NONLINEAR PROCESSES AT INTERMEDIATE STAGES

描述（改编自申请人的摘要）：大量的神经 系统致力于视觉，我们对它知之甚少。特定 神秘是高于中间水平的功能， 视网膜的逐点处理，但低于相关的高水平 与物体和场景（我们意识到的实体）。在大脑中， 这些中间过程占据了大量的组织。中的方法 研究这些中间层次的建议是行为的;它建立了 基于关于多个并行“通道”或“分析器”的累积知识， 特别是对不同空间频率范围敏感的那些， 导向已经提出了两种不同类型的非线性过程， 我们和其他人，这大大提高了多重能力， 解释图案视觉现象的渠道。其中一个非线性是 空间的，可以模拟为“复杂的渠道”，其中有两个阶段， 线性滤波，其间具有整流型非线性。这 需要用非线性来解释“非傅立叶”模式的处理 (i.e.其空间傅立叶分量不容易与 观察者的表现）。另一类非线性依赖于 刺激的强度特性，包括非线性， 取决于亮度（例如，视网膜中的光适应）和对比度（例如， 对比度增益控制，这已经提出了视网膜和 皮质）。这里提出的研究将进一步研究的结构， 复杂的渠道，特别是调查之间的关系， 第一级和第二级过滤器的性能和可能的双折射 方向（和/或空间频率）之间的差异。研究还提出， 深入到强烈的非线性动力学，特别是由于 皮层中的通道间抑制，其可以很好地建模为 “常态化网络”。许多建议的研究使用纹理分离 我们以前使用过的任务--因为我们已经学得足够多了， 他们在一个严格的-但其他任务也提出了为了 一般性，因为它们可能更适合其他问题。

DESCRIPTION (Adapted from applicant's abstract): A large amount of the nervous system is devoted to vision and we understand little of it as yet. A particular mystery is the function of intermediate levels that are higher than the pointwise processing of the retina but lower than the high levels concerned with objects and scenes (entities about which we are conscious). In the brain, these intermediate processes occupy a grate deal of tissue. The approach in this proposal for studying these intermediate levels is behavioral; it builds on accumulated knowledge about multiple parallel "channels" or "analyzers", especially those sensitive to different ranges of spatial frequency and orientation. Two different kinds of nonlinear processes have been proposed, by us and others, which substantially increase the ability of the multiple channels to explain phenomena of pattern vision. One of the nonlinearities is spatial and can be modeled as "complex channels" which have two stages of linear filtering with a rectification-type nonlinearity in-between. This nonlinearity is needed to explain the processing of "non-Fourier" patterns (i.e. patterns whose spatial Fourier components are not easily related to the observer's performance). The other class of nonlinearity is dependent on the intensive properties of the stimulus and includes both nonlinearities that depend on luminance (e.g. light adaptation in the retina) and on contrast (e.g. contrast-gain controls, which have been proposed for the retina and the cortex). Research is proposed here that would further examine the structure of the complex channels, particularly investigating the relationship between first-stage and second-stage filters' properties and the possible opponency between orientations (and/or spatial frequencies). Research is also proposed into the dynamics of intensive nonlinearities, particularly that due to inter-channel inhibition in the cortex which can be well modeled as a "normalization network". Many of the proposed studies use texture-segregation tasks we have used before --because we have learned enough about them to use them in a rigorous--but other tasks are also proposed both for the sake of generality because they may be better suited for other questions.