The neurophysiological basis of prolonged negative BOLD signals

一种名为血氧水平依赖(BOLD)功能磁共振成像(FMRI)的技术可以确定活着的人脑部分不同活动的水平，以及疾病中如何发生故障。然而，这项技术依赖于局部血液氧合的变化，而不是直接测量大脑中的电活动。人们已经开始了解大脑活动的增加是如何导致血液变化的，但活动减少是如何以及是否会影响大脑血氧的，根本没有被描述出来，这使得神经成像数据很难从大脑活动减少的角度进行解释。尽管存在这种不确定性，但科学家表示要使用功能磁共振成像来推断大脑活动的减少，如果这一推断是正确的，他们的研究表明，大多数精神疾病(如精神分裂症、严重抑郁障碍)、神经发育障碍(如自闭症)、神经疾病(如阿尔茨海默病？S)的特征是无法关闭？更确切地说？兴奋？脑力活动中特定的大脑区域。通过同时直接测量减少的脑活动、神经成像信号和血氧含量，我们希望了解它们之间的关系，并允许神经成像的这一重要方面进一步了解大脑功能及其在疾病状态下的故障。

A technique called blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) can determine levels of different activity in parts of the living human brain and how malfunctions can occur in disease. However, this technique relies on changes in local blood oxygenation rather than measuring the electrical activity in the brain directly. How increases in brain activity results in blood changes has started to be understood, but how and if decreases in activity affect brain blood oxygen is not at all characterised making neuroimaging data very difficult to interpret in terms of decreases in brain activity. Despite this uncertainty, scientists are stating to use FMRI to infer decreases in brain activity and if this inference is correct their studies suggest that the majority of psychiatric (e.g. schizophrenia, major depressive disorder), neuro-developmental (e.g. Autism) neurological (e.g. Alzheimer?s) brain diseases are characterised an inability to ?turn-off? rather ?turn-on? specific brain regions during mental tasks. By directly measuring reductions brain activity, neuroimaging signals and blood oxygen content at the same time we hope to understand the relationships between them and allow this vital aspect of neuroimaging to further our understanding of brain function and its malfunction in disease states.