精神分裂症空间工作记忆任务的fMRI研究

目的采用fMRI技术探讨精神分裂症患者空间工作记忆损害的神经机制。方法收集18例精神分裂症患者和18名正常受试者进行空间n-back任务的fMRI扫描。采用SPM 8进行数据预处理和统计分析,单样本t-检验用于分析两组各自脑激活结果,双样本t-检验用于工作记忆相关脑激活的组间比较。采用FDR方法进行多重比较校正。利用SPSS 17.0软件对工作记忆任务中的行为学结果 (正确率和反应时间)进行组间比较。结果与对照组相比,精神分裂症患者空间工作记忆任务反应时间延长(882.00±50.31)ms,正确率下降(83.60±2.90)%(P0.05)。精神分裂症患者在n-back空间工作记忆任务时所激活的脑区分布与对照组基本一致,主要包括双侧前额皮层、颞顶叶皮层及部分基底核团。但组间比较显示精神分裂症患者多个脑区激活强度及范围明显增加,包括双侧前额皮层背外侧、双侧后顶叶皮层、右侧中央前回、左侧颞中回、右扣带回和双侧小脑(FDR校正,P0.05)。结论执行空间工作记忆任务时精神分裂症患者脑区激活增加,但行为学表现下降,提示患者脑区活动效率低下,可能是工作记忆能力损害的神经基础。     

缺陷型及非缺陷型精神分裂症执行功能障碍的fMRI初步研究

目的比较缺陷型、非缺陷型精神分裂症患者与执行控制功能有关的脑区激活情况,探讨精神分裂症执行功能障碍的表现规律与相应脑机制。方法缺陷型、非缺陷型精神分裂症患者各6名及与之匹配的正常对照组,在执行参量设计的倒数n项实验时进行全脑BOLD-fMRI扫描。数据处理时采用单因素方差分析进行差异检测,分离出激活强度随记忆负荷增加而增强的脑区（执行加工相关脑区）。结果正常组执行加工相关脑区主要为左侧前额叶及顶叶后部皮层,两精神分裂症组前额叶激活体积相对较小,而且涉及更多皮层下结构。其中非缺陷型组双侧前额皮层均显著激活,且背外侧前额叶（BA9/46区）激活数目较正常组明显增多。而缺陷型组无论是前额皮层激活的脑区分布范围还是体积均显著减少于其他两组。结论精神分裂症患者存在以前额叶功能失调为基础的执行功能障碍。不同亚型的患者前额叶功能失调的机制不同：缺陷型患者前额叶可能存在特异性损伤,而非缺陷型患者主要表现为前额叶的生理低效能。     

应用基于体素的形态测量学分析工作记忆老化的脑灰质萎缩基础

目的利用基于体素的形态测量学(VBM)方法探讨老年人工作记忆能力衰退与脑灰质萎缩间的关系。方法在30名老年人(老年组)和38名青壮年人(对照组)中分别进行keep-track任务和2-back任务两种工作记忆任务检测。对所有受试者进行高分辨力MR扫描,并使用统计参数图(SPM)8软件进行VBM分析,比较老年组与对照组的脑灰质体积差异,并在老年组内利用多元回归分析寻找与工作记忆任务能力下降相关的责任萎缩脑区。结果与对照组相比,老年组工作记忆能力显著衰退,且出现广泛的脑灰质萎缩。老年组中,与keep-track任务能力相关的萎缩脑区主要位于双侧前额叶中下部、运动前区、顶叶后下部和小脑;与2-back任务相关的萎缩脑区主要位于左侧的前额叶下部、运动前区和颞叶。左腹侧运动前区(BA6)皮层的灰质体积与两个任务的行为学数据均存在显著相关性。结论老年人工作记忆能力下降与工作记忆神经网络的灰质萎缩有关。     

