CONTROL OF CENTRAL VISUAL PATHWAYS BY THE BRAINSTEM

视网膜-膝状体-皮质通路被认为是初级传入 在大多数哺乳动物中辅助视觉感知的通路。最近的证据 提示外侧膝状体核(LGN)在中枢神经系统中的重要作用 这条通路是对视觉信息的传输进行调制或门控 到视觉皮质。这种增益控制被认为反映了不同的 行为状态，如唤醒、注意力和眼球运动。一个消息来源 这种依赖状态的影响是脑干。三种方法是 提出用来描述在解剖和功能上 脑干和LGN，从而阐明了脑干和LGN的生理基础 状态依赖对视觉知觉的影响。 第一个目标是描述个体的光镜形态。 投射到LGN的脑干轴突。这将通过以下方式实现 在单独的实验中，注射新的顺行示踪剂--菜豆 寻常型亮氨酸凝集素(PHA-L)在体内的6个特定细胞群 脑干(臂旁核、蓝斑、中缝背核、 上丘、延髓旁核和视神经核 区域)，并按进程顺序重建PHA-L标记的过程 通过同侧LGN。这项技术提供了一种更优越的 从细小的轴突观察到的终末分支比 以前的顺行追踪法。第二个目标是延长PHA-L 技术发展到电子显微镜水平。特别是，我们将 澄清有关单个脑干轴突通过的回路的问题 影响LGN神经元。第三个目标是检查功能 这些脑干-LGN连接的后果。这将会实现的 通过观察电刺激或化学刺激对脑组织的影响 脑干对LGN细胞对GRG和LGN细胞胞外视觉反应的影响 斑点刺激。描述了分析刺激的影响的计划 三个脑干部位(臂旁核、蓝斑和背侧 中缝核团)对不同功能细胞类型的反应 LGN(例如，正常和滞后的X细胞，Y细胞，投射细胞， 中间神经元)和邻近的束旁核。

The retino-geniculo-cortical pathway is considered the primary afferent pathway that subserves visual perception in most mammals. Recent evidence suggests that an important role of the lateral geniculate nucleus (LGN) in this pathway is to modulate or gate the transmission of visual information to visual cortex. This gain control is thought to reflect different behavioral states such as arousal, attention and eye movements. One source of this state-dependent influence is the brainstem. Three approaches are proposed to describe the anatomical and functional connections between the brainstem and LGN, and thus, elucidate the physiological basis of the state-dependent influences on visual perception. The first aim is to describe the light microscopic morphology of individual brainstem axons that project to the LGN. This will be accomplished by injecting, in separate experiments, the new anterograde tracer, Phaseolus vulgaris leucoagglutinin (PHA-L) into six specific cell groups in the brainstem (parabrachial nucleus, locus coeruleus, dorsal raphe nucleus, superior colliculus, parabigeminal nucleus and the nucleus of the optic tract) and serially reconstructing PHA-L labelled processes as they course through the ipsilateral LGN. This technique provides a far superior visualization of the terminal arborizations from thin axons than any previous anterograde tracing method. The second aim is to extend the PHA-L technique to the electron microscopic level. In particular, we will clarify issues about the circuitry through which individual brainstem axons influence LGN neurons. The third aim is to examine the functional consequences of these brainstem-LGN connections. This will be accomplished by observing the effects of electrical or chemical stimulation in the brainstem on the extracellular visual responses of LGN cells to grating and spot stimuli. Plans are described to analyze the effects of stimulation in three brainstem sites (parabrachial nucleus, locus coeruleus, and dorsal raphe nucleus) on the responses of the different functional cell types in the LGN (e.g., normal and lagged X-cells, Y-cells, projections cells, interneurons) and the adjacent perigeniculate nucleus.