Cross-modal plasticity after the loss of vision at two early developmental ages in the posterior parietal cortex: Adult connections, cortical function and behavior.

哺乳动物的新皮层在一生中有着非凡的变化能力，特别是在早期阶段。 发展大脑皮层、感觉区域及其连接的发育依赖于 来自外周的感觉感受器的传入感觉输入。这种早期自发的感觉 输入，加上来自环境的感官体验，塑造了新皮层，以产生最佳的 行为我们从对人类和啮齿动物的研究中得知，早期视力丧失会导致大量的 大脑的变化;通常是视觉和后顶叶皮质区包含 只对躯体感觉和听觉刺激有反应的神经元。这个重组的枕叶皮层 接受来自丘脑核和与躯体感觉相关的皮层区域的异位输入， 听觉处理目前的建议解决了这些问题所提出的几个基本问题 以前的研究结果：1）失明的发病年龄如何不同地影响大脑皮层的连接， 后顶叶皮质内侧和外侧区（PPCL和PPCM）？2)有哪些 PPCM和PPCL的单神经元反应特性，以及失明开始的年龄是否影响 这些财产？3)PPCL的功能和解剖变化之间的关系是什么？ PPCM和由备用感觉系统介导的代偿行为？在这些 实验，高度后期发育的短尾负鼠（Monodelphis domestica）的双侧摘除 将在两个发育里程碑进行：1）在视网膜自发活动开始之前， 在视网膜膝状体轴突到达丘脑之前，以及在丘脑皮质轴突受到神经支配之前， 新皮质; 2）当视网膜中的自发活动正在进行并且视网膜小膝状体， 丘脑皮层轴突已经支配了它们的目标。摘除后，将在以下时间对动物进行评估： 这两个时间点使我们能够直接评估失明对重要发育的影响， 里程碑这些数据可以指导治疗干预，以弥补视力丧失， 针对高级皮层功能

The mammalian neocortex has a remarkable ability to change over a lifetime, particularly during early development. The development of the cortex, sensory fields and their connections are dependent on the incoming sensory inputs from the sensory receptors in the periphery. This early, spontaneous sensory input, together with sensory experience from the environment shapes the neocortex to generate optimal behavior. We know from studies in humans and rodents that early loss of vision leads to massive changes in the brain; what would normally be visual and posterior parietal cortical areas contains neurons that respond only to somatosensory and auditory stimulation. This reorganized occipital cortex receives ectopic input from thalamic nuclei and cortical fields associated with somatosensory and auditory processing. The current proposal addresses several fundamental questions raised by these previous findings: 1) How does the age of onset of blindness differentially impact cortical connectivity of the medial and lateral divisions of the posterior parietal cortex (PPCL and PPCM)? 2) What are the single-neuron response properties in PPCM and PPCL, and does the age of blindness onset impact these properties? 3) What is the relationship between functional and anatomical changes PPCL and PPCM and the compensatory behaviors mediated by the spared sensory systems? In these experiments, bilateral enucleations in the highly altricial short-tailed opossum (Monodelphis domestica) will be made at two developmental milestones: 1) Prior to the onset of spontaneous activity in the retina, before retinal geniculate axons reach the thalamus, and before thalamocortical axons have innervated the neocortex; 2) When spontaneous activity in the retina is ongoing and retinogeniculate and thalamocortical axons have innervated their targets. Following enucleations, animals will be assessed at two time points allowing us to directly assess the impacts of blindness at important developmental milestones. These data can direct therapeutic interventions to compensate for the loss of vision that targets higher-order cortical function.