轻度血管性认知障碍患者计算能力的功能MRI研究

目的利用功能MRI（fMRI）探讨轻度血管性认知障碍（MVCI）患者与正常老年人计算能力的差异,为MVCI患者的诊断提供依据。材料与方法对22例MVCI患者与12例正常老年人进行20以内减法计算时的fMRI,用SPM5处理得出脑激活图,比较正常老年人组和患者组的脑区激活情况和额、顶叶偏侧化现象,用两个独立样本t检验和Mann-Whitney检验比较两组的反应时间和正确率。结果患者的正确率明显低于正常老年组（χ2=18.6,P〈0.001）,反应时间明显延长（t=3.676,P〈0.05）。患者在双侧的顶上、下小叶（顶下小叶为主）,双侧额中回、双侧海马、海马旁回、右侧扣带回后部、双侧颞中回、左侧颞下回、双侧枕叶和双侧小脑激活减弱（P〈0.005）,未见激活增强脑区（P〈0.005）。患者和正常老年组右利手者的额、顶叶在减法计算时均体现左侧偏侧化现象。正常老年组的顶叶左侧偏侧化程度高于额叶,而MVCI组则相反。结论血管性认知障碍患者的计算功能已有不同程度的损害,存在一定的代偿,但仍表现为功能减弱。计算功能的fMRI研究能为诊断MVCI提供参考依据。     

前额叶在老年人吞咽中作用的任务态功能磁共振研究

目的 通过任务态功能性磁共振（fMRI）技术观察老年人的吞咽活动和认知网络,分析两者关系。 方法 选取13名健康老年人,年龄61～82岁,蒙特利尔认知评估量表（MoCA）评分≥26分,吞咽造影检查（VFSS）显示吞咽时无渗漏、误吸,行吞咽和认知任务态fMRI,分析两任务的激活脑区。 结果 吞咽和认知任务存在共同的激活脑区,即双侧小脑、枕叶、中央前回、中央后回、额中回、下顶叶等。吞咽任务中右侧前额叶正激活,左侧前额叶大部分为负激活,而认知任务中双侧前额叶均为正激活,且吞咽任务感觉区的激活范围大于运动区。 结论 老年人吞咽活动中右侧前额叶更具优势,右侧前额叶为吞咽和认知活动共同的神经节点。     

汉字情景记忆时皮层定位的fMRI研究

目的探讨用功能磁共振成像(fMRI)检测汉字情景记忆时皮层定位的价值及皮层定位的双侧不对称性.方法 10名健康右利手成人,以高频双字汉字作为刺激任务,行全脑fMRI,确定激活皮层的定位.结果汉字情景记忆时双侧多个脑区有激活,但两侧激活脑区不完全对称,编码加工时主要激活脑区为左侧纹外区和左侧颞叶梭状回,而提取加工时左侧顶叶楔前叶、左侧前额叶背外侧显著激活.结论汉字情景记忆时左右大脑半球激活区存在不对称性,fMRI可对此种功能皮层进行准确定位.     

正常老年人静息状态脑功能磁共振的默认网络研究

目的 探讨正常老年人静息状态下的功能磁共振(fMRI)默认网络结构及意义.方法 正常健康老年受试者18人,接受静息fMRI扫描;通过时程相关方法检测fMRI数据低频波动信号中以后扣带回为种子区的默认网络,经SPM2软件单样本t检验,激活脑区周值设为经校正的P<0.001,激活像素范围>5.结果 与后扣带回相关的静息状态网络连接的脑区有:前额叶内侧区、海马、颞极、颞中上回、丘脑枕部、楔叶及楔前叶、部分视皮层、顶下小叶.海马区和顶下小叶呈侧化性激活.结论 正常老年人存在基本完整的静息状态fMRI默认网络结构,其部分呈侧化性可能是与老年期脑功能重塑有关.     

