Mr compatible physiological monitoring system

The MR-compatible physiological monitoring system (Biopac Systems; Goleta, CA) was also used to collect eye-blink electromyography (EMG) data. EMG was sampled (10 kHz) with a pair of disposable radio-translucent electrodes (1 cm diameter, Biopac Systems; Goleta, CA) from the orbicularis oculi muscle below the left eye. The first electrode was placed directly below the left pupil while the second was placed laterally to the first electrode as per previous committee report guidelines (Blumenthal et al., 2005 (link)). EMG data were processed using Biopac AcqKnowledge 4.1 software. Following guidelines for digital filtering (Cook and Miller, 1992 (link)) and EMG denoising (Blumenthal et al., 2005 (link)) a Fast Fourier Transform was used to assess and remove frequency domains where noise occurred (Comb Band Stop filter at fMRI fundamental frequency ≈ 17.0 Hz, 60 Hz Notch filter, 28–400 Hz Kaiser-Bessel Band Pass filter). The EMG signal was resampled at 1000 Hz then rectified and integrated (20 ms time constant) for scoring. Responses were scored as the peak-valley difference with the valley (average EMG response) occurring in the first 20 ms prior to the UCS and the peak occurring within the 21–150 ms window following the UCS (Blumenthal et al., 2005 (link)). Negative responses were scored as a zero.

An MR-compatible physiological monitoring system (Biopac Systems; Goleta, CA) was used to collect skin conductance response (SCR) data. SCR was sampled (10 kHz) with a pair of disposable radio-translucent dry electrodes (EL509, Biopac Systems; Goleta, CA). Isotonic recording electrode gel (Gel101, Biopac Systems; Goleta, CA) was applied to the electrodes which were then affixed to the thenar and hypothenar eminences of the left palm. SCR data were processed using Biopac AcqKnowledge 4.1 software. A 1 Hz low pass digital filter was applied and SCR data were resampled at 250 Hz. Unconditioned SCRs were limited to those that occurred within 10 s following the UCS presentation. Unconditioned SCRs smaller than 0.05 μSiemens were scored as 0. Data were then square root transformed prior to statistical analyses.