A method is provided for facilitating a diagnosis of a condition of a
subject, including applying a current to a site of the subject selected
from the list consisting of: a sphenopalatine ganglion (SPG) of the
subject, and a neural tract originating in or leading to the SPG, and
configuring the current to increase conductance of molecules from brain
tissue of the subject through a blood brain barrier (BBB) of the subject
into a systemic blood circulation of the subject. The method also
includes sensing a quantity of the molecules from a site outside of the
brain of the subject, following initiation of application of the current.
