Purpose: Temporal-structure discrimination is an essential dimension of tactile processing. Exploring object surface by touch generates vibrotactile input with various temporal dynamics, which gives diversity to tactile percepts. Here, we examined whether slow cortical potential shifts (SCPs) (<1 Hz) evoked by long vibrotactile stimuli can reflect active temporal-structure processing.

Materials and methods: Vibrotactile-evoked magnetic brain responses were recorded in 10 right-handed healthy volunteers using a piezoelectric-based stimulator and whole-head magnetoencephalography. A series of vibrotactile train stimuli with various temporal structures were delivered to the right index finger. While all trains consisted of identical number (15) of stimuli delivered within a fixed duration (1500 ms), temporal structures were varied by modulating inter-stimulus intervals (ISIs). Participants judged regularity/irregularity of ISI for each train in the active condition, whereas they ignored the stimuli while performing a visual distraction task in the passive condition. We analysed the spatiotemporal features of SCPs and their behaviour using the minimum norm estimates with the dynamic statistical parametric mapping.

Results: SCPs were localized to contralateral primary somatosensory area (S1), contralateral superior temporal gyrus, and contralateral as well as ipsilateral secondary somatosensory areas (S2). A significant enhancement of SCPs was observed in the ipsilateral S2 (S2i) in the active condition, whereas such effects were absent in the other regions. We also found a significant larger amplitude difference between the regular- and irregular-stimulus evoked S2i responses during the active condition than during the passive condition.

Conclusions: This study suggests that S2 subserves the temporal dimension of vibrotactile processing.

目的：时间结构辨别是触觉处理的一个基本维度。通过触摸探索物体表面会产生具有各种时间动态的振动触觉输入，这为触觉感知提供了多样性。在这里，我们检查了由长振动触觉刺激引起的缓慢皮层电位变化 (SCP) (<1 Hz) 是否可以反映活跃的时间结构处理。

材料和方法：使用基于压电的刺激器和全头脑磁图记录了 10 名右手健康志愿者的振动触觉诱发的磁脑反应。一系列具有各种时间结构的振动触觉列车刺激被传递到右手食指。虽然所有列车都由在固定持续时间 (1500 ms) 内传递的相同数量 (15) 刺激组成，但时间结构通过调节刺激间间隔 (ISI) 来改变。参与者在主动条件下判断每列火车的 ISI 规律性/不规律性，而他们在被动条件下执行视觉分心任务时忽略了刺激。我们使用最小范数估计和动态统计参数映射分析了 SCP 的时空特征及其行为。

结果： SCP 定位于对侧初级躯体感觉区 (S1)、对侧颞上回、对侧以及同侧次级躯体感觉区 (S2)。在活动条件下，在同侧 S2 (S2i) 中观察到 SCP 的显着增强，而在其他区域则没有这种影响。我们还发现，在主动条件下，与被动条件相比，规则刺激和不规则刺激引起的 S2i 反应之间的幅度差异显着更大。

结论：这项研究表明 S2 支持振动触觉处理的时间维度。