THALAMIC CONTROL OF CORTICAL VISUAL PROCESSING

外侧膝状体核（LGN）的层压模式 在解剖学上定义了几个平行的传入通道 信息传递到视觉皮层。 这一长期目标 项目是确定每个膝状体的贡献， 皮层生理学和视觉行为的细分， 在何种程度上以及在何种情况下， 通过膝状体层的信息被非- 视网膜输入，并获得更好的理解， 膝状体输入饲料的皮质内机制。 这项建议的第一个具体目标是确定 可逆灭活LGN的主要部分（A和C 层），在17区的活动和视觉行为， 醒着的猫 灭活将通过注射少量 大量盐酸利多卡因进入LGN， 试图注视小的视觉目标。 特别 兴趣是在多大程度上，活动在第4层和 颗粒上层通过该过程解离，并且 空间定向注意力与这种分离的相互作用。 膝状体失活的皮质和眼神经效应， 出现在伪随机位置的扫视目标将 与目标出现在预期的 位置. 第二个具体目标是检验收益 不同膝状体层的运动是动态和独立的 由中央反馈控制。 视网膜定位的单细胞 膝状体层A和C的相应部分将 同时记录，而动物正在执行相同的 用于特定目标1的可视化任务。 我们还将确定 膝状体兴奋性的中枢调节 在视网膜定位上仅限于视觉的关注区域 领域 第三个具体目标是检验假设，即 层间核（MIN）在微光视觉中具有特殊作用。 MIN的对比灵敏度和对比响应函数， 将在一定范围内与其他膝状体细胞进行比较 在麻醉猫的照明水平。

The lamination pattern of the lateral geniculate nucleus (LGN) anatomically defines several parallel channels of afferent information to the visual cortex. The long-term objectives of this project are to determine the contributions of each geniculate subdivision to cortical physiology and visuomotor behavior, to find out to what extent and under what circumstances the transmission of information through the geniculate layers is modulated by non- retinal inputs, and to obtain a better understanding of the intracortical mechanisms that geniculate inputs feed. The first specific aim of this proposal is to determine the effects of reversibly inactivating the main portion of the LGN (A and C layers), on activity in area 17 and on visuomotor behavior in awake cats. Inactivation will be accomplished by injecting small amounts of lidocaine hydrochloride into the LGN while the animal is attempting to fixate small visual targets. Of particular interest is the extent to which activity in layer 4 and in the supragranular layers is dissociated by this procedure, and the interaction of spatially-directed attention with this dissociation. The cortical and oculomotor effects of geniculate inactivation when the target of a saccade appears in pseudorandom locations will be compared with those when the target appears in an anticipated location. The second specific aim is to test the hypothesis that the gains of different geniculate layers are dynamically and independently controlled by central feedback. Single cells in retinotopically corresponding parts of geniculate layers A and C will simultaneously recorded while animals are performing the same visuomotor tasks used for Specific Aim 1. We will also determine the extent to which central modulation of geniculate excitability is restricted retinotopically to attended regions of the visual field. The third specific aim is to test the hypothesis that the medial interlaminar nucleus (MIN) has a special role in dim-light vision. Contrast-sensitivity and contrast-response functions of MIN and will be compared with those of other geniculate cells over a range of illumination levels in the anesthetized cat.