Mima T, Nagamine T, Nakamura K, Shibasaki H
Department of Brain Pathophysiology, Kyoto University School of Medicine, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.
J Neurophysiol. 1998 Oct;80(4):2215-21. doi: 10.1152/jn.1998.80.4.2215.
To clarify the role of primary and second somatosensory cortex (SI and SII) in somatosensory discrimination, we recorded somatosensory evoked magnetic fields during a stimulus strength discrimination task. The temporal pattern of cortical activation was analyzed by dipole source model coregistered with magnetic resonance image. Stimulus intensity was represented in SI as early as 20 ms after the stimulus presentation. The later components of SI response (latency 37.7 and 67.9 ms) were enhanced by rarely presented stimuli (stimulus deviancy) during passive and active attention. This supports an early haptic memory mechanism in human primary sensory cortex. Contra- and ipsilateral SII responses followed the SI responses (latency 124.6 and 138.3 ms, respectively) and were enhanced by attention more prominently than the SI responses. Active attention increased SII but not SI activity. These results are consistent with the concept of ventral somatosensory pathway that SI and SII are hierarchically organized for passive and active detection of discrete stimuli.
为阐明初级和次级体感皮层（SI和SII）在体感辨别中的作用，我们在刺激强度辨别任务期间记录了体感诱发磁场。通过与磁共振图像配准的偶极子源模型分析皮层激活的时间模式。刺激强度在刺激呈现后早在20毫秒时就在SI中得到体现。在被动和主动注意期间，SI反应的后期成分（潜伏期37.7和67.9毫秒）因极少呈现的刺激（刺激偏差）而增强。这支持了人类初级感觉皮层中的早期触觉记忆机制。对侧和同侧SII反应跟随SI反应（分别为潜伏期124.6和138.3毫秒），并且与SI反应相比，注意对其增强作用更显著。主动注意增加了SII而非SI的活动。这些结果与腹侧体感通路的概念一致，即SI和SII在层次上组织起来用于被动和主动检测离散刺激。
