Plasticity of development of vision and of the mammalian visual pathways

视觉发育和哺乳动物视觉通路的可塑性

• 批准号: RGPIN-2015-03819
• 负责人: Mitchell, Donald
• 金额: $ 2.4万
• 依托单位: Dalhousie University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=631143
• 关键词: Plasticity; development; vision; mammalian; visual

The objective of my research is to understand how the development of the pathways in the brain that process vision, and vision itself, is influenced by what an animal sees early in life, the so-called nature-nuture issue with respect to vision. From studies on animal species that have visual systems organized like ours for accurate binocular depth perception (stereoscopic vision), it is known that there are so called “critical periods” in development during which abnormal visual input can effect the development of the visual pathways that result in visual impairments. More recently it has been shown that prior to birth the anatomical organization of the visual system develops according to a series of genetic instructions to a level that can be quite sophisticated. The blueprint established by genetic instructions provides the template that both allows and constrains the extent to which visual experience after birth can further influence development. A few years ago I introduced a new method to examine the role of experience in development by sequentially pitting two visual inputs against each other each day. For part of the day animals receive normal visual input while for the remainder they receive grossly abnormal input, in the form of visual input to just one eye. The first visual input matches the anatomical template established by genetic instruction at birth, while the other input does not. We reasoned that visual input that matches the template at birth would be favoured over the other. The results clearly favour this possibility; binocular visual input that amounted to just 30% of the total exposure outweighed or protected against much longer daily periods of monocular exposure to permit the development of normal visual acuity in both eyes as well normal appearance of the visual cortex. The same strategy will be used to establish the far more strict requirements for development of normal stereoscopic vision, the ability to use information from the two eyes to provide a vivid impression of depth as in 3-D movies. Another study will examine the requirements for development of normal visual acuity and stereoscopic vision in the presence of intermittent misalignment of the two eyes as occurs in strabismus (a” turned eye”) that will be simulated with prisms. We will follow-up to a recent unexpected finding of ours, that kittens placed in total darkness for 10 days before the age of 11 weeks suffer a severe but temporary loss of vision by determining some of the conditions such as the length of darkness under which this effects occur. As in my past studies, the vision of each eye for these various studies is evaluated by use of a jumping stand where kittens are required to jump for a food reward and petting to one of two stimuli placed side by side below them.

我研究的目的是了解大脑中处理视觉的通路的发展以及视觉本身如何受到动物在生命早期看到的东西的影响，即所谓的与视觉相关的自然-自然问题。通过对具有像我们这样组织的视觉系统以实现准确的双眼深度感知（立体视觉）的动物物种的研究，我们知道发育中存在所谓的“关键期”，在此期间，异常的视觉输入会影响视觉通路的发育，从而导致视力障碍。最近的研究表明，在出生之前，视觉系统的解剖结构根据一系列遗传指令发育到相当复杂的水平。遗传指令建立的蓝图提供了一个模板，既允许又限制出生后视觉体验进一步影响发育的程度。几年前，我引入了一种新方法，通过每天顺序地将两种视觉输入相互对比来检查经验在发展中的作用。一天中的部分时间，动物接收正常的视觉输入，而在其余时间，它们接收严重异常的输入，以仅一只眼睛的视觉输入的形式。第一个视觉输入与出生时遗传指令建立的解剖模板相匹配，而另一个输入则不然。我们推断，与出生时模板相匹配的视觉输入会比其他输入更受青睐。结果显然支持这种可能性；仅占总暴露量 30% 的双眼视觉输入超过或保护了每天更长的单眼暴露时间，从而使双眼能够发育出正常的视力以及视觉皮层的正常外观。同样的策略将用于对正常立体视觉的发展提出更严格的要求，即使用来自两只眼睛的信息来提供像 3D 电影中那样生动的深度印象的能力。另一项研究将检查在两眼间歇性错位的情况下发展正常视力和立体视觉的要求，如用棱镜模拟的斜视（“转动的眼睛”）中出现的情况。我们将跟进我们最近的一项意外发现，即在 11 周大之前，小猫被置于完全黑暗的环境中 10 天，会出现严重但暂时的视力丧失，我们将通过确定一些条件（例如发生这种影响的黑暗时间长度）来进行跟进。正如我过去的研究一样，这些不同研究中每只眼睛的视力都是通过使用跳跃台来评估的，小猫需要跳跃以获得食物奖励，并抚摸并排放置在它们下方的两个刺激物之一。