Apparatus is provided for modifying a property of a brain of a subject, including at least one electrode, configured to be positioned in a vicinity of a mucous membrane of a palate of an oral cavity of the subject. A control unit is configured to drive the electrode to apply an electrical current to the mucous membrane, and to configure the current to be capable of inducing an increase in cerebral blood flow (CBF) of the subject. Other embodiments are also described.