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Contribution of parallel inputs to speed tuning in higher visual cortex

并行输入对高级视觉皮层速度调节的贡献

基本信息

批准号：
10756417
负责人：
Helen Wang
金额：
$ 4.71万
依托单位：
UNIVERSITY OF CALIFORNIA, SAN DIEGO
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-07-01 至 2023-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10756417
关键词：
Contribution parallel inputs speed tuning

项目摘要

Abstract To encode visual information about our surroundings, the visual system uses neurons that respond to features of the visual world—light, color, contrast, movement, orientation, speed, direction, and more. At the earliest stages (retina, thalamus) of the visual system, these features consist of relatively simple properties, such as spatial or temporal modulation of light, that are encoded as parallel channels. At later stages (primary visual cortex (V1), extrastriate regions), these simple properties are combined to represent more complex visual features, such as orientation, direction, and speed. How cortical circuits combine parallel inputs of simple visual features and transform them into new complex visual features is incompletely understood. One transformation that is highly relevant to many species is the identification of the speed of visual motion. The speed of an object by definition requires the processing of at least two inputs- its spatial location and its temporal displacement. These parameters can be studied quantitatively by using drifting sinusoidal gratings that vary systematically in spatial frequency (SF) and temporal frequency (TF). Each combination of SF (cycles/degree) and TF (cycles/second) corresponds to a particular speed (TF/SF = speed, degrees/second). In the visual system, there are neurons that respond best when objects are moving at a particular speed; in other words, they are “speed tuned.” Some speed tuned neurons are thought to first emerge within V1. However, most are found in higher visual areas dedicated to motion processing. One hypothesis is that speed tuning emerges through a summation of offset SF and TF channels from V1 to higher visual areas. New transgenic and viral tools enabling cell type specificity as well as a recently improved understanding of the mouse visual system now make this a tractable hypothesis to test in mice. In mice, higher visual areas anterolateral (AL) and posteromedial (PM) are selectively tuned to different SFs, TFs, and speeds. AL is tuned to coarse features and fast speeds, while PM is tuned to fine features and slow speeds. Past studies have shown that AL and PM can inherit SF and TF tuning preferences from V1, but it is not known if they also inherit speed tuning or how speed tuning emerges. Preliminary data have also identified two cell populations in V1’s main thalamic input layer (layer 4) that are differentially tuned to SFs and TFs. This proposal hypothesizes that these V1 layer 4 populations represent parallel inputs that contribute differentially to the tuning of neurons in higher visual areas and the generation of speed tuning. The aims will first describe the speed tuning properties of V1, AL, and PM neurons in a laminar specific manner and evaluate the response properties of these layer 4 populations using awake in vivo extracellular electrophysiology and 2-photon calcium imaging. Finally, the hypothesis will be directly tested by selectively inactivating each layer 4 population and determining its effect on tuning in AL and PM. Together, these studies will have significant implications for understanding mechanisms of speed tuning in cortex and how complex sensory information is transformed across hierarchal cortical areas.

摘要为了对我们周围环境的视觉信息进行编码，视觉系统使用对特征做出反应的神经元光、颜色、对比度、运动、方向、速度、方向等等。尽早阶段（视网膜，丘脑）的视觉系统，这些功能包括相对简单的属性，如光的空间或时间调制，其被编码为并行通道。在后期阶段（主要视觉皮层（V1），纹外区），这些简单的属性相结合，以代表更复杂的视觉特征，例如方向、方向和速度。皮层回路如何联合收割机合并简单视觉的并行输入特征并将其转换为新的复杂视觉特征的方法尚未完全理解。一个与许多物种高度相关的转变是识别视觉运动的速度。的根据定义，物体的速度需要处理至少两个输入-其空间位置和其时间位移这些参数可以通过使用变化的漂移正弦光栅来定量研究系统地在空间频率（SF）和时间频率（TF）上。SF的每个组合（周期/度） TF（周期/秒）对应于特定速度（TF/SF =速度，度/秒）。在视觉系统中，当物体以特定速度移动时，神经元的反应最好;换句话说，它们是“快速调整”的一些速度调节神经元被认为首先出现在V1中。然而，大多数被发现在更高的视觉区域专门处理运动。一种假设是，速度调谐是通过从V1到更高视觉区域的偏移SF和TF通道的总和。新的转基因和病毒工具，细胞类型的特异性以及最近对小鼠视觉系统的理解的提高，现在使其成为一种在老鼠身上测试的简单假设。在小鼠中，前外侧（AL）和后内侧（PM）的较高视觉区域是选择性地调谐到不同的SF、TF和速度。AL被调整到粗糙的功能和快速，而PM是调整到精细的功能和缓慢的速度。过去的研究表明，AL和PM可以继承SF和TF调谐 V1的参数偏好，但不知道它们是否也继承了速度调整或速度调整是如何出现的。初步数据还确定了V1的主要丘脑输入层（第4层）中的两个细胞群，不同地调谐到SF和TF。该提议假设这些V1层4种群代表并行输入，有助于差异调谐神经元在更高的视觉领域和产生速度调谐目标将首先描述速度调谐特性的V1，AL和PM神经元在层流具体的方式，并评估这些层4群体的响应特性，使用清醒的体内细胞外电生理学和双光子钙成像。最后，该假设将被直接检验，选择性地使每个层4的布居失活并确定其对AL和PM中的调谐的影响。在一起，这些研究将对理解皮层的速度调谐机制以及如何进行速度调谐具有重要意义。复杂的感觉信息在等级皮层区域之间转换。