Stable perception of external stimuli over time: oculo-motor and visual processing mechanisms

6亿年前，当生活在海底的动物开始移动时，它们面临着一个重要的进化挑战：一方面，自我移动具有明显的优势：例如，寻找新的食物来源和躲避捕食者。另一方面，它引入了对感官输入来源的模糊性。当你过马路时，你需要区分一个运动是由汽车的运动引起的（需要避免），还是由你过马路引起的被动运动（可以忽略）。任何不能正确识别感官刺激来源的动物都将面临进化上的劣势，并带来毁灭性的后果。成功解决这个问题的物种是通过跟踪它们的运动指令并将即将到来的运动通知感官系统来实现的。眼球运动是由运动系统引起的一种特殊感觉变化的典型例子。如果我们完全按照呈现在眼前的样子来感知世界，那么视觉场景就像是一系列频繁而大的跳跃，使它们之间的任何匹配尝试都是不可能的。对于视觉系统来说，能够区分由扫视引起的“跳跃”与外部世界的变化是至关重要的。人们认为，运动系统向感觉系统提供即将到来的运动的警告，中枢神经系统对此作出补偿机制的反应。来自猴子神经生理学的证据表明，大脑中有几个位置特别参与了眼运动系统和视觉之间的相互作用，即：猴子额叶皮层的额叶和辅助视野，顶叶皮层的几个部分和运动敏感区。我们对猴子新皮层中这些区域的精细组织原理有了大致的了解，但到目前为止，同样的原理还没有在人类皮层的同源区域中得到测试。这反映了标准人类神经成像技术固有的局限性。标准人类神经成像研究的空间分辨率过于粗糙，无法描述在猴子神经生理学中典型观察到的详细空间组织。超高场成像（7Tesla）有助于克服这些技术限制，提供比标准神经成像采集更好、更详细的信号。这些优势使得在低视场（1.5和3Tesla）下无法成像的更详细的研究成为可能，从而为在人类体内测试猴子神经生理学中描述的精细眼动处理原理提供了可能。

When the animals populating the floor of the ocean started moving 600 million years ago, they faced an important evolutionary challenge: on one hand self-motion carry clear advantages: for example, finding new sources of food and escaping predators. On the other hand, it introduces ambiguity about the source of a sensory input. When you are crossing the street, you need to differentiate whether a motion is caused by a movement of a car (that need to be avoided), or a passive movement caused by you crossing the street (which can be ignored).Any animal that failed to correctly recognize the source of a sensory stimulation would have faced an evolutionary disadvantage, with devastating consequences.The species that successfully solved this problem did so by keeping track of their movement commands and informing the sensory system about forthcoming movements. Eye movements are a paradigmatic example of a specific sensory change, induced by the motor system. If we were to perceive the world exactly as it is displayed if front of our eyes, the visual scene would seem a sequence of frequent and large jumps, making any matching attempts between them impossible. It is crucial for the visual system to be able to distinguish 'jumps' that are due to saccades as opposed to changes in the external world. It is believed that the motor system provides the sensory system with a warning of an upcoming movement, to which the central nervous system responds with a compensatory mechanism.Evidence from monkey neurophysiology shows that several brain locations are particularly involved in the interaction between the oculo-motor system and vision, namely: the frontal and supplementary eye fields in monkey frontal cortex, several portions of the parietal cortex and motion sensitive areas.We have a general understanding of the fine organizational principles of these areas in monkey neocortex, but the same principles have not been tested in homologue areas of human cortex, so far.This reflects limitations intrinsic to standard human neuroimaging techniques. The spatial resolution in standard human neuroimaging studies is too coarse to characterize the detailed spatial organization typically observed in monkey neurophysiology. Ultra-high field imaging (7Tesla) helps overcoming these technical limitations, providing better and more detailed signal than standard neuroimaging acquisition. These advantages allow for a more detailed investigation that is not possible to image at lower fields (1.5 and 3Tesla), opening the possibility to test in humans, in vivo, the fine oculomotor-processing principles described in monkey neurophysiology.