with depression. This image represents a scan of a healthy volunteer's brain, revealing areas that are more (pale/dark blue) or less (red/yellow) active depending on how quickly serotonin is mopped up by cells in the blood around the brain. The yellow bits are all part of this daydream network, confirming that serotonin is likely to be involved and opening up new avenues for understanding how our brains work.
Written by Kat Arney
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.