Acoustic startle stimuli inhibit pain, but whether this is due to a cross‐modal inhibitory process or some other mechanism is uncertain. To investigate this, electrical stimulation of the sural nerve either preceded or followed an acoustic startle stimulus (by 200 ms) or was presented alone in 30 healthy participants. Five electrical stimuli, five acoustic startle stimuli, 10 startle + electrical stimuli, and 10 electrical + startle stimuli were presented in mixed order at intervals of 30–60 s. Effects of the startle stimulus on pain ratings, pupillary dilatation and nociceptive flexion reflexes to the electric shock were assessed. The acoustic startle stimulus inhibited electrically evoked pain to the ensuing electric shock (p < .001), and the electrical stimulus inhibited the perceived loudness of a subsequent acoustic startle stimulus (p < .05). However, the startle stimulus did not affect electrically evoked pain when presented 200 ms after the electric shock, and electrically evoked pain did not influence the perceived loudness of a prior startle stimulus. Furthermore, stimulus order did not influence the pupillary responses or nociceptive flexion reflexes. These findings suggest that acoustic startle stimuli transiently inhibit nociceptive processing and, conversely, that electrical stimuli inhibit subsequent auditory processing. These inhibitory effects do not seem to involve spinal gating as nociceptive flexion reflexes to the electric shock were unaffected by stimulus order. Thus, cross‐modal interactions at convergence points in the brainstem or higher centers may inhibit responses to the second stimulus in a two‐stimulus train.

中文翻译：

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声惊吓刺激抑制疼痛，但不改变对腓肠神经刺激的伤害性屈曲反射

声学惊吓刺激抑制疼痛，但这是否是由于跨模式抑制过程或其他一些机制尚不确定。为了研究这一点，对腓肠神经的电刺激要么在声学惊吓刺激之前或之后（200 毫秒），要么单独在 30 名健康参与者中进行。5 个电刺激、5 个声学惊吓刺激、10 个惊吓 + 电刺激和 10 个电 + 惊吓刺激以混合顺序以 30-60 秒的间隔呈现。评估了惊吓刺激对疼痛等级、瞳孔扩张和对电击的伤害性屈曲反射的影响。听觉惊吓刺激抑制了对随后的电击的电诱发疼痛（p < .001），并且电刺激抑制了随后的声学惊吓刺激的感知响度（p < .05）。然而，在电击后 200 毫秒出现时，惊吓刺激不影响电诱发疼痛，并且电诱发疼痛不影响先前惊吓刺激的感知响度。此外，刺激顺序不影响瞳孔反应或伤害性屈曲反射。这些发现表明，声惊吓刺激会暂时抑制伤害性处理，相反，电刺激会抑制随后的听觉处理。这些抑制作用似乎不涉及脊髓门控，因为对电击的伤害性屈曲反射不受刺激顺序的影响。因此，在脑干或更高中枢的会聚点处的跨模式交互可能会抑制对双刺激序列中第二个刺激的反应。