Figure 5

Experimental design. (A) Transient stimuli belonging to four different sensory modalities (nociceptive somatosensory, non-nociceptive somatosensory, auditory, and visual). (B) The experiment consisted of four blocks, and in each block, there were 80 trials with transient stimuli belonging to four different sensory modalities (nociceptive somatosensory, non-nociceptive somatosensory, auditory, and visual). In two blocks, sensory stimuli were delivered to subject’s left side, and in the other two blocks, sensory stimuli were delivered to subject’s right side. The order of sensory modalities was pseudo-randomized, and the order of stimulated sides was counterbalanced across subjects. After each sensory stimulus, an auditory tone was delivered randomly between 3 and 5 s to prompt subjects to rate the perceived intensity on the 0–10 NRS verbally. The inter-stimulus interval (ISI) varied randomly between 11 and 15 s, and the interval between two consecutive blocks was 5 min.