Simons S B, Chiu J, Favorov O V, Whitsel B L, Tommerdahl M
Department of Biomedical Engineering, University of North Carolina, Chapel Hill, NC 27599, USA.
J Neurophysiol. 2007 Mar;97(3):2121-9. doi: 10.1152/jn.00513.2006. Epub 2006 Oct 11.
In previous studies, we showed that the spatial and intensive aspects of the SI response to skin flutter stimulation are modified systematically as stimulus amplitude is increased. In this study, we examined the effects of duration of skin flutter stimulation on the spatiotemporal characteristics of the response of SI cortex. Optical intrinsic signal (OIS) imaging was used to study the evoked response in SI of anesthetized squirrel monkeys to 25-Hz sinusoidal vertical skin displacement stimulation. Four stimulus durations were tested (0.5, 1.0, 2.0, and 5.0 s); all stimuli were delivered to a discrete site on the glabrous skin of the contralateral forelimb. Skin stimulation evoked a prominent increase in absorbance within the forelimb regions in SI of the contralateral hemisphere. Responses to brief (0.5 s) stimuli were weaker and spatially more extensive than responses to longer duration stimuli (1.0, 2.0, and 5.0 s). Stimuli >or=1 s in duration suppressed responses to below background levels (decreased absorbance) in regions that surrounded the maximally activated region. The magnitude of the suppression in the surrounding regions was nonuniform and usually was strongest medial and posterior to the maximally activated region. The results show that sustained (>or=1.0 s) stimulation decreases the spatial extent of the responding SI cortical population. Registration of the optical responses with the previously documented SI topographical organization strongly suggests that the cortical regions that undergo the strongest suppression represent skin sites that are normally co-stimulated during tactile exploration.
在先前的研究中，我们发现，随着刺激幅度的增加，体感皮层（SI）对皮肤颤动刺激的空间和强度方面会发生系统性改变。在本研究中，我们检测了皮肤颤动刺激的持续时间对SI皮层反应的时空特征的影响。利用光学内在信号（OIS）成像技术，研究了麻醉状态下松鼠猴的SI对25赫兹正弦垂直皮肤位移刺激的诱发反应。测试了四种刺激持续时间（0.5、1.0、2.0和5.0秒）；所有刺激均施加于对侧前肢无毛皮肤的一个离散部位。皮肤刺激在对侧半球SI的前肢区域内引起吸光度显著增加。与对较长持续时间刺激（1.0、2.0和5.0秒）的反应相比，对短暂（0.5秒）刺激的反应较弱且在空间上更广泛。持续时间≥1秒的刺激在最大激活区域周围的区域将反应抑制至背景水平以下（吸光度降低）。周围区域的抑制程度不均匀，通常在最大激活区域的内侧和后方最强。结果表明，持续（≥1.0秒）刺激会减小有反应的SI皮层群体的空间范围。将光学反应与先前记录的SI地形组织进行配准，强烈表明受到最强抑制的皮层区域代表了在触觉探索过程中通常会共同受到刺激的皮肤部位。
