Deciphering neural origins of interhemispheric striatal resting-state functional connectivity using simultaneous chemogenetic fMRI and triple-spectral fiber photometry

项目总结 大脑是由相互连接的区域组成的复杂拼接，网络方法已经成为 对于理解其功能架构越来越有用。静息状态功能磁共振成像(rs-fMRI)作为一种新的成像技术应运而生 是对静态大规模功能网络进行非侵入性研究的重要工具。然而，几乎没有什么是 了解形成rs-fmri功能连通性的神经机制。这 知识对于解释rs-fmri数据、对大脑状态进行因果建模、预测行为和设计网络至关重要。 神经精神和神经疾病的基础治疗方案。在所有脑区中，纹状体 这可能是研究RS-fMRI神经起源的一个独特的例子。文献中的发现反复出现 结果显示，rs-fmri信号在两个半球的纹状体是高度同步的，但病毒追踪研究。 双侧纹状体之间没有直接的解剖联系。这引发了一个耐人寻味的问题-- 双侧纹状体rS-fMRI的连通性是否没有任何直接的解剖学联系？回答这个问题 可能对理解纹状体中的rs-fmri信号代表什么有重要意义。三种可能 情景可以解释大脑半球间纹状体rs-fmri连接的存在：(1)同步激发 纹状体GABA能MSN，(2)皮质纹状体或丘脑纹状体谷氨酸的同步释放 (3)黑质纹状体投射的多巴胺同步释放。在这里，我们假设 (2)和(3)是来源，其中(3)是最突出的来源。我们之所以形成这样的假设，是因为(1) 我们团队成员之前的严格研究表明，MSN在两个半球之间发射 (2)多巴胺神经元是众所周知的起搏细胞。我们的团队最近开创了一种多- 通道，光谱分辨率，与MR兼容的光纤光度技术，是破译神经的理想选择 RS-fmri的起源。严格的前期研究已经证明了我们同时测量的独特能力 在功能磁共振成像期间，多个大脑区域的多个荧光传感器活动。在目标1中，我们将测量三个 双侧纹状体主要神经元成分的同时纤维光度分析和功能磁共振成像。那些 成分是：(1)突触前谷氨酸能释放；(2)突触前多巴胺能释放；以及(3) 突触后钙加权神经元活动。我们假设大脑半球间的纹状体fMRI 连接性可能与纹状体中突触前多巴胺的释放有关。在目标2中，我们将审问 谷氨酸和多巴胺能投射对大脑半球纹状体rS-fMRI连通性的因果影响 使用化学遗传学。我们推测，抑制黑质单侧多巴胺活动可能会中断 大脑半球间纹状体rs-fmri连通性。我们将在纹状体单方面表达抑制性DREADD- 在MSN和黑质多巴胺神经元中投射皮质神经元，并重复相同的实验 目的1应用DREADD激动剂地氯氮平(DCZ)前后。总而言之，这是 该项目旨在解决关于大脑半球间纹状体神经相关的重大知识缺失问题 功能磁共振连通性。调查人员在这一研究领域有着良好的记录，并将带来创新 通过将局部细胞成像和分析方法连接到现场，解决得到良好支持的新假设 通过严格的事先研究。

PROJECT SUMMARY The brain is a complex patchwork of interconnected regions, and network approaches have become increasingly useful for understanding its functional architecture. Resting-state fMRI (rs-fMRI) has emerged as the prominent tool for non-invasive investigation of large-scale functional networks at rest. However, little is known about the neuronal mechanisms responsible for the formation of rs-fMRI functional connectivity. This knowledge is critical to interpret rs-fMRI data, causally model brain states, predict behavior, and design network- based treatment regimens for neuropsychiatric and neurological disorders. Among all brain regions, striatum may represent a unique example to study the neural origins of rs-fMRI. Findings in literature have repeatedly shown that rs-fMRI signals in the striatum of both hemispheres are highly synchronized, yet viral tracing studies showed no direct anatomical connections between bilateral striatum. This raises an intriguing question – how is bilateral striatal rs-fMRI connectivity formed without any direct anatomical connection? Addressing this question could have major implications in understanding what rs-fMRI signals in striatum represent. Three possible scenarios may explain the existence of interhemispheric striatal rs-fMRI connectivity: (1) synchronous firing of striatal GABAergic MSNs, (2) synchronous release of glutamate from cortico-striatal or thalamo-striatal projections, and (3) synchronous release of dopamine from nigro-striatal projections. Here, we hypothesize that (2) and (3) are the origins, with (3) being the most prominent source. We formed such a hypothesis because (1) rigorous prior study from our team members suggested that MSN firing between two hemispheres is asynchronous, and (2) dopamine neurons are well known pacemaker cells. Our team recently pioneered a multi- channel, spectrally resolved, MR-compatible fiber photometry technique that is ideal to decipher the neural origins of rs-fMRI. Rigorous prior research has demonstrated our unique ability to simultaneously measure multiple fluorescent sensor activities across multiple brain regions during fMRI. In Aim 1, we will measure three major neuronal components with simultaneous fiber-photometry and fMRI in bilateral striatum. Those components are: (1) presynaptic glutamatergic releases; (2) presynaptic dopaminergic releases; and (3) postsynaptic calcium-weighted neuronal activities. We hypothesized that interhemispheric striatal fMRI connectivity might be related to presynaptic dopamine releases in the striatum. In Aim 2, we will interrogate the causal influence of glutaminergic and dopaminergic projections on interhemispheric striatal rs-fMRI connectivity using chemogenetics. We hypothesized that silencing unilateral dopamine activity in the SNc may interrupt interhemispheric striatal rs-fMRI connectivity. We will unilaterally express inhibitory DREADD in striatum- projecting cortical neurons, in MSNs, and in nigral dopamine neurons, and repeat the same experiments as in Aim 1 before and after the administration of DREADD agonist deschloroclozapine (DCZ). In summary, this project aims to address significant missing knowledge about the neural correlates of interhemispheric striatal fMRI connectivity. The investigators have a strong track record in this line of research and will bring Innovation to the field by bridging local cellular imaging and analytical methods to address novel hypotheses well supported by rigorous prior research.