Institute of Neuroscience, Université catholique de Louvain, Avenue Mounier 53, boite COSY B1.53.04, 1200, Brussels, Belgium.
Psychological Sciences Research Institute, Université catholique de Louvain, Louvain-la-Neuve, Belgium.
Exp Brain Res. 2023 Jul;241(7):1785-1796. doi: 10.1007/s00221-023-06637-2. Epub 2023 May 24.
To protect our body against physical threats, it is important to integrate the somatic and extra-somatic inputs generated by these stimuli. Temporal synchrony is an important parameter determining multisensory interaction, and the time taken by a given sensory input to reach the brain depends on the length and conduction velocity of the specific pathways through which it is transmitted. Nociceptive inputs are transmitted through very slow conducting unmyelinated C and thinly myelinated Aδ nociceptive fibers. It was previously shown that to perceive a visual stimulus and a thermo-nociceptive stimulus applied on the hand as coinciding in time, the nociceptive stimulus must precede the visual one by 76 ms for nociceptive inputs conveyed by Aδ fibers and 577 ms for inputs conveyed by C fibers. Since spatial proximity is also hypothesized to contribute to multisensory interaction, the present study investigated the effect of spatial congruence between visual and nociceptive stimuli. Participants judged the temporal order of visual and nociceptive stimuli, with the visual stimuli flashed either next to the stimulated hand or next to the opposite unstimulated hand, and with nociceptive stimuli evoking responses mediated by either Aδ or C fibers. The amount of time by which the nociceptive stimulus had to precede the visual stimulus for them to be perceived as appearing concomitantly was smaller when the visual stimulus occurred near the hand receiving the nociceptive stimulus as compared to when it occurred near the contralateral hand. This illustrates the challenge for the brain to process the synchrony between nociceptive and non-nociceptive stimuli to enable their efficient interaction to optimize defensive reaction against physical dangers.
为了保护身体免受物理威胁，整合由这些刺激产生的躯体和躯体外输入非常重要。时间同步是决定多感觉相互作用的一个重要参数，给定的感觉输入到达大脑所需的时间取决于它所经过的特定路径的长度和传导速度。伤害性输入通过非常缓慢传导的无髓鞘 C 和薄髓鞘 Aδ 伤害性纤维传递。先前的研究表明，为了感知同时施加在手上的视觉刺激和热伤害性刺激，对于由 Aδ 纤维传递的伤害性输入，伤害性刺激必须比视觉刺激提前 76 毫秒，而对于由 C 纤维传递的输入，则需要提前 577 毫秒。由于空间接近度也被假设为多感觉相互作用的贡献因素，本研究调查了视觉和伤害性刺激之间空间一致性的影响。参与者判断视觉和伤害性刺激的时间顺序，视觉刺激要么在受刺激的手旁边闪烁，要么在对侧未受刺激的手旁边闪烁，而伤害性刺激则通过 Aδ 或 C 纤维介导反应。当视觉刺激发生在接收伤害性刺激的手附近时，与发生在对侧手附近时相比，伤害性刺激必须提前视觉刺激多少时间，以便它们被感知为同时出现。这说明了大脑处理伤害性和非伤害性刺激之间同步性的挑战，以实现它们的有效相互作用，从而优化对身体危险的防御反应。
