Affect modulated startle reflex (AMSR) paradigm
The AMSR task was performed in an electrically shielded and soundproof chamber. Participants were given instructions on the paradigm and were told not to pay attention to the presented acoustic stimuli. Three different sets of color pictures were chosen from the International Affective Picture System (IAPS) based on their normative valence and arousal ratings (see Stable The AMSR was induced by binaurally presented acoustic startle probes consisting of 50 ms white noise bursts with instantaneous rise times. Sounds were generated with a soundcard (Soundblaster Audigy Rx) at a sampling rate of 44,100 Hz and presented binaurally via a pair of free field stereo loudspeakers (50 W) positioned at a distance of about 1.2 m in front of the subjects. The sound intensity of the probe at the location of the subject’s head was between 88- and 95-dB (A) sound pressure level, as measured by a handheld sound level meter. The onset time of startle probes was varied randomly between 3500 and 4500 ms after the picture onset on display. To decrease the predictability of the startle probes, for one trial in each valence category, acoustic probes were presented during SAM ratings instead of during picture viewing and for another one trial in each category acoustic probes were omitted. In total, 12 pictures per valence category were accompanied by acoustic probes in each session. In the beginning of each session, the acoustic probes were delivered during the presentation of habituation sets of 3 pictures (one picture per category). The startle responses during the viewing of the habituation set were not included in the analysis. The pictures and acoustic probes were delivered by using the Psychophysics Toolbox extensions in version 3