The signal data recordered on the scalp can be inverted to determine the underlying signals on the brain surface. The generalised Laplace equation describes the electrical activity within the human head and thus can be used in the inverse calculation to determine the underlying brain signals. This is known as the Inverse Problem.

Shown below is the head model consisting of the brain, skull and skin surfaces developed from a Magnetic Resonance Imaging (MRI) scan. The potential field on the surface of the scalp is also shown as well as the potential field on the brain surface obtained from the Inverse Procedure. The solution of the Inverse Problem can be evaluated by comparing the rerefered scalp signals (fitted_reref.signal) with the signals obtained from the Forward Problem (trans_head_data.signal) using UNEMAP.

MRI Head Model Front View with Field Back View with Field Brain Front View with Field Brain Back View with Field Comparison of the Forward and Referenced UNEMAP Scalp Signals

A movie sequence of the Inverse Problem can been seen in CMGUI by running the comfile view_inverse.com. This also calls the comfile animate_inverse.com as a looping comfile to generate a sequence of frames for a movie. The Forward Problem can been seen in CMGUI by running the comfile view_forward.com. This also calls the comfile animate_forward.com as a looping comfile to generate a sequence of frames for a movie.