Physiological data recording and preprocessing
ExG
BRAIN
The startle electromyography (EMG) response was recorded bipolarly from two Ag/AgCl cup electrodes (1 cm diameter) placed over the lower orbital portion of the right orbicularis oculi muscle. Electrodes were filled with a conductive gel and attached to the skin by self-adhering washers and tape. Signals were recorded with a Brain Products ExG amplifier, digitized at 1 kHz sampling rate, and stored to disk. Offline preprocessing was performed using an in-house MATLAB script to filter and rectify the signal (see Supplement for details). Startle amplitude was defined as the difference between the peak startle and mean baseline amplitude (within 50 ms before probe onset). The raw startle amplitudes were then T-standardized (T