Two-photon calcium imaging of the effects of cortical microstimulation

描述（由申请人提供）：一个多世纪以来，人们已经知道，施加在大脑上的小电流可以激活神经元，触发运动并改变行为。近年来，脑刺激在神经系统疾病治疗中的应用出现了爆炸式增长。在世界范围内，超过6万名耳聋患者通过人工耳蜗恢复了听力。同样，脑深部刺激已被证明在治疗顽固性运动障碍（包括帕金森氏症）方面非常有价值。今天，它的用途正在扩大到各种严重的，否则无法治疗的疾病，包括难治性抑郁症，强迫症，甚至促进中风患者的功能恢复。虽然电刺激在人类大脑植入物中经常使用，但我们不知道电刺激是如何改变大脑中的神经元活动的。例如，关于深部脑刺激是否激活或抑制目标区域的活动，存在相当大的争论。因此，需要解决的基本问题是细胞群如何对电刺激作出反应。目标区域的所有细胞都被激活了吗？当电流增加时，细胞是一个接一个地被吸收，还是有一个阈值，一组细胞会对刺激做出反应？钙信号的体内双光子成像新技术为回答这些问题提供了一个独特的机会。有了这项技术，我们可以在电刺激下同时对数千个神经元的活动进行成像。因此，我们可以测量局部体积中的每个神经元是如何受到刺激的影响，并为上述问题提供基本答案。我们有两个具体目标。首先，我们将使用单电极刺激视觉皮层，并评估被各种电流和脉冲序列的微刺激激活（或抑制）的细胞的空间分布。其次，我们将通过一个具有紧密接触点（间隔50 5m）的多位点电极进行刺激，并询问刺激效果如何随着电流注入位置的变化而变化。不同部位的刺激是否激活了不同的细胞群，或者这些细胞群是否重叠？来自不同地点的反应是线性相加，还是这些反应之间存在非线性相互作用？这些简单的方案将有助于奠定50年来关于皮质刺激的文献。更一般地说，这项工作将建立使用钙成像来校准神经回路刺激效果的协议。脑电刺激用于耳蜗植入，为聋人提供听觉感觉，用于实验性视觉假体，为盲人提供视觉感觉，以及用于缓解帕金森病患者症状的治疗。我们提出的研究将使用一种新的成像技术来观察刺激过程中高分辨率的大脑活动，这在以前是不可能的。测量神经元对电刺激的反应将有助于设计出更好的脑部疾病治疗方法。

DESCRIPTION (provided by applicant): It has been known for over a century that small electrical currents applied to the brain can activate neurons, trigger movements, and change behaviors. Recent years have seen an explosion of applications of brain stimulation to the treatment of neurological disorders. Worldwide, more than 60,000 deaf patients have recovered hearing through cochlear implants. Similarly, deep brain stimulation has proven highly valuable in the treatment of intractable movement disorders including Parkinson's. Today, its use is being expanded to a variety of severe, otherwise untreatable disorders, including refractory depression, obsessive-compulsive disorders, and even to promote recovery of function in stroke patients. Although electrical stimulation is routinely used today in human brain implants, we do not know how electrical stimulation acts to change neuronal activity in the brain. There is considerable debate, for example, as to whether deep brain stimulation activates activity in the targeted area or whether it suppresses it. The fundamental issue to be addressed, therefore, is how populations of cells respond to electrical stimulation. Are all the cells in the targeted area activated? Are cells recruited one by one as current is increased, or is there a threshold at which a set of cells fire in response to stimulation? The new technique of in vivo two-photon imaging of calcium signals provides a unique opportunity to answer these questions. With this technology, we can image the activity of thousands of neurons simultaneously as electrical stimulation is applied. We can thus measure how virtually every neuron in a local volume is affected by stimulation, and provide basic answers to the questions posed above. We have two specific aims. First, we will use single electrodes to stimulate in the visual cortex and assess the spatial distribution of cells that are activated (or suppressed) by microstimulation with various currents and pulse trains. Second, we will stimulate through a multi-site electrode with closely spaced contacts (50 5m separation), and ask how stimulation effects vary as the location of the current injection is varied. Does stimulation at different sites activate different cell populations or do these populations overlap? Do responses from different sites sum linearly or are there nonlinear interactions between these responses? These simple protocols will help ground a 50- year literature on cortical stimulation. More generally, this work will establish protocols for the use of calcium imaging to calibrate the effects of stimulation in neural circuits. PUBLIC HEALTH RELEVANCE Electrical stimulation of the brain is used in cochlear implants to provide auditory sensation to the deaf, in experimental visual prostheses to provide visual sensation to the blind, and in treatments to relieve patients from the symptoms of Parkinson's disease. Our proposed studies will use a new imaging technique to visualize at high-resolution brain activity during stimulation, which has previously been impossible. Measuring how neurons respond to electrical stimulation will help devise better treatments for diseases of the brain.