Chung Yoon Gi, Han Sang Woo, Kim Hyung-Sik, Chung Soon-Cheol, Park Jang-Yeon, Wallraven Christian, Kim Sung-Phil
Department of Brain and Cognitive Engineering, Korea University, Anam-5ga, Seongbuk-gu, Seoul, 136-713, Republic of Korea.
Department of Biomedical Engineering, BK21+ Research Institute of Biomedical Engineering, College of Biomedical & Health Science, Konkuk University, Chungju, 380-701, Republic of Korea.
BMC Neurosci. 2015 Oct 29;16:71. doi: 10.1186/s12868-015-0207-x.
Tactile adaptation is a phenomenon of the sensory system that results in temporal desensitization after an exposure to sustained or repetitive tactile stimuli. Previous studies reported psychophysical and physiological adaptation where perceived intensity and mechanoreceptive afferent signals exponentially decreased during tactile adaptation. Along with these studies, we hypothesized that somatosensory cortical activity in the human brain also exponentially decreased during tactile adaptation. The present neuroimaging study specifically investigated temporal changes in the human cortical responses to sustained pressure stimuli mediated by slow-adapting type I afferents.
We applied pressure stimulation for up to 15 s to the right index fingertip in 21 healthy participants and acquired functional magnetic resonance imaging (fMRI) data using a 3T MRI system. We analyzed cortical responses in terms of the degrees of cortical activation and inter-regional connectivity during sustained pressure stimulation.
Our results revealed that the degrees of activation in the contralateral primary and secondary somatosensory cortices exponentially decreased over time and that intra- and inter-hemispheric inter-regional functional connectivity over the regions associated with tactile perception also linearly decreased or increased over time, during pressure stimulation.
These results indicate that cortical activity dynamically adapts to sustained pressure stimulation mediated by SA-I afferents, involving changes in the degrees of activation on the cortical regions for tactile perception as well as in inter-regional functional connectivity among them. We speculate that these adaptive cortical activity may represent an efficient cortical processing of tactile information.
触觉适应是感觉系统的一种现象，在暴露于持续或重复的触觉刺激后会导致暂时的脱敏。先前的研究报道了心理物理学和生理适应，即在触觉适应过程中，感知强度和机械感受传入信号呈指数下降。随着这些研究，我们假设在触觉适应过程中，人类大脑中的体感皮层活动也呈指数下降。本神经影像学研究专门调查了由慢适应I型传入神经介导的人类皮层对持续压力刺激的反应的时间变化。
我们对21名健康参与者的右手食指尖施加长达15秒的压力刺激，并使用3T MRI系统获取功能磁共振成像（fMRI）数据。我们分析了持续压力刺激期间皮层激活程度和区域间连接性方面的皮层反应。
我们的结果显示，在压力刺激期间，对侧初级和次级体感皮层的激活程度随时间呈指数下降，并且与触觉感知相关区域的半球内和半球间区域间功能连接也随时间呈线性下降或增加。
这些结果表明，皮层活动动态适应由SA-I传入神经介导的持续压力刺激，涉及触觉感知皮层区域的激活程度变化以及它们之间的区域间功能连接变化。我们推测这些适应性皮层活动可能代表了触觉信息的高效皮层处理。
