Differentiating between reflex and spontaneous blinks using simultaneous recording of the orbicularis oculi electromyogram and the electro-oculogram in startle research.

The present study documents the differences between reflex and spontaneous blinks by recording the vertical electro-oculogram (EOG) along with the orbicularis oculi electromyogram (OO-EMG). EOG and OO-EMG were applied without fixation of the head in 15 freely moving children during an auditory startle experiment. Results revealed that the easily-recorded EOG shows the same relationships between orbicularis oculi contraction and velocity of lid movement in startle blinks as the head-constraining methods, e.g. the magnetic search coil, used in previous studies. The OO-EMG onset occurred before the EOG onset in most reflex blinks while no such pattern occurred for spontaneous blinks. In comparison with spontaneous blinks, reflex blinks showed a shorter duration between onset and peak and between onset and offset in OO-EMG and EOG. In addition, reflex blinks showed greater OO-EMG activity and smaller EOG-recorded lid movements compared with spontaneous blinks. Simultaneous recording of OO-EMG and EOG can distinguish reflex from spontaneous blinks and lid saccades in populations, e.g. children, that cannot tolerate head restraint and in experiments permitting or requiring movement.