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.     

2型糖尿病患者工作记忆相关脑区的无效率激活

目的：探讨2型糖尿病（T2DM）患者工作记忆相关脑区的激活改变,及其可能的神经机制。方法：对21例T2DM患者及21名正常对照受试者进行数字1-back任务下的fMRI实验。采用SPM8软件进行数据预处理和统计分析,组内分析采用单样本t检验,组间比较采用双样本t检验,统计阈值均设定为P<0.01（AlphaSim校正）。将组间差异区的BOLD信号变化百分比与工作记忆任务的反应时间及糖化血红蛋白之间进行相关分析。结果：T2DM组的空腹血糖和糖化血红蛋白明显高于对照组（P<0.001）,1-back任务的正确率明显低于对照组（P<0.05）。在1-back任务下,T2DM组的双侧前额叶腹外侧及背外侧、右侧后顶叶皮层的激活强度明显高于对照组（P<0.01）,左侧顶下小叶和右侧额上回的负激活程度明显低于对照组（P<0.01）。双侧前额皮层背外侧的激活强度与1-back任务的反应时间明显负相关（P<0.05）。结论：T2DM患者存在工作记忆能力损害,工作记忆相关脑区以过度激活的模式对工作记忆能力进行有限的代偿。     

精神分裂症患者工作记忆不同认知成分的fMRI研究

目的：采用事件相关功能磁共振成像（ER-fMRI）探讨精神分裂症患者与正常对照组执行工作记忆不同认知成分即编码、维持和提取过程的神经机制差别。方法：使用fMRI技术,观察16名正常受试者和20名精神分裂症患者在执行Sternberg项目认知任务（SIRT）的编码、维持和提取过程时的激活脑区。结果：与正常组比较,患者组工作记忆不同认知过程的执行脑区激活程度增加,编码期激活增加脑区为右侧楔前叶,维持期激活增加脑区为左侧PMA、左侧DLPFC、右侧楔前叶及左侧VLPFC,提取期激活增加脑区为左侧PMA,而且患者组还激活了更多皮层下结构、初级运动皮层及左侧颞叶语言相关脑区。结论：精神分裂症患者工作记忆编码、维持和提取成分的一些执行脑区皮层效率功能低下。     

注意缺陷多动障碍儿童小脑功能缺陷的功能磁共振成像

目的 初步观察注意缺陷多动障碍(ADHD)儿童在执行工作记忆任务时小脑和其他脑区激活有无异常.方法 以12例ADHD儿童和12名年龄、性别、利手、受教育程度方面相匹配的正常对照为研究对象,通过运用快速事件相关fMRI及分类n-back工作记忆任务,研究ADHD儿童小脑等主要脑区激活有无改变.结果 ADHD儿童左侧小脑后叶激活较正常对照明显减弱(P<0.01).结论 ADHD儿童在执行n-back工作记忆任务时显示左侧小脑后叶功能低下.小脑功能低下及其所在的高级认知神经回路功能障碍,可能是ADHD儿童行为学异常的神经基础所在.     

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。     

精神分裂症患者任务诱发去激活的fMRI研究

目的：任务诱发去激活（Task induced deactivation,TID）皮层区是静息态脑功能的“默认”模式相关脑区,可能与自我定向思维活动有关。本文探讨精神分裂症患者中线TID脑区是否出现变化,以及TID脑区与患者情感状态、行为学表现间的相关性。材料与方法：15例精神分裂症患者和15例与之匹配的正常对照组执行2-back工作记忆任务时行全脑BOLD-fMRI扫描,对每个受试者进行PANAS量表评定。结果：与正常组比较,患者组2-back任务中反应时间（RT）延长,前额叶内侧皮层（MPFC）、后内侧皮层（PMC）脑区TID效应降低,负性情绪评分增加;患者组MPFC区TID与RT、负性情绪评分呈负相关。结论：精神分裂症患者在认知任务执行中存在着认知-情感之间注意资源转移效率障碍,这可能是精神分裂症患者认知功能障碍的神经机制之一。     

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。     

左侧颞叶癫痫患者脑皮质计算功能重组的fMRI研究

目的采用任务相关功能性磁共振成像技术（fMRI）观察左侧颞叶癫痫（TLE）患者与健康人完成计算任务时脑区激活差异。 方法选取右利手、左侧TLE患者16例作为TLE组,另选取相匹配健康受试者16例作为对照组。2组受试者均进行简单加法、简单减法及退位减法计算任务,同时进行脑部fMRI检查。采用神经影像学统计参数图（SPM-5）软件进行数据处理和分析,并比较2组间脑区激活差异。 结果计算任务中,TLE组的计算正确率为76.30%,显著低于对照组的96.80%（P<0.05）;而TLE患者组的计算反应时间为（2589±213.20）ms,与对照组的（1765±134.90）ms比较,差异有统计学意义（P<0.05）。对照组激活强度高于左侧颞叶癫痫组的脑区有左侧中央旁小叶、左侧中央后回、双侧顶下小叶、左侧角回、双侧缘上回、左侧额中回、左额上回、双侧后扣带回、双侧岛叶、双侧颞上下回、右侧海马、海马旁回、双侧丘脑和小脑。左侧颞叶癫痫组激活强度高于对照组的脑区有双侧顶上小叶、双侧前扣带回和右侧额中下回。 结论左侧TLE患者计算相关的脑功能区具有半球内及半球间重组,额顶叶可在计算功能的代偿中发挥一定的作用;任务相关fMRI技术可为无创评价TLE患者计算认知功能提供重要证据。     

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.     

一体化PET/MRI评估帕金森病患者脑葡萄糖代谢与局部一致性的关系

目的 采用一体化¹⁸F-FDG-PET/MRI观察帕金森病(PD)患者脑葡萄糖代谢与局部一致性(ReHo)的关系。方法 前瞻性纳入34例PD患者(PD组)及25名健康受试者(对照组),行颅脑一体化PET/MR检查；以独立样本t检验比较组间脑葡糖代谢标准摄取值比值(SUVR)及ReHo差异，通过Pearson相关性分析探讨SUVR与ReHo异常重叠脑区二者的关系，以及PD患者重叠脑区SUVR、ReHo与病程及临床量表评分的相关性。结果 相比对照组，PD组初级感觉运动区、中央旁小叶、壳核、苍白球及丘脑SUVR升高(P均<0.05,经FDR校正),视觉区、颞叶及顶叶SUVR降低(P均<0.05,经FDR校正);视觉区、颞叶及顶叶ReHo升高(P均<0.05,经FDR校正),中央旁小叶、壳核、苍白球、丘脑、脑干、额下回眶部及后扣带回ReHo降低(P均<0.05,经FDR校正)。SUVR与ReHo异常重叠脑区包括双侧颞下回、双侧枕中回、双侧壳核、双侧中央旁小叶及左侧距状裂；上述区域中，SUVR与ReHo组间差异有显著空间相似性(r=-0.84,P=0...     

Prolonged reaction time to a verbal working memory task predicts increased power of posterior parietal cortical activation

We used multislice functional magnetic resonance imaging (fMRI) to investigate the association between behavioral and neurophysiological measures of working memory task performance in 20 right-handed male healthy volunteers. Images were acquired over a 5-min period at 1.5 Tesla. We used a periodic design, alternating 30-s blocks of the "n-back" working memory task with 30-s blocks of a sensorimotor control task to activate verbal working memory systems. The power of functional response to the task was estimated by sinusoidal regression at each voxel. The relationship between power of fMRI response and mean reaction time over all 11 working memory trials was explored by multiple regression, with age and mean reaction time to the control task as covariates, at voxel and regional levels of analysis. All subjects were able to perform the n-back task accurately. A spatially distributed network was activated, including dorsolateral prefrontal cortex, inferior frontal gyrus, lateral premotor cortex