Hanson C L, Chen G, Ebner T J
Departments of Neuroscience and Neurosurgery, University of Minnesota, Minneapolis 55455, USA.
Neuroscience. 2000;96(2):317-31. doi: 10.1016/s0306-4522(99)00470-4.
The spatial patterns of activation in the rat cerebellar cortex evoked by ipsilateral face stimulation were mapped using optical imaging based on the pH sensitive dye, Neutral Red. The aims of the study were to characterize the optical responses evoked by peripheral stimulation and test the hypothesis that the resultant parasagittal banding is due to climbing fiber activation. In the anesthetized rat Crus I and II of the cerebellar cortex were stained with Neutral Red. Epi-fluorescent changes produced by a train of stimuli (5-10s and 4-20 Hz) to the ipsilateral face were monitored in time using a fast, high resolution charge-coupled device camera. The patterns of activation were quantified using a two-dimensional fast Fourier transform analysis that removed signals with high spatial frequencies and minimized the contribution of horizontal structural elements (i.e. blood vessels). The dominant spatial pattern of activation evoked by face stimulation was that of parasagittal bands. The bands were highly frequency-dependent and were elicited most strongly by stimulus frequencies in the range of 6-8 Hz. There was a large fall-off in the response for frequencies above and below. The optical signal evoked by face stimulation built up over a period of 10s and then gradually decayed. Within a folium the individual parasagittal bands exhibited some frequency and temporal specificity. Stimulation of the contralateral inferior olive also resulted in the activation of parasagittal bands with characteristics similar to the bands evoked by face stimulation, including a preferred stimulus frequency which peaked at 10 Hz. Injection of lidocaine into the contralateral inferior olive blocked the parasagittal bands evoked by ipsilateral face stimulation, while control injections of saline had no effect. The results confirm that a parasagittal banding pattern is a dominant feature of the functional architecture of the cerebellar cortex. The parasagittal banding pattern observed with Neutral Red is due primarily to the activation of climbing fiber afferents. The frequency tuning of the responses, with the preference for peripheral stimuli of 6-8 Hz, is in agreement with previous findings that the inferior olive is inherently rhythmic. These observations support the hypothesis that inferior olivary neurons are dynamically coupled into groups that activate parasagittal bands of Purkinje cells in the cerebellar cortex. The frequency tuning also supports the hypothesis that the climbing fiber system is involved with timing. Activation of this afferent system may require stimuli with appropriate frequency content and stimuli synchronized to the rhythmicity of the inferior olive.
利用基于pH敏感染料中性红的光学成像技术，绘制了同侧面部刺激诱发的大鼠小脑皮质激活的空间模式图。本研究的目的是表征外周刺激诱发的光学反应，并检验由此产生的矢状旁带是由攀爬纤维激活所致的假说。在麻醉的大鼠中，用中性红对小脑皮质的I小叶和II小叶进行染色。使用快速、高分辨率的电荷耦合器件相机实时监测同侧面部一系列刺激（5 - 10秒，4 - 20赫兹）产生的落射荧光变化。使用二维快速傅里叶变换分析对激活模式进行量化，该分析去除了高空间频率的信号，并将水平结构元素（即血管）的贡献降至最低。面部刺激诱发的主要激活空间模式是矢状旁带。这些带高度依赖频率，在6 - 8赫兹范围内的刺激频率诱发最强。高于和低于该频率范围时，反应有大幅下降。面部刺激诱发的光学信号在10秒内逐渐增强，然后逐渐衰减。在一个小叶内，各个矢状旁带表现出一定的频率和时间特异性。刺激对侧下橄榄核也会导致矢状旁带激活，其特征与面部刺激诱发的带相似，包括在10赫兹达到峰值的偏好刺激频率。向对侧下橄榄核注射利多卡因可阻断同侧面部刺激诱发的矢状旁带，而注射生理盐水作为对照则无效果。结果证实，矢状旁带模式是小脑皮质功能结构的主要特征。用中性红观察到的矢状旁带模式主要是由于攀爬纤维传入的激活。反应的频率调谐，偏好6 - 8赫兹的外周刺激，与之前关于下橄榄核固有节律性的研究结果一致。这些观察结果支持以下假说：下橄榄核神经元动态耦合成群，激活小脑皮质浦肯野细胞的矢状旁带。频率调谐也支持攀爬纤维系统参与时间调控的假说。该传入系统的激活可能需要具有适当频率成分且与下橄榄核节律同步的刺激。
