Interrogation of Eye Movement Circuits using fMRI and Optogenetics

描述(申请人提供)：在神经影像文献中，关于所测量的血氧水平依赖信号(BOLD)和神经元抑制之间的关系，有很大的认识空白。基底节中控制眼球跳动抑制和释放的回路提供了一个独特的机会来填补这一知识空白。我们建议研究BOLD信号在激活参与眼动控制的抑制电路时的反应。我们将把编码光激活离子通道ChR2的基因插入到基底节的输出核中，使它们表达ChR2。提供给通道表达神经元的光源将打开离子通道，并导致抑制神经元的神经元去极化。大胆的信号将被衡量出来。我们有一个特定的目标：确定BOLD信号对参与眼动控制的抑制性神经回路的激活做出反应。为了实现这一目标，我们将进行三个实验。1)利用神经元特异性启动子CAG，我们将在黑质网状部神经元表达ChR2，并利用功能磁共振技术测量光激活对BOLD的反应；2)利用抑制性神经元特异性启动子(PV和GAD67)，我们将在黑质抑制性神经元表达ChR2，并利用功能磁共振技术测量光激活反应中BOLD信号；3)我们将记录上丘和丘脑(黑质抑制靶)对光激活的电活动(LFPS)，以比较光激活对电反应的BOLD反应。这些实验的结果将揭示神经处理抑制的关键机制，以及这种基本的神经元活动如何出现在粗体信号中。

DESCRIPTION (provided by applicant): In the neuroimaging literature, there is a large gap in knowledge regarding the relationship between blood oxygen level dependent signals (BOLD) that are measured and neuronal inhibition. The circuits in the basal ganglia that control the suppression and release of saccadic eye movements provide a unique opportunity to fill this gap in knowledge. We propose to study BOLD signals in response to activation of an inhibitory circuit involved in eye movement control. We will insert genes encoding the light-activated ion channel, ChR2 into an output nucleus of the basal ganglia causing them to express ChR2. A light source provided to the channel- expressing neurons will open ion channels and cause neuronal depolarization of inhibitory neurons. BOLD signals will be measured. We have one Specific Aim: to determine BOLD signals in response to activation of an inhibitory neural circuit involved in eye movement control. We will perform three experiments to achieve this aim. 1) Using the neuron-specific promoter CAG, we will express ChR2 in neurons of the substantia nigra pars reticulata (nigra) and measure BOLD responses to light activation using fMRI; 2) using inhibitory neuron-specific promoters (PV and GAD67) we will express ChR2 in inhibitory nigral neurons and measure BOLD signals in response to light activation using fMRI; 3) we will record the electrical activity (LFPs) in the super colliculus and the thalamus (targets of nigral inhibition) in response to light activation to compare BOLD responses to electrical responses. The results of these experiments will uncover critical mechanisms of neural processing of inhibition and how this fundamental neuronal activity appears in BOLD signals.