摘要
功能磁共振成像(functional magnetic resonance imaging,fMRI)通过检测血氧水平依赖(blood oxygen level dependent,BOLD)信号来探究大脑的神经活动,是研究神经科学和神经精神病学中人类大脑功能的一种重要技术.该技术的应用通常聚焦于血管分布相对密集的大脑灰质皮层区域中,而非脑深部的白质区域.然而,近年来随着白质BOLD信号生理意义的揭示,研究者逐渐将目光投向白质f MRI研究中.这些研究通过对白质BOLD信号进行分析发现,它们是由神经活动产生而非噪声或伪影引起,且白质和灰质具有相似的生理起源和意义.研究发现,外界刺激可以使白质区域激活,且白质区域存在与灰质皮层类似的功能网络.白质-灰质功能连接研究也进一步揭示了白质和灰质之间存在功能交互.随后的临床研究发现,患者大脑中普遍表现出异常的白质活动,其功能网络也发生了病理性的改变,且患者的功能障碍可能与白质和灰质之间的信息交流异常有关.尽管白质f MRI提供了一种直接探究和评估大脑白质功能的方法,但白质功能研究仍然处于初步探索阶段.由于分析手段限制,大脑深部白质结构的功能性研究仍相对较少,未来的研究需要给出一套规范的、适合于白质fMRI研究的分析方法,以便于相关研究的深入开展.
Functional magnetic resonance imaging(f MRI),a noninvasive imaging technology,measures metabolism and hemodynamics during brain activity based on blood oxygen level-dependent(BOLD) signals that indirectly reflect neural activity.Since the technique was proposed,it has been widely used in studies of cognitive neuroscience and clinical neuropsychiatry.The finding that BOLD signals between the bilateral sensorimotor cortices and other brain regions in the resting state had high temporal correlations led to the concept of functional connectivity being proposed.The functional connectivity method measures the degree of connection between different brain regions,revealing the functional integration of the brain,and has vigorously promoted the development of f MRI research.To date,however,f MRI applications usually focus on the cortical gray matter of the brain,in which blood vessels are relatively dense,rather than the deep white matter regions.The reasons are mainly attributed to the following two points.First,the vascular density,blood flow and blood volume are lower in white matter than in gray matter;thus,BOLD signal changes are much weaker.Second,white matter contains fewer postsynaptic potentials,which is the main source of BOLD signals.As a result,the reliability and biophysical origin of the white matter BOLD signal have always been controversial,and the BOLD signals from white matter have often been treated as noise in previous f MRI studies.In recent years,with the revelation of the physiological significance of BOLD signals in white matter,researchers have gradually turned their attention to f MRI studies of white matter.Through analysis,these studies have found that BOLD signals in white matter are generated by neural activity rather than by noise or artifacts and that white matter and gray matter have similar physiological origins and significance.It was demonstrated that external stimulation could activate white matter regions and that the white matter had functional networks similar to the gray matter cortex.Therefore,future studies should explore more activation patterns of white matter under tasks to further reveal the potential relationship between white matter function and individual behavior and cognition.In addition,the study of functional connectivity between white matter and gray matter further revealed functional interactions between them.Subsequent clinical studies found that patients generally showed abnormal white matter activity in the brain and pathological changes in its functional networks and that the dysfunctions in patients may also be related to abnormal communication between white matter and gray matter.Although white matter f MRI provides a direct method to investigate and evaluate white matter function,this research is still at a preliminary exploratory stage.At present,the function of deep brain white matter is rarely studied due to the limitations of analytic methods.Hence,future studies on white matter f MRI need to provide a set of normative and appropriate analytic methods to facilitate the in-depth development of related research.
作者
孙芬芬
陈悦
洪文军
赵智勇
Fenfen Sun;Yue Chen;Wenjun Hong;Zhiyong Zhao(Center for Brain,Mind,and Education,Shaoxing University,Shaoxing 312000,China;Department of Rehabilitation Medicine,Nanjing Drum Tower Hospital,the Affiliated Hospital of Nanjing University Medical School,Nanjing 210008,China;College of Biomedical Engineering&Instrument Science,Zhejiang University,Hangzhou 310027,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2021年第32期4074-4080,共7页
Chinese Science Bulletin
基金
国家自然科学基金(82001907)资助。
关键词
功能磁共振成像
血氧水平依赖
白质
功能
functional magnetic resonance imaging
blood oxygen level dependent
white matter
function
