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Neurologic electrodes typically designed to measure the brain\'s electrical activity in response to visual stimulation (i.e. a change in luminance, contrast, or color). These electrodes are typically non-invasive small cup-like surface electrodes which are applied to the subject at the desired locations using either tape or water-soluble paste. The electrodes are connected to the main evoked potential unit (e.g., recorder, monitor) through a preamplifier and an electrode board allowing various channel-switching options. Reusable electrodes are available but disposable electrodes are more frequently used. Visual evoked potentials are generally obtained by delivering visual stimuli, including a flashing or strobe light in a number of different patterns that can elicit a visual evoked potential (VEP). The preferred stimulus is a reversing checkerboard pattern because normal subjects\' responses to it show less variability and are more sensitive to visual pathway lesions than responses elicited by a flashing light. Visual evoked potential electrodes are primarily used for clinical studies to measure the functional integrity of the visual pathways from the retina via the optic nerves to the visual cortex of the brain. Dedicated VEP electrodes may be used for measuring electrooculography and/or electronystagmography evoked potentials.
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