Mp150 for windows

The startle data were acquired using Biopac MP150 for Windows (Biopac Systems, Inc., Aero Camino, CA). The acquired data were filtered, rectified, and smoothed using MindWare software (MindWare Technologies, Ltd., Gahanna, OH), and exported for statistical analyses. Startle data were collected via recording of the eye-blink muscle contraction using the electromyography (EMG) module of the Biopac system. The startle potentiation was recorded with two 5-mm Ag/AgCl electrodes; one was placed on the orbicularis oculi muscle 1cm below the pupil and the other 1cm lateral to the first electrode. A common ground electrode was placed on the neck below the right earlobe. Impedance levels were less than 6 kilo-ohms for each participant. The startle probe was a 108-dB(A)SPL, 40ms burst of broadband noise delivered through headphones (Maico, TDH-39-P). The maximum amplitude of the eyeblink muscle contraction 20–200 ms after presentation of the startle probe was used as a measure of startle magnitude.

Biopac MP150 for Windows (Biopac Systems, Inc.) was used to collect electrocardiogram (ECG) data at a sampling rate of 1 kHz, amplified and digitized using the Biopac system. HR and HRV were processed using MindWare software (MindWare Technologies, Inc), which identifies ECG R-waves and R-R intervals (i.e., the time period between heart beats), and detects artifacts, which were manually inspected and corrected. HRV was derived by spectral analysis of one-minute epochs with a Hamming windowing function and log transformed. Given that our primary interest was in parasympathetic contributions to HR, we chose to examine high frequency HRV because it best represents parasympathetic nervous system activity (Malliani et al., 1991 (link), but also see Berntson et al., 1997 (link)). Settings for the high frequency band were based on standard recommendations for HRV data (0.12–0.40 Hz; Task Force, 1996 (link)), and transformed by natural log.

The electromyogram (EMG) data were acquired at a sampling rate of 1000 Hz using Biopac MP150 for Windows (Biopac Systems, Inc., Aero Camino, CA). The data were filtered, rectified, and smoothed in MindWare software (MindWare Technologies, Inc.) and exported for statistical analyses. EMG activity was recorded from two 5 mm Ag/AgCl electrodes placed over the orbicularis oculi muscle, approximately 1 cm under the pupil and 1 cm below the lateral canthus. The impedances for all participants were less than 6kΩ. The EMG signal was filtered with low- and high-frequency cutoffs at 28 and 500 Hz, respectively. Startle magnitude was assessed as the peak amplitude of the EMG contraction 20–200 ms following the acoustic startle probe, which was a 106-dB [A] SPL, 40-ms burst of broadband noise delivered binaurally through headphones.

Heart rate (HR) and heart rate variability (HRV) were measured through electrocardiogram (ECG) sensors using the Biopac MP150 for Windows (Biopac Systems, Inc, Goleta, CA) with the BioNomadix wireless ECG amplifier. The wireless amplifier allowed the women to wear the ECG leads continuously during the TSST. Three Ag/AgCl electrodes filled with electrolyte gel were attached to the torso in the lead II position. ECG were sampled at 1000 Hz and analyzed using MindWare HRV module (MindWare Technologies, Ltd, Gahanna, OH). The ECG signal was amplified by a gain of 2000, filtered with a Hamming windowing function, and with a 60-Hz notch filter. HRV was quantified during 1-minute intervals by spectral analysis of the time-sampled inter-beat interval series, according to the methods recommended by the Society for Psychophysiological Research Committee on HRV (Berntson et al., 1997 (link)). HF-HRV (RSA) was sampled from 0.12 to 0.40 Hz and was transformed by natural log. HR, RSA, and LF/HF ratio were measured from the 1-min intervals during a baseline pre-stressor time point and at three post-stressor timepoints that were separated by 15-minute intervals. Baseline and post-stressor timepoints T1 (15 min), T2 (30 min), and T3 (45 min) were used in the present study.