Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, Saint Louis, MO 63104, USA.
Brain Res. 2010 Oct 21;1357:26-40. doi: 10.1016/j.brainres.2010.08.011. Epub 2010 Aug 11.
Optical recording techniques were applied to the turtle cerebellum to localize synchronous responses to microstimulation of its cortical layers and reveal the cerebellum's three-dimensional processing. The in vitro yet intact cerebellum was first immersed in voltage-sensitive dye and its responses while intact were compared to those measured in thick cerebellar slices. Each slice is stained throughout its depth, even though the pial half appeared darker during epi-illumination and lighter during trans-illumination. Optical responses were shown to be mediated by the voltage-sensitive dye because the evoked signals had opposite polarity for 540- and 710-nm light, but no response to 850-nm light. Molecular layer stimulation of the intact cerebellum evoked slow transverse beams. Similar beams were observed in the molecular layer of thick transverse slices but not sagittal slices. With low currents, beams in transverse slices were restricted to sublayers within the molecular layer, conducting slowly away from the stimulus site. These excitatory beams were observed nearly all the way across the turtle cerebellum, distances of 4-6mm. Microstimulation of the granule cell layer of both transverse or sagittal slices evoked a local membrane depolarization restricted to a radial wedge, but these radial responses did not activate measurable molecular layer beams in transverse slices. White matter microstimulation in sagittal slices (near the ventricular surface of the turtle cerebellum) activated the granule cell and Purkinje cell layers, but not the molecular layer. These responses were nearly synchronous, were primarily caudal to the stimulation, and were blocked by cobalt ions. Therefore, synaptic responses in all cerebellar layers contribute to optical signals recorded in intact cerebellum in vitro (Brown and Ariel, 2009). Rapid radial signaling connects a sagittally-oriented, fast-conduction system of the deep layers with the transverse-oriented, slow-conducting molecular layer, thereby permitting complex temporal processing between two tangential but orthogonal paths in the cerebellar cortex.
光学记录技术被应用于龟类小脑，以定位对其皮质层微刺激的同步反应，并揭示小脑的三维处理过程。首先将体外完整的小脑浸泡在电压敏感染料中，并将其完整时的反应与在厚小脑切片中测量的反应进行比较。每个切片都在其整个深度上被染色，尽管在 epi-illumination 期间脑回的上半部分看起来较暗，而在 trans-illumination 期间则较亮。光学反应被证明是由电压敏感染料介导的，因为诱发信号对于 540nm 和 710nm 光具有相反的极性，但对于 850nm 光没有反应。完整小脑的分子层刺激引发缓慢的横向光束。在厚的横向切片的分子层中观察到类似的光束，但在矢状切片中没有观察到。在低电流下，横向切片中的光束局限于分子层内的亚层，缓慢地从刺激部位传导。这些兴奋性光束在龟类小脑的几乎整个范围内都能观察到，距离为 4-6mm。无论是横向切片还是矢状切片的颗粒细胞层的微刺激都会引发局部细胞膜去极化，仅限于径向楔形，但这些径向反应不会在横向切片中激活可测量的分子层光束。矢状切片中（靠近龟类小脑的脑室表面）的白质微刺激激活了颗粒细胞和浦肯野细胞层，但没有激活分子层。这些反应几乎是同步的，主要位于刺激的尾部，并被钴离子阻断。因此，所有小脑层的突触反应都有助于在体外完整小脑（Brown and Ariel，2009）中记录的光学信号。快速的径向信号连接了深层的矢状定向、快速传导系统与横向定向、缓慢传导的分子层，从而在小脑皮质的两个切线但正交路径之间实现了复杂的时间处理。
