Amplitude-dependency of response of SI cortex to flutter stimulation.
Amplitude-dependency of response of SI cortex to flutter stimulation.
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DOI：
10.1186/1471-2202-6-43
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发表时间：
2005-06-21
期刊：
影响因子：
2.4
通讯作者：
Tommerdahl, M
中科院分区：
文献类型：
--
作者：
Simons, SB;Tannan, V;Chiu, J;Favorov, OV;Whitsel, BL;Tommerdahl, M
研究表明，颤振刺激的振幅越大，颤振刺激的感知强度越大。尽管许多研究已经对这一现象进行了研究，但刺激强度在初级体感皮层（SI）中编码的方式仍不清楚。采用光学本品信号（OIS）成像技术研究了25 Hz正弦垂直皮肤位移刺激对麻醉松鼠猴SI的诱发反应。刺激时间为10秒，刺激间隔为50秒。刺激幅值在50 ~ 400 μ m之间，不同幅值相互交错。在没有刺激的情况下测量控制水平的活动，并用于与不同刺激幅度引起的激活水平进行比较。刺激前肢的一个离散皮肤部位引起对侧半球细胞结构区3b和1的前肢代表性区域的吸收显著增加。刺激幅度的增加导致3b和1区的吸光度增加幅度成比例增加，而周围皮层的吸光度下降。相关图显示，随着刺激幅度的增加，SI激活区域的空间范围保持相对恒定，该区域内的活动逐渐增加。此外，当刺激幅度增加到阈值以上水平时，激活的SI区域周围的活动减少，表明这些区域内神经元活动的抑制增加。增加颤振刺激的振幅导致SI前肢表征区域内吸光度成比例增加。这很可能反映了该区域神经元放电率的增加。这种刺激引起的吸光度增加的相对恒定的空间范围表明，25 Hz皮肤刺激振幅的增加不会引起更大面积的SI神经元激活，这是由于振幅依赖的侧抑制效应在空间上引导了响应的SI神经元群。
It is established that increasing the amplitude of a flutter stimulus increases its perceived intensity. Although many studies have examined this phenomenon with regard to the responding afferent population, the way in which the intensity of a stimulus is coded in primary somatosensory cortex (SI) remains unclear. Optical intrinsic signal (OIS) imaging was used to study the evoked responses in SI of anesthetized squirrel monkeys by 25 Hz sinusoidal vertical skin displacement stimulation. Stimuli were 10 sec duration with a 50 sec inter-stimulus interval. Stimulus amplitude ranged from 50 to 400 microns and different amplitudes were interleaved. Control levels of activity were measured in the absence of stimulation, and used to compare with activation levels evoked by the different stimulus amplitudes. Stimulation of a discrete skin site on the forelimb evoked a prominent increase in absorbance within the forelimb representational region in cytoarchitectonic areas 3b and 1 of the contralateral hemisphere. An increase in stimulus amplitude led to a proportional increase in the magnitude of the absorbance increase in this region of areas 3b and 1 while surrounding cortex underwent a decrease in absorbance. Correlation maps revealed that as stimulus amplitude is increased, the spatial extent of the activated region in SI remains relatively constant, and the activity within this region increases progressively. Additionally, as stimulus amplitude is increased to suprathreshold levels, activity in the surround of the activated SI territory decreases, suggesting an increase in inhibition of neuronal activity within these regions. Increasing the amplitude of a flutter stimulus leads to a proportional increase in absorbance within the forelimb representational region of SI. This most likely reflects an increase in the firing rate of neurons in this region of SI. The relatively constant spatial extent of this stimulus-evoked increase in absorbance suggests that an increase in the amplitude of a 25 Hz skin stimulus does not evoke a larger area of SI neuronal activation due to an amplitude-dependent lateral inhibitory effect that spatially funnels the responding SI neuronal population.
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