In vivo imaging scientists broadcast from inside the brains of moving animals.
A message on an Alzheimer’s disease online board seeks advice about a 75-year-old aunt who incessantly yells at her 80-year-old husband without whom she cannot move about. The aunt has stopped eating and refuses a doctor’s visit. Behavioral changes in patients with Alzheimer’s disease—memory loss, impeded speech or motor skills, irritability, and other personality changes—leave loved ones clamoring for ways to lessen suffering. For now, medications can only slow the disease progression in some cases, not cure it. Neuroscientists are convinced that patients will benefit from new ways of peering into the brain that underlie behavior and the disturbance that brain diseases create.
To directly monitor the activity of neurons in the brains of awake, active animals as they move, react and remember, scientists have to create special experimental environments in which they can apply an evolving array of activity indicators: for example, calcium, whose concentration rises when neurons fire (Box 1). The animals may be moving or be partially restrained, and the imaging systems, based on modalities such as one- and two-photon microscopy1, are tailored to the animal in a variety of ways.