OPTIMAL EMG SIGNAL BANDWIDTH AND INTERELECTRODE DISTANCE FOR THE RECORDING OF ACOUSTIC, ELECTROCUTANEOUS, AND PHOTIC BLINK REFLEXES

The bandwidth for the recording of the orbicularis oculi blink reflex electromyogram (EMG) response is optimal when low-frequency artifacts, such as motion artifacts and cross-talk from other muscles, are maxim ally suppressed, whereas true EMG signal power is maximally retained. The optimal bandwidth was investigated for acoustic, electrocutaneous, and photic blink reflexes. Reflexes were recorded with varying bandwi dth and interelectrode distances of 12 and 36 mm. Power spectra of the EMG signals were calculated and compared with a theoretical spectrum of the uncontaminated EMG signal. For both electrode distances, the op timal bandwidth was on the average 28-500 Hz for acoustic and electroc utaneous blink reflexes and 12-500 Hz for photic blinks. Using photic stimuli, however, a high-pass filter frequency larger than 12 Hz (prob ably at least 30 Hz) in combination with occlusion of the eye will be necessary to avoid influences of retinal potentials. Given the optimal bandwidth, a larger electrode spacing may be expected to moderately i mprove the detectability of small blinks in all stimulus conditions.