功能磁共振观察反应抑制功能老化

目的 应用fMRI探讨反应抑制功能老化的神经功能特点。方法 对正常青年组及老年组（各25名）行停止信号任务fMRI扫描,使用SPM 8软件处理数据,以组间差异脑激活区作为反应抑制功能老化相关脑区,对各区信号强度与行为学数据 行相关性分析。结果 fMRI脑激活区（P<0.01,FDR校正）在青年组激活以额、顶叶为主,老年组激活区左侧化分布略明显;老年组较青年组在双侧前额中回、左侧额下回、右侧顶下小叶及尾状核头、前扣带回有强激活区。相关性分析显示,青年组右侧前额中回与SSRT呈正相关,左侧额中回、左侧额中/下回与SSRT呈负相关;老年组前扣带回、左侧额中回、左侧额中/下回与SSRT均呈正相关。结论 老年人反应抑制功能老化,依赖更多脑区进行功能代偿,主要依赖左侧额中/下回进行补充代偿和前扣带回进行重建代偿。     

功能磁共振成像观察2型糖尿病患者工作记忆

目的 通过功能磁共振成像技术对2型糖尿病患者的工作记忆进行研究,探讨2型糖尿病患者工作记忆的受损状况.方法 采用1-back组块设计,对16例2型糖尿病患者及13名正常对照受试者,进行词语及客体工作记忆任务的fMRI检查,对反应时间、正确率及脑激活图进行分析.结果 2型糖尿病组患者的正确反应时间、正确率与对照组相比差异无统计学意义(P>0.05).与对照组相比,2型糖尿病组在词语工作记忆时,左侧额叶、左侧顶叶及海马旁回等脑区激活显著减弱(P<0.05),客体工作记忆时,右侧额叶、左侧顶叶及双侧枕叶等脑区激活减弱(P<0.05).结论 2型糖尿病患者存在词语及客体工作记忆损害,经典激活脑区存在损害.     

线索诱发海洛因渴求的功能磁共振成像研究

目的识别与线索诱发海洛因渴求相关的特异脑区的神经网络活动。方法采用病例对照研究。选取海洛因依赖者和健康对照者各10人,在观看自然风光和海洛因相关录像时进行全脑磁共振(MRI)扫描。比较:①不同受试组观看海洛因相关录像时激活脑区的差异,②海洛因依赖者观看自然风光和海洛因相关录像时激活脑区的差异。应用功能性神经图像分析(AFNI)软件包进行数据分析。结果①观看海洛因相关录像时,海洛因依赖者与健康对照者相比左前额叶皮层激活最为明显。②海洛因依赖者观看海洛因相关录像与观看自然风光录像比较发现,左前扣带回、左额叶内侧回(BA10)、小脑山顶,中脑导水管旁灰质,以及右侧前楔叶可见显著激活。结论线索诱发海洛因渴求的特异激活脑区集中在左前扣带回和左前额叶皮层。中脑导水管旁灰质可能参与渴求的产生与维持。     

Brain activations during visual search: contributions of search efficiency versus feature binding

We investigated the involvement of the parietal cortex in binding features during visual search using functional magnetic resonance imaging. We tested 10 subjects in four visual search tasks across which we independently manipulated (1) the requirement to integrate different types of features in a stimulus (feature or conjunction search) and (2) the degree of search efficiency (efficient or inefficient). We identified brain areas that were common to all conditions of visual search and areas that were sensitive to the factors of efficiency and feature binding. Visual search engaged an extensive network of parietal, frontal, and occipital areas. The factor of efficiency exerted a strong influence on parietal activations along the intraparietal sulcus and in the superior parietal lobule. These regions showed a main effect of efficiency and showed a simple effect when inefficient conditions were compared directly with efficient pop-out conditions in the absence of feature binding. Furthermore, a correlation analysis supported a tight correspondence between posterior parietal activation and the slope of reaction-time search functions. Conversely, feature binding during efficient pop-out search was not sufficient to modulate the parietal cortex. The results confirm the important role of the parietal cortex in visual search, but suggest that feature binding is not a requirement to engage its contribution.     

