Dipole models of eye movements and blinks

Average EOGs were recorded from 4 subjects for vertical and horizontal eye movements of 15 degrees away from and back to a central fixation point, and for eyeblinks while looking at the fixation point. Using spatio-temporal dipole modelling, several alternative dipole models of the electrical activity of the eyes were compared. A reasonable fit was only obtained if the equivalent dipoles were allowed to take up different locations and orientations depending on the type of eye activity. It appears that (a) the equivalent ocular dipole is located away from the axis of rotation of the eyeball, (b) eyelid movements contribute to a change in location of the dipole in vertical eye movements and blinks, and (c) some of the apparent dipole movement is due to inadequacy of the 3-shell spherical head model near to the eyes. Consequences of the results for eye-artifact correction are discussed.