Functional Plasticity in Adult Visual Cortex

描述(由申请人提供)：依赖活动的可塑性对神经系统的发育和功能是必不可少的。在哺乳动物的新大脑皮层，感觉刺激在电路和功能的形成中起着至关重要的作用，这在很大程度上可能是通过活性依赖的突触修饰来调节的。虽然在每个水平-突触、回路和功能-皮质可塑性已经得到了广泛的研究，但不同水平的活动诱导的改变之间的因果关系仍有待确定。我们的目标是在这些水平上沟通对皮质可塑性的理解。在最近的研究中，我们已经证明，非同步视觉刺激(1-2分钟)可以诱导成人皮质感受野(RFs)和人类空间知觉的移动，这种方式与脉冲时序依赖可塑性(STDP)一致，STDP是一种在大脑兴奋性突触中广泛观察到的强大的突触学习规则。在这项拟议的研究中，我们将使用电生理和心理物理实验和计算模型相结合的方法，进一步研究STDP介导的成人视皮层的功能改变。有三个具体的目的，研究皮质可塑性的机制和功能意义。在目标1中，我们将测试视觉条件作用的短暂时间(秒)是否可以诱导RF和知觉的改变，这是最近在大脑皮层切片上的研究表明的一种可能性。这种快速可塑性可能在自然条件下更频繁地进行，本实验将为我们后续研究自然刺激诱导的皮质修饰提供基础。在目标2中，我们将研究功能修饰背后的神经元电路。我们将首先测量眼间转移的效果，以确定它是否起源于皮质。然后，我们将系统地研究皮层改变对条件参数(条件刺激的方向、亮度极性、时间和位置)以及记录的神经元的其他属性(简单/复杂分类、板层位置、双视性和方向选择性)的依赖性，以进一步确定潜在的电路。在目标3中，我们将通过测量运动刺激和包含运动信号的自然场景引起的皮质修改来直接评估可塑性的功能相关性。综上所述，这些研究可能为在皮质回路、射频特性和视觉感知水平上活动依赖的突触可塑性的功能含义提供重要的新见解。

DESCRIPTION (provided by applicant): Activity-dependent plasticity is essential for development and function of the nervous system. In the mammalian neocortex, sensory stimuli play crucial roles in shaping the circuitry and function, which may be largely mediated by activity-dependent synaptic modification. Although at each level - synaptic, circuitry, and functional - cortical plasticity has been studied extensively, the causal relationship between activity-induced modifications at different levels remains to be firmly established. Our goal is to bridge the understanding of cortical plasticity at these levels. In recent studies, we have demonstrated that asynchronous visual stimuli (1-2 min) can induce shifts in adult cortical receptive fields (RFs) and in human spatial perception in a manner consistent with spike-timing-dependent plasticity (STDP), a powerful synaptic learning rule widely observed among excitatory synapses in the brain. In the proposed study we will further examine the functional modifications of adult visual cortex mediated by STDP, using a combination of electrophysiological and psychophysical experiments and computational modeling. There are three specific aims, examining the mechanism and functional significance of the cortical plasticity. In Aim 1, we will test whether RF and perceptual modifications can be induced by brief periods (seconds) of visual conditioning, a possibility suggested by recent studies in cortical slices. Such rapid plasticity may operate more frequently under natural conditions, and this experiment will provide a basis for our subsequent studies of cortical modifications induced by natural stimuli. In Aim 2, we will investigate the neuronal circuitry underlying the functional modification. We will first measure the interocular transfer of the effect to determine whether it is cortical in origin. We will then examine systematically the dependence of the cortical modification on conditioning parameters (orientation, luminance polarity, timing, and location of conditioning stimuli) and on other properties of the recorded neuron (simple/complex classification, laminar location, binocularity, and direction selectivity) to further determine the underlying circuitry. In Aim 3, we will directly assess the functional relevance of the plasticity by measuring cortical modification induced by motion stimuli and by natural scenes containing motion signals. Together, these studies are likely to provide significant new insights into the functional implications of activity-dependent synaptic plasticity at the levels of cortical circuitry, RF properties, and visual perception.