A new device that monitors the waste-removal system of the brain may help to prevent Alzheimer’s and other neurological diseases, according to a study published today in Nature Biomedical Engineering.

In the study, participants were asleep when they wore the device: a head cap embedded with electrodes that measures shifts in fluid within brain tissue, the neural activity from sleep to wakefulness and changes in the brain’s blood vessels.

By measuring these three features, the researchers found they could monitor the brain’s glymphatic system, which acts as a waste-removal and nutrient-delivery system.