Optimal EMG signal bandwidth and interelectrode distance for the recording of acoustic, electrocutaneous, and photic blink reflexes

Abstract

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 maximally 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 bandwidth 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 optimal bandwidth was on the average 28-500 Hz for acoustic and electrocutaneous blink reflexes and 12-500 Hz for photic blinks. Using photic stimuli, however, a high-pass filter frequency larger than 12 Hz (probably 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 improve the detectability of small blinks in all stimulus conditions.

Occipital Transcranial Magnetic Stimulation Has Opposing Effects on Visual and Auditory Stimulus Detection: Implications for Multisensory Interactions

“…The startle response was measured by recording the eyeblink reflex (Blumenthal et al, 2005). For this purpose, we recorded electromyographic (EMG) activity of the orbicularis oculi muscle bipolarly from two electrodes beneath the right eye (van Boxtel et al, 1998;Blumenthal et al, 2005). Electrode impedance was kept below 10 kOhm.…”

“…Offline EMG signal processing in the control experiment consisted of bandpass filtering (20 -500 Hz) (van Boxtel et al, 1998), rectifying of the signal (Blumenthal et al, 2005) and integration of the EMG activity from Ϫ100 to 0 ms before the auditory stimulus (to obtain baseline values) and from ϩ20 to 120 ms after the stimulus (area under curve) where eyeblink activity was maximal. Data were then subjected to a repeated-measure ANOVA with the factor sound-intensity (baseline, 65, 75, 85, 95 dB), followed by post hoc paired t tests where appropriate.…”

Emotional scenes and facial expressions elicit different psychophysiological responses

“…They were first filtered with a 50 Hz notch filter. To assess startle eyeblink responses the raw EMG signal was rectified, and frequencies below 20 Hz (van Boxtel et al, 1998) and above 500 Hz (Blumenthal et al, 2005) were filtered. The data were then integrated with time constants of 20 ms (for startle latency detection) and 100 ms (for peak amplitude detection).…”

Trait emotions and affective modulation of the startle eyeblink: On the unique relationship of trait anger.

“…EMG was recording from 4 mm Ag/AgCl electrodes placed over the left inferior orbicularis oculi below the inner and outer canthi (van Boxtel, Boelhouwer, & Bos, 1998), with a forehead ground. Impedances were below 10 kOhms.…”