Neuroanatomic overlap of working memory and spatial attention networks: a functional MRI comparison within subjects

Frontal and posterior parietal activations have been reported in numerous studies of working memory and visuospatial attention. To directly compare the brain regions engaged by these two cognitive functions, the same set of subjects consecutively participated in tasks of working memory and spatial attention while undergoing functional MRI (fMRI). The working memory task required the subject to maintain an on-line representation of foveally displayed letters against a background of distracters. The spatial attention task required the subject to shift visual attention covertly in response to a centrally presented directional cue. The spatial attention task had no working memory requirement, and the working memory task had no covert spatial attention requirement. Subjects' ability to maintain central fixation was confirmed outside the MRI scanner using infrared oculography. According to cognitive conjunction analysis, the set of activations common to both tasks included the intraparietal sulcus, ventral precentral sulcus, supplementary motor area, frontal eye fields, thalamus, cerebellum, left temporal neocortex, and right insula. Double-subtraction analyses yielded additional activations attributable to verbal working memory in premotor cortex, left inferior prefrontal cortex, right inferior parietal lobule, precuneus, and right cerebellum. Additional activations attributable to covert spatial attention included the occipitotemporal junction and extrastriate cortex. The use of two different tasks in the same set of subjects allowed us to provide an unequivocal demonstration that the neural networks subserving spatial attention and working memory intersect at several frontoparietal sites. These findings support the view that major cognitive domains are represented by partially overlapping large-scale neural networks. The presence of this overlap also suggests that spatial attention and working memory share common cognitive features related to the dynamic shifting of attentional resources.     

In search of the hidden: an fMRI study with implications for the study of patients with autism and with acquired brain injury

The Embedded Figures Task involves a search for a target hidden in a more complex visual pattern. The task has been used to study local perception and visual search in a range of normal and pathological populations. After acquired brain damage, impairment on embedded figures is strongly associated with aphasia; in the context of developmental disorder, people with autism or with Asperger's syndrome are reliably found to be better than normal controls on the task. The current study employed functional MRI with healthy volunteers to elucidate the brain regions that are specifically involved in the local search aspects of the Embedded Figures Task. We did so by analyzing the neural activations that are implicated in the task over and above those involved in an easier visual search task and in a straightforward shape recognition task. Significant activations (P < 0.05, corrected) specific in the above sense to the Embedded Figures Task were found in left inferior and left superior parietal cortex and in left ventral premotor cortex (inferior frontal gyrus). By contrast, comparing the overall effect of visual search within geometric figures to pure recognition of geometric shapes revealed more widespread activations in parietal, occipital, cerebellar, and frontal areas bilaterally. The implications of these findings for some developmental and acquired pathologies of perceptual functioning are outlined. We also relate our results to studies of local/global processing in other tasks.     

The large-scale neural network for spatial attention displays multifunctional overlap but differential asymmetry

Functional magnetic resonance imaging (fMRI) was used to determine the brain regions activated by two types of covert visuospatial attentional shifts: one based on exogenous spatial priming and the other on foveally presented cues which endogenously regulated the direction of spatial expectancy. Activations were seen in the cortical and subcortical components of a previously characterized attentional network, namely, the frontal eye fields, posterior parietal cortex, the cingulate gyrus, the putamen, and the thalamus. Additional activations occurred in the anterior insula, dorsolateral prefrontal cortex, temporo-occipital cortex in the middle and inferior temporal gyri, the supplementary motor area, and the cerebellum. Direct comparisons showed a nearly complete overlap in the location of activations resulting from the two tasks. However, the spatial priming task displayed a more pronounced rightward asymmetry of parietal activation, and a conjunction analysis showed that the area of posterior parietal cortex jointly activated by both tasks was more extensive in the right hemisphere. Furthermore, the posterior parietal and temporo-occipital activations were more pronounced in the task of endogenous attentional shifts. The results show that both exogenous (based on spatial priming) and endogenous (based on expectancy cueing) shifts of attention are subserved by a common network of cortical and subcortical regions. However, the differences between the two tasks, especially in the degree of rightward asymmetry, suggests that the pattern of activation within this network may show variations that reflect the specific attributes of the attentional task.     

Frontoparietal mechanisms supporting attention to location and intensity of painful stimuli

Attention can profoundly shape the experience of pain. However, little is known about the neural mechanisms that support directed attention to nociceptive information. In the present study, subjects were cued to attend to either the spatial location or the intensity of sequentially presented pairs of painful heat stimuli during a delayed match-to-sample discrimination task. We hypothesized that attention-related brain activation would be initiated after the presentation of the attentional cue and would be sustained through the discrimination task. Conjunction analysis confirmed that bilateral portions of the posterior parietal cortex (intraparietal sulcus [IPS] and superior parietal lobule) exhibited this sustained activity during attention to spatial but not intensity features of pain. Analyses contrasting activation during spatial and intensity attention tasks revealed that the right IPS region of the posterior parietal cortex was consistently more activated across multiple phases of the spatial task. However, attention to either feature of the noxious stimulus was associated with activation of frontoparietal areas (IPS and frontal eye fields) as well as priming of the primary somatosensory cortex. Taken together, these results delineate the neural substrates that support selective amplification of different features of noxious stimuli for utilization in discriminative processes.     

Mathematically gifted adolescents use more extensive and more bilateral areas of the fronto-parietal network than controls during executive functioning and fluid reasoning tasks

The main goal of this study was to investigate the neural substrates of fluid reasoning and visuospatial working memory in adolescents with precocious mathematical ability. The study population comprised two groups of adolescents: 13 math-gifted adolescents and 14 controls with average mathematical skills. Patterns of activation specific to reasoning tasks in math-gifted subjects were examined using functional magnetic resonance images acquired while the subjects were performing Raven's Advanced Progressive Matrices (RAPM) and the Tower of London (TOL) tasks. During the tasks, both groups showed significant activations in the frontoparietal network. In the math-gifted group, clusters of activation were always bilateral and more regions were recruited, especially in the right hemisphere. In the TOL task, math-gifted adolescents showed significant hyper-activations relative to controls in the precuneus, superior occipital lobe (BA 19), and medial temporal lobe (BA 39). The maximum differences between the groups were detected during RAPM tasks at the highest level of difficulty, where math-gifted subjects showed significant activations relative to controls in the right inferior parietal lobule (BA 40), anterior cingulated gyrus (BA 32), and frontal (BA 9, and BA 6) areas. Our results support the hypothesis that greater ability for complex mathematical reasoning may be related to more bilateral patterns of activation and that increased activation in the parietal and frontal regions of math-gifted adolescents is associated with enhanced skills in visuospatial processing and logical reasoning.     

Distinct anatomy for visual search and bisection: a neuroimaging study

Individuals with spatial neglect following brain injury often show biased performance on landmark bisection tasks (judging if a single item is transected at its midpoint) and search tasks (where they seek target(s) from an array of items). Interestingly, it appears that bisection deficits dissociate from other measures of neglect (including search tasks), and neglect patients with bisection deficits typically have more posterior injury than those without these symptoms. While previous studies in healthy adults have examined each of these tasks independently, our aim was to directly contrast brain activity between these two tasks. Our design used displays that were interpreted as landmark bisection stimuli in some blocks of trials and as search arrays on other trials. Therefore, we used a design where low-level perceptual and motor responses were identical across tasks. Both tasks generated significant activity in bilateral midfusiform gyrus, largely right lateralized activity in the posterior parietal cortex, left lateralized activity in the left motor cortex (consistent with right handed response) and generally right lateralized insular activation. Several brain areas showed task-selective activations when the two tasks were directly compared. Specifically, the superior parietal cortex was selectively activated during the landmark task. On the other hand, the search task caused stronger bilateral activation in the anterior insula, along with midfusiform gyrus, medial superior frontal areas, thalamus and right putamen. This work demonstrates that healthy adults show an anatomical dissociation for visual search and bisection behavior similar to that reported in neurological patients, and provides coordinates for future brain stimulation studies.     

生物类与非生物类图片命名任务对大脑活动时空模式的影响

目的：探讨图片的语义类别对命名任务的影响，研究生物类和非生物类图片命名任务对正常大脑活动时空模式的影响。方法：入组健康成年右利手受试者10例，选取来自不同语义类别（生物类和非生物类）的图片20张，应用磁共振成像获取个体大脑结构，脑磁图（MEG）检测任务中的全脑活动。结果：在图片命名任务中，早期脑区激活从双侧枕叶开始，逐步向颞叶和顶叶扩散，最后额叶激活产生言语。在视觉相关时间窗内，生物类图片命名在右侧扣带回激活强度显著低于非生物类图片命名（P=0.0475），而生物类图片命名在双侧枕叶、左侧顶叶和左侧额叶均显著高于非生物类图片命名（均P＜0.05）。在语义相关时间窗内，生物类图片命名在双侧额叶显著高于非生物类图片命名（P＜0.05）。在语音相关时间窗内，生物类图片命名在双侧枕叶、左侧顶叶和左侧额叶均显著高于非生物类图片命名（均P＜0.05）。结论：生物类和非生物类图片命名相比，两者在颞叶的活动未见显著差异，但前者具有枕叶、顶叶和额叶优势激活。提示生物类图片可以更好地在相关时间窗内刺激相关功能脑区。     

轻度认知障碍患者记忆力的功能磁共振研究

目的为探索早期诊断阿尔茨海默病 (AD)的方法 ,将神经心理测定和功能磁共振 (fMRI)检查相结合 ,了解轻度认知障碍 (MCI)患者在记忆方面的脑功能情况。方法 9例MCI患者和 9名正常对照在进行无意义图形记忆和再认时行fMRI检查 ,对反应时间、正确率和fMRI的脑激活图进行比较。结果患者的反应时间比正常对照明显延长 (P <0 0 1) ,正确率显著降低 (P <0 0 0 1)。脑激活图显示 ,与对照相比 ,在记忆编码时 ,患者主要在左侧前额叶背外侧和海马旁回、以及以右侧为主的后部脑区激活减弱 ,记忆提取时 ,在双侧前额叶背外侧 ,左侧海马旁回和前扣带回 ,以及后部脑区激活减弱。结论MCI患者的记忆功能已有损害。记忆功能的fMRI检查与认知神经心理学的联合研究能为早期诊断AD提供有力的参考依据。     

Effects of word form on brain processing of written Chinese

Both logographic characters and alphabetic pinyins can be used to write words in Chinese. Here we use fMRI to address the question of whether the written form affects brain processing of a word. Fifteen healthy, right-handed, native Chinese-reading volunteers participated in our study and were asked to read silently either Chinese characters (8 subjects) or pinyins (7 subjects). The stimulus presentation rate was varied for both tasks to allow us to identify brain regions with word-load-dependent activation. Rate effects (fast minus slow presentations) for Chinese character reading were observed in striate and extrastriate visual cortex, superior parietal lobule, left posterior middle temporal gyrus, bilateral inferior temporal gyri, and bilateral superior frontal gyri. Rate effects for pinyin reading were observed in bilateral fusiform, lingual, and middle occipital gyri, bilateral superior parietal lobule/precuneus, left inferior parietal lobule, bilateral inferior temporal gyrus, left middle temporal gyrus, and left superior temporal gyrus. These results demonstrate that common regions of the brain are involved in reading both Chinese characters and pinyins, activated apparently independently of the surface form of the word. There also appear to be brain regions in which activation is dependent on word form. However, it is unlikely that these are entirely specific for a given word form; their activation more likely reflects relative functional specializations within broader networks for processing written language.