The application relates to a device for applying a varying magnetic field to a body portion of a human subject (2806), the device comprising a treatment surface (2899) for application to the body portion, first and second permanent magnets (2802a, 2802b), a subunit coupled to the permanent magnets and operable to rotate the permanent magnets relative to the treatment surface and a logic that is configure to control a frequency of rotation of the permanent magnets. Methods and devices described herein use alternating magnetic fields to gently tune the brain and affect mood, focus and cognition of subjects.
