CONTROL OF CENTRAL VISUAL PATHWAYS BY THE BRAINSTEM

视网膜-膝状体-皮质通路被认为是主要的传入 促进大多数哺乳动物视觉感知的途径。 最近的证据 表明外侧膝状体核（LGN）在 这条通路是调节或门控视觉信息的传输 视觉皮层 这种增益控制被认为反映了不同的 行为状态，如觉醒、注意力和眼球运动。 一个源 这种依赖于状态的影响的核心是脑干。 三种方法 提出来描述解剖和功能之间的联系， 脑干和LGN，因此，阐明的生理基础， 对视觉感知的状态依赖性影响。 第一个目的是描述个体的光镜形态 投射到LGN的脑干轴突。 这将通过 在单独的实验中，注射新的顺行示踪剂， 寻常白细胞凝集素（PHA-L）分为六个特定的细胞群， 脑干（臂旁核，蓝斑，中缝背核， 上级丘、二叠旁核和视神经核 道）和连续重建PHA-L标记的过程，因为他们的路线 穿过同侧LGN 这项技术提供了一个远远优于上级 从细轴突的终端分支的可视化比任何 以前的顺行追踪方法。 第二个目标是扩展PHA-L 电子显微镜技术水平。 特别是要 澄清关于个别脑干轴突通过电路的问题， 影响LGN神经元。 第三个目的是检查功能 这些脑干-LGN连接的后果 这将是完成 通过观察电刺激或化学刺激在 脑干对LGN细胞对光栅的细胞外视觉反应的影响 点刺激。 计划被描述来分析刺激的效果， 三个脑干部位（臂旁核、蓝斑和背侧核） 中缝核）对不同功能细胞类型的反应， LGN（例如，正常和落后的X细胞，Y细胞，投射细胞， 中间神经元）和邻近的膝状体周围核。

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.