Two-photon calcium imaging of the effects of cortical microstimulation

描述（由申请人提供）：世纪以来，人们已经知道施加到大脑的小电流可以激活神经元，触发运动并改变行为。近年来，脑刺激治疗神经系统疾病的应用激增。全世界有超过6万名失聪患者通过人工耳蜗植入恢复了听力。同样，脑深部电刺激已被证明在治疗包括帕金森氏症在内的顽固性运动障碍方面具有很高的价值。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。虽然电刺激目前在人类大脑植入物中被常规使用，但我们不知道电刺激如何改变大脑中的神经元活动。例如，关于脑深部电刺激是激活还是抑制目标区域的活动，存在着相当大的争论，因此，需要解决的根本问题是细胞群如何对电刺激做出反应。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招募的，还是有一个阈值，一组细胞对刺激做出反应？体内钙信号双光子成像的新技术为回答这些问题提供了一个独特的机会。通过这项技术，我们可以在施加电刺激时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几乎每个神经元受到刺激的影响，并为上述问题提供基本答案。我们有两个具体目标。首先，我们将使用单个电极刺激视觉皮层，并评估通过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。第二，我们将通过一个多位点电极刺激与紧密间隔的接触（50 - 5m的分离），并询问刺激效果如何随着电流注入的位置而变化。不同部位的刺激是否激活不同的细胞群，或者这些细胞群是否重叠？来自不同地点的响应是线性相加还是这些响应之间存在非线性相互作用？这些简单的协议将有助于地面50年的文献皮层刺激。更一般地说，这项工作将建立使用钙成像的协议，以校准神经回路中刺激的影响。对大脑的电刺激用于耳蜗植入以向聋人提供听觉，用于实验性视觉假体以向盲人提供视觉，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，在刺激过程中以高分辨率可视化大脑活动，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大脑疾病治疗方法。

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.