Blink Reflex

Blink Reflex Latency

R-1 (BRL R-1): Specially constructed low voltage electromyographic amplifiers connected to a computer are placed on a non-conducting table. The subjects have surface (differential) electrodes attached over the upper and lower orbicular oculi muscles of both eyes. A ground electrode is placed on the mid-forehead or back of hand. They are seated comfortably in a dimly lit room and rest with their eyes gently closed (relaxed). Electromyographic (EMG) recordings are made from the lateral two thirds of the obicularis oculi muscles, bilaterally after tapping the supraorbital notches on the right and left. The differential EMG amplifiers permit low interference recording from electrodes without shielding.

The specially designed low voltage EMG amplifiers permitted electromyographs to be made in ordinary rooms even with fluorescent lights when proximity to major sources of electrical or magnetic fields such as power line transformers is avoided (1). For electrical stimulation, amplifiers are modified so the electrical stimulus died out within 8 ms so it did not interfere with the EMG signal. Electrical stimulation is generated by variable current amplitude and duration apparatus generally at 2.0 ms and 2.0 microamperes (MA). After preliminary testing showed that the order of electrical or mechanical stimulation did not bias outcome, mechanical stimulation which caused less pain and habituation preceded electrical testing in the 19 comparisons. Blink reflexes elicited by mechanical stimulation caused minimal discomfort to the subjects. A measurement series consists of 10 taps to the supraorbital notch on each side to elicit BRL R-1 right and left.

Reference Notes:

1. Kilburn KH, Thornton JC, Hanscom B: A field method for blink reflex latency R-1 (BRL R-1) and prediction equations for adults and children. Electromyo & Clin Neurophys 1996 in press.