CONTRARY to popular belief, a rush of blood to a certain brain region is not always linked to neural activity there, a finding that may guide future brain scan experiments.

Functional MRI scans measure blood flow in the brain. Neuroscientists interpret this as a sign that neurons are firing, usually as someone performs a task or experiences an emotion. This enables them to link the emotion to the brain region where there was blood flow.

Now, Aniruddha Das from Columbia University in New York and colleagues have shown that blood flow can occur without accompanying neural activity. Das used …