Investigating cortical pathways with diffusion-tensor imaging (DTI) manganese-enhanced MRI and modern histological techniques in monkeys and humans

研究大脑解剖学过去意味着打开头骨，观察死后的大脑切片。研究活人的大脑连接并不是一个好的选择。由于死亡的神经细胞不能很好地运输染料和示踪剂，追踪人类大脑中的连接尤为困难。在实验动物中，神经元示踪剂在活体大脑中运输，但为了看到结果，必须牺牲动物。因此，磁共振成像（MRI）的最新发展使我们能够在活体大脑中无创地追踪连接，这让人非常兴奋。但这些技术通过对水或离子运动的影响间接测量解剖结构。因此，他们的结果需要通过侵入性神经解剖技术对动物的连接进行更详细和准确的测量来校准。我们将在猴子和人类身上进行成像实验。这些数据将与用更成熟、更精确的解剖技术在猴子身上获得的数据进行比较，以便更好地了解这些新方法究竟测量了什么。我们用这些方法研究的通路连接了有助于做出简单决定的神经元。想象一下打网球：当一个球向你飞来时，你必须先观察并决定它的方向，然后才能回击它。我们的感官收集我们周围世界的信息。通常，获得这些信息后的下一个阶段是决定如何处理它——我们做出决定。在网球的例子中，我们决定球可能的运动轨迹以及我们想要如何回应。最后，我们可能想要根据我们所看到的来执行这个动作。我们的大脑总是快速有效地将感觉信息转化为行动（也许不是每个人都适用于网球）。类似的过程可能是更深思熟虑、更缓慢的决策过程的基础，比如闻水果盘里的苹果，然后决定拿起哪个吃。我们的大脑被分成相互关联的区域，分别处理不同类型的感官信息，比如来自我们眼睛的视觉信息，来自我们皮肤的触摸信息。此外，大脑的不同部分负责控制我们的肌肉运动或语言反应。在这些感觉和运动区域之间，我们相信有一些大脑区域可以将信息转化为运动，包括那些帮助我们做出决定的运动。我们正在研究的一个区域是视觉系统的V5/MT区域，它对移动的物体特别敏感。我们想测试这个区域是否直接连接到另一个被称为LIP的区域，该区域被认为是决策的核心。另外，其他中间脑区也可能参与其中。我们将利用新的非侵入性核磁共振技术，使我们能够追踪大脑不同区域之间的联系。使用核磁共振成像特别有用，因为它可以让我们深入了解健康人以及患者（例如中风后）的大脑连接。对这些新技术测量结果的更好验证也可能意味着对动物大脑的解剖可以在不牺牲动物的情况下进行。

Studying brain anatomy used to mean opening up a skull and looking at post mortem brain slices. Not really a good option to study brain connections in living humans. Tracing connections in the human brain is particularly difficult because dead nerve cells do not transport dyes and tracers well. In experimental animals the neuronal tracers are transported in the living brain but to visualize at the results, the animal has to be sacrificed. Therefore, there has been tremendous excitement about recent developments in Magnetic Resonance Imaging (MRI) that allow us to trace connections non-invasively in the living brain. But these techniques measure anatomical structures indirectly by their effect on movement of water or ions. Therefore, their results need to be calibrated against more detailed and accurate measurement of connections with invasive neuroanatomical techniques in animals. We will carry out imaging experiments in monkeys and humans. These data will be compared with those obtained with more established and accurate anatomical techniques in the monkey in order to gain a better understanding about what these new methods exactly measure. The pathway we investigate with these methods connects neurons that contribute to making simple decisions. Imagine playing tennis: when a ball comes towards you, you have to look and decide on its approach before being able to hit it back. Our senses to gather such information about the world around us. Often, the next stage after getting this information is to decide what to do with it - we make a decision. In the tennis example, we decide which trajectory the ball is likely to take and how we would like to respond. Finally we may want to execute this movement based on what we have seen. Our brain accomplishes such transformations of sensory information into action fast and effectively all the time (maybe not for everybody with regards to tennis). Similar processes might underlie more deliberate, slower decision processes, like smelling apples in a fruit bowl and deciding which one to pick up to eat. Our brain is divided up into interconnected regions that deal separately with different types of sensory information, such as visual information from our eyes, touch information from our skin. In addition, various parts of the brain are responsible for controlling our muscles for movement or verbal responses. In between these sensory and motor regions, there are brain areas that we believe can transform the information into movements, including those that help us to make decisions. One area we are looking at is an area of the visual system, called area V5/MT, which is particularly sensitive to moving objects. We want to test whether this area is connected directly to another area, known as LIP that is believed to be central to decision-making. Alternatively other intermediate brain areas might be involved. We will take advantage of new non-invasive techniques in MRI that allow us to trace connections between different brain areas. Using MRI is particularly useful, as it can give us an insight into the connections of the human brain in healthy people as well as in patients, for instance after stroke. Better validation of what these new techniques measure could also mean that anatomy on animal brains could be done without the need to sacrifice the animal.