Control of focal brain stimulation with high-precision robotic aid

新技术使我们能够非常清晰地观察健康的人类大脑。然而，一个有点令人惊讶的观察结果是，不同的大脑区域经常显示出彼此相同的活动模式。例如，在一项研究中，你被要求将一个声音分类为单词或非单词，许多大脑区域可能会显示出更多的单词活动。所有这些大脑区域真的都在做同样的事情吗？解决这个问题的一种方法是看看当典型的大脑功能被破坏时会发生什么。神经科学家与患者群体合作，以找出哪些大脑区域对心理功能领域做出了关键贡献，这有着悠久的历史。例如，前额叶皮层的损伤可能会导致做出正确决策的挑战，这表明这个大脑区域对决策非常重要。然而，研究患者群体也有缺点。我们通常不知道到底有多少脑损伤，这使得定位变得困难。我们也不能选择病人在哪里以及如何受到脑损伤。然而，非侵入性脑刺激的方法能够解决其中的一些限制，并开辟了测试未受损大脑的可能性。其中一种方法是经颅磁刺激（TMS），这是一种安全有效的脑刺激形式。TMS使用短暂的磁脉冲来干扰局部区域（约5 mm）的大脑活动。我们可以应用这种刺激，看看参与者的行为在TMS期间或之后如何变化。TMS还可以与大脑活动的测量相结合，以帮助我们了解单个大脑区域如何调节整个大脑区域网络的活动。因此，TMS是当代认知神经科学的一种令人兴奋的方法。然而，有一些严重的实际约束TMS限制了该方法。关键的实际限制是刺激位置相对于参与者头部的一致性。在手动放置后，刺激器由实验者手动保持就位或由专门的机械臂保持就位。由于实验经常持续超过60分钟，因此几乎不可能始终保持相同的刺激器位置。实验者或参与者的微小动作可能意味着大脑中更大的区域受到了比预期更大的刺激。此外，很难测试两个彼此非常接近的大脑区域。为了解决这些问题，我们建议购买Axilum TMS机器人（ATR）。该设备自动放置刺激器，依靠大脑扫描（MRI）来确保准确性。重要的是，ATR将能够补偿参与者的任何头部运动，自动移动以确保维持刺激目标。ATR还有几个其他优点，例如提前准备刺激会话的能力。这可以帮助减少参与者在实验室中花费的时间，并提高我们运行整个实验的效率。我们的目标是利用ATR来回答一系列广泛的研究问题：1）我们能否使用大脑刺激来揭示帮助我们学习应对具有挑战性的感官环境的神经机制？2)前额叶皮层是如何帮助我们关注相关信息而忽略无关信息的？在这里，TMS将帮助我们区分前额叶皮层的不同区域，这些区域需要你注意视觉场景的不同部分。3)经颅磁刺激能否作为抑郁症和其他精神疾病的有效干预手段？4)支持准确的言语感知和产生的大脑活动顺序是什么？

New technologies have allowed us to look at the healthy human brain in action with remarkable clarity. A somewhat surprising observation, however, has been that different brain regions often show the same patterns of activity as each other. For example, in a study where you are asked to categorise a sound as either a word or non-word, lots of brain regions may show more activity for the word vs non-word. Do all these brain regions truly do the same thing? One way to solve this problem is to see what happens when typical brain function is disrupted. There is a long history of neuroscientists working with patients groups to find out which brain regions make critical contributions to domains of psychological function. For example, damage to the prefrontal cortex may lead to challenges in making good decisions, suggesting this brain regions is important for decision making. However, studying patients groups has drawbacks. We often don't know exactly how much brain damage there has been, making localisation difficult. We also don't get to choose where and how patients come to have brain injury. However, methods for non-invasive brain stimulation are able to address some of these limitations and open up the possibility of testing the non-damaged brain. One such method is transcranial magnetic stimulation (TMS), which is well-established as a safe and effective form of brain stimulation. TMS uses brief magnetic pulses to perturb brain activity in a localised region (~5mm). We can apply this stimulation and see how the behaviour of participants change during or after TMS. TMS can also be combined with measurements of brain activity, to help us understand how individual brain regions may modulate the activity of whole networks of brain regions. TMS is therefore an exciting method for contemporary cognitive neuroscience. However, there are some severe practical constraints on TMS that limit the method. The key practical limitation is the consistency of the stimulation position relative to the participant's head. The stimulator is either held manually in place by an experimenter or by a specialised mechanical arm, after manual placement. As experiments frequently last for over 60 minutes, maintaining the same stimulator position consistently is almost impossible. Small movements by either the experimenter or the participants can mean that much larger regions of the brain are stimulated than intended. Also, it is difficult to test two brain regions that are very close to each other. To solve these problems, we propose to purchase an Axilum TMS-robot (ATR). This equipment automates the placement of the stimulator, relying on a brain scan (MRI) to ensure accuracy. Importantly, the ATR will be able to compensate for any head movements from the participant, moving automatically to make sure the stimulation target is maintained. There are several further advantages of the ATR, such as the ability to prepare the stimulation session in advance. This can help to reduce the amount of time participants have to spend in the lab and increase the efficiency with which we can run the whole experiment. We aim to take advantage of the ATR to answer a broad range of research questions: 1) Can we use brain stimulation to reveal the neural mechanisms that help us learn to cope with challenging sensory environments? 2) How does the prefrontal cortex help us attend to relevant information and ignore irrelevant information? Here, TMS will help us differentiate between different regions of the prefrontal cortex in tasks that require you to attend to different parts of a visual scene. 3) Can TMS be used as an effective intervention for depression and other psychiatric conditions? 4) What is the sequence of brain activity that supports accurate speech perception and production?