Nausea can be severe.
Electrodes and recording devices. Nausea, vomiting, and dizziness. To measure involuntary eye movements, called nystagmus, in order to evaluate the function of the vestibular system and associated brain areas. How it works The electrical charge in the retina is slightly negative, while that in the cornea is positive. Electrodes placed on either side of the eye can measure the eye movements by picking up the displacement of the charges.