The electrode positions used for EOG recording depend on the application. When eye movement is being measured, two pairs of electrodes may be used – one to measure vertical deflection of the eyes and the other to measure horizontal deflection. The vertical channel electrodes are typically placed above and below one eye (on the upper cheek and just above the eye brow). The horizontal channel electrodes may be placed on either side of one eye, but they are more frequently placed on the outer side of both eyes (i.e. on the temples) which is more comfortable and generally produces much the same effect since the eyes typically rotate in unison.