These measure the brain’s responses to stimuli that are delivered through sight, hearing or touch. These sensory stimuli evoke minute electrical potentials that travel along nerves to the brain and can be recorded with sensors (electrodes) that are attached to the scalp and skin at various sites. There are several types of evoked potentials:
Visual Evoked Responses (VER) – A visual stimulus (checkerboard pattern) stimulates the optic nerves and a response is recorded on a computer via multiple electrodes placed on your head over the visual cortex. You must remain alert throughout the test to prevent a false reading.
Somatosensory Evoked Potentials (SSEP) – Selected nerves are stimulated to detect any slowing in conduction in those nerve pathways. Only a slight electrical tapping sensation will be felt when each nerve is stimulated electrically and small electrodes are placed on your head to detect when the nerve impulses reach your brain.
Event-related Potentials (P300) – Electrodes are placed on your head to measure cognitive processing while you listen through headphones and concentrate on certain sounds. You do need to be alert and able to concentrate throughout this test.