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

项目摘要 大脑是一个由相互连接的区域组成的复杂拼凑体，网络方法已经成为 对理解其功能架构越来越有用。静息态功能磁共振成像（rs-fMRI）已经出现， 非侵入性研究大规模功能网络的重要工具。然而， 已知负责形成rs-fMRI功能连接的神经元机制。这 知识对于解释rs-fMRI数据、因果建模大脑状态、预测行为和设计网络至关重要- 基于神经精神和神经系统疾病的治疗方案。在所有的大脑区域中，纹状体 可能是研究rs-fMRI神经起源的一个独特的例子。文献中的研究结果一再表明， 表明，在两个半球的纹状体rs-fMRI信号是高度同步的，但病毒追踪研究 双侧纹状体之间没有直接的解剖学联系。这就提出了一个有趣的问题-- 双侧纹状体rs-fMRI连接形成没有任何直接的解剖连接？处理这个问题 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 情景可以解释存在的纵裂纹状体rs-fMRI连接：（1）同步发射的 纹状体GABA能MSNs，（2）皮质-纹状体或丘脑-纹状体同步释放谷氨酸 黑质-纹状体投射的多巴胺同步释放。在这里，我们假设， (2)（3）是起源，（3）是最突出的来源。我们提出这样的假设是因为（1） 我们团队成员先前的严格研究表明，两个半球之间的MSN放电是 异步的，和（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个多- 通道，光谱分辨，MR兼容的纤维光度技术，是理想的破译神经 rs-fMRI的起源严格的先前研究已经证明了我们独特的能力，同时测量 在功能磁共振成像过程中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 主要的神经元成分，同时纤维光度法和功能磁共振成像在双侧纹状体。那些 组分是：（1）突触前多巴胺能释放;（2）突触前多巴胺能释放;和（3）突触前多巴胺能释放。 突触后钙加权神经元活动。我们假设大脑半球间纹状体功能磁共振成像 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，我们将询问 多巴胺能和多巴胺能投射对大脑半球间纹状体rs-fMRI连接的因果影响 使用化学遗传学。我们假设，沉默SNc中的单侧多巴胺活性可能会中断 大脑半球间纹状体rs-fMRI连接。我们将在纹状体单方面表达抑制性DREADD- 投射皮质神经元、MSN和黑质多巴胺神经元，并重复与中相同的实验 目的1研究DREADD激动剂去氯氯氮平（DCZ）治疗前后的变化。总之，这 该项目旨在解决有关大脑半球间纹状体神经相关性的重要知识缺失 功能磁共振成像连接。调查人员在这一领域的研究有着良好的记录，并将带来创新。 通过桥接局部细胞成像和分析方法来解决新的假设， 严格的前期研究。

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.