Peri-Stimulus Time Histograms. PSTHs of eye blinks (light green and light blue) and eyelid twitches (dark green and dark blue) during the three experimental sessions (n = 5). Baseline Session 0: left column; Auditory Conditioning Session 1: center column; Silent Tapping Session 2: right column. The histogram bins were 40 ms wide; bars are stacked. The only condition with the US (airpuff) actually present have been highlighted in green (Please note that the y-axis [events per bin] in these green panels have been scaled down by a factor of 10 for display reasons, as the aversive stimulus generates a highly time-locked response in 100% of the presentations, thus creating much higher event counts in the respective time bin). The nontarget presentations (± 1, ± 2, ± 3, ± 4) have not been collapsed to one histogram, but have been ordered in four different rows in the graph with respect to their perceptual 'distance' to the target, i.e. frequency distance in the auditory session, and spatial distance on the piano keyboard in the motor session, respectively. The category "± 1" designates the neighboring key on the keyboard (to the left and right, respectively). The maximum distance to the target withing the 5-tone-space is ± 4. Non-musicians (NM) are depicted in the upper 5 rows and professional pianists (PP) in the lower five rows. t = 0 (dotted line) refers to tone (CS) onset or keystroke, respectively. The dashed line marks the onset of the airpuff (US, at t = 200 ms). Note that only during the Auditory Conditioning and only for the target tone the US was present (Green panels). Please note the presence of the two twitch-related peaks during Session 2 in the Pianist group.