Non-invasive measurement of neural inhibition in the human visual cortex

大脑必须不断地在复杂的世界中筛选，以将相关信息从背景噪音中分离出来。大脑通过抑制不相关的信号来实现这一壮举-有时是有意识地通过使用注意力，但通常是无意识地通过神经回路中的低级过程。当我们更好地理解大脑如何对我们的经验做出反应时，我们越来越需要了解抑制如何调节大脑的反应。这是一个重大挑战。虽然现在可以使用功能性磁共振成像（fMRI）等非侵入性方法来测量大脑活动，但我们不知道如何类似地测量抑制。我们最近发现了一种潜在的抑制指数。使用一个我们知道抑制发生的模型，我们发现当抑制发生时，大脑的fMRI反应会稍微延迟。因此，我们认为这种延迟可以作为一种压制措施，并试图详细研究它。具体来说，我们需要知道是什么导致了明显的延迟--是两个空间上分离的信号的相关性，我们无法看到，因为我们的成像方法的分辨率，还是由于大脑在给定时间的神经化学组成？这种延迟是否发生在其他抑制模型中，是否有同样的原因？不管其原因是什么，延迟是否携带了相关信息，可以帮助我们了解潜在的神经回路？为了回答这些问题，这项研究计划将改进高分辨率的功能磁共振成像方法，并结合自然和人工刺激大脑来调节抑制，将能够回答这些问题。这些结果将对我们测量和解释大脑信号的方法以及理解抑制在自然处理过程中是如何参与和调节的方法产生变革性影响。

The brain must constantly sift through a complex world to separate relevant information from background noise. The brain achieves this feat by suppressing irrelevant signals--sometimes consciously through use of attention, but often unconsciously through low-level processes in neural circuits. As we gain a better understanding of how the brain responds to aspects of our experience, we increasingly need to understand how suppression modulates the response of the brain. This is a major challenge. While it is now possible to measure activity in the brain using non-invasive methods such as functional magnetic resonance imaging (fMRI), we do not know how to measure suppression similarly. We have recently discovered a potential index of suppression. Using a model where we know suppression occurs, we have found that the fMRI response of the brain is slightly delayed when suppression is engaged. We therefore think that this delay could serve as a measure of suppression, and seek to study it in detail. Specifically, we need to know what causes the apparent delay--is it a correlate of two spatially separate signals that we cannot see because of the resolution of our imaging method, or is it due to the neurochemical makeup of the brain at a given time? Does the delay occur in other suppression models, and do the same causes contribute to it? Regardless of its causes, does the delay carry relevant information that can help us understand the underlying neural circuits? To answer these questions, this program of research will refine high-resolution fMRI methods and, combined with natural and artificial stimulation of the brain to modulate suppression, will be able to answer these questions. The results will be transformative in both our approach to measuring and interpreting brain signals and in understanding how suppression is engaged and modulated during natural processing.