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

视觉引导的扫视眼球运动的反应时间可以很好地监测空间注意的状态。当我们对膀胱视野中心的凝视点的注意力脱离，并扩散到视野的外围时，极短的潜伏期眼球运动(目标呈现后70-100毫秒)就会发生，称为快速眼跳。我们假设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，而捷径是从上丘浅层到深层的捷径。此外，我们假设乙酰胆碱能系统在促进SC内信号传递以执行快速眼跳方面起重要作用。为了验证这些假设，我们研究了(1)SC和…功能局部回路中的信号传递(2)向SC内注射乙酰胆碱相关物质(尤其是尼古丁)对扫视反应时的影响。(1)应用全细胞膜片钳记录技术，在大鼠SC切片上阐明了从视束(OT)到SC的中间层(SGI)存在一条通过浅层(SGS)和视层(SO)神经元的兴奋通路。兴奋性传递由AMPA和NMDA型谷氨酸受体共同介导，通常受到GABAA系统的强烈抑制。尼古丁通过直接作用于SC中间层的烟碱受体，诱导这些神经元的内向电流。此外，尼古丁的应用显著增强了OT-SGS/SO-SGI通路中的信号传递，这归因于尼古丁对SGI神经元的去极化。(2)将尼古丁(1-10 mM，1mul)注入猴SC的SGI(n=2)，表达扫视(潜伏期低于100毫秒)的频率显著增加。其机制可能是通过使SGI神经元去极化而绕过从SGS/SO到SGI神经元的捷径。我们正计划进一步研究乙酰胆碱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--桥脑脚核胆碱能神经元的表达眼跳发生和活动的影响。较少

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