Apparatus and methods are described including placing a set of two or more electrodes (22) in electrical contact with a portion of a subject's body. At least one computer processor (24) drives the electrodes to apply an amplitude shift keying signal to the portion of the subject's body, the amplitude shift keying signal containing a high frequency component that acts as a carrier wave, the high frequency component having a frequency of between 80 Hz and 120 Hz, and a low frequency component that acts as a modulating component that modulates the carrier wave, the low frequency component having a frequency of between 1 Hz and 8 Hz. Other applications are also described.
