Analysis of visuo-motor transformation process in the tecto-reticulo-spinal system.

视觉引导下的扫视眼动反应时可以很好地监测空间注意状态，当我们对视野中心注视点的注意力脱离，分散到视野周边时，对周边呈现的目标会发生极短潜伏期的扫视眼动（呈现目标后70- 100 msec），称为快速扫视。我们假设快速眼跳是视觉输入通过中枢神经系统的捷径直接激活运动输出系统而发生的，捷径是从上级丘（SC）的浅层到深层。为进一步证实乙酰胆碱能系统在SC执行快速眼跳的信号传递中起重要作用，我们研究了（1）SC局部环路的信号传递和功能 ...更多信息 （2）SC内注射乙酰胆碱相关物质（尤其是尼古丁）对扫视反应时间的影响。(1)用全细胞膜片钳技术记录大鼠SC脑片，阐明了SC存在一条从视束（OT）经表层（SGS）和视（SO）神经元到中间层（SGI）的兴奋通路。兴奋性传递由AMPA和NMDA型谷氨酸受体介导，并通常受到GABAA系统的强烈抑制。尼古丁通过直接作用于SC中间层神经元中的烟碱受体，在这些神经元中诱导内向电流。此外，尼古丁的应用显着增强OT-SGS/SO-SGI通路的信号传递，这是由尼古丁的SGI神经元的去极化损耗。(2)当将烟碱（1- 10 mM，1 μ l）注射到猴SC的SGI中时（n=2），快速扫视的频率（潜伏期低于100毫秒）显著增加。本研究拟进一步探讨乙酰胆碱受体拮抗剂对视觉引导扫视任务中支配SC的胆碱能纤维的输入来源--脚桥被盖核（pedunclulopontinetegmentnucleus，PCN）胆碱能神经元活性的影响。少

Reaction time of visually guided saccadic eye movements can be a good measure to monitor the state of spatial attention.When our attention on a fixation point in the center of our vesual field is desengaged, and becomes diffused on the periphery of the visual field, extremely short-latency saccadic eye movements (70-100msec after presentation of the target), called express saccades, occur to targets presented in the periphery. We have hypothesized that the express saccades take place when the visual input directly activate the motor output system by taking the short-cut pathway in the central nervous system, and the short-cut pathway is that from the superficial layr to the deeper layrs of the superior colliculus (SC). Furthermore, we hypothesized that acetylcholinergic system plays the dey role in facilitating the signal transmission in the SC to execute the express saccades.To prove these hypotheses, we investigated (1) signal transmission in the local circuit of the SC and function … More of acetylcholinergic input by using slice preparations obtained from rats, and (2) effect of injection of acetylcholine-related substance (especially nicotine) into the SC on saccadic reaction time.(1) We have clarified that there exists an excitatory pathway from the optic tract (OT) to the intermediate layr (SGI) of the SC via neurons in the superficial (SGS) and optic (SO) layrs by suing whole cell patch clamp recording technique in the SC slices obtained from rats. The excitatory transmission in mediated by both AMPA and NMDA type glutamate receptors, and usually under strong suppression by the GABAA system. Nicotine induces inward currents in neurons in the intermediate layr of the SC,by direct action on the nicotinic receptors in these neurons. Furthermore, application of nicotine dramatically enhanced the signal transmission in the OT-SGS/SO-SGI pathway, which was attriuted to the depolarization of the SGI neurons by nicotine.(2) When nicotin (1-10mM,1mul) is injected into the SGI of the monkey SC (n=2), frequency of express saccades (latency below 100 msec) dramatically increased. The mechanisms was supposed to be bypassing the short-cut pathway from the SGS/SO to the SGI neurons by depolarizing the SGI neurons.We are further planning to investigate the effect of acetylcholine antagonists on occurrence of express saccades and activity of cholinergic neurons in the pedunclulopontine tegmental nucleus, which is the input origin of the cholinergic fibers innervating the SC during visually guided saccade task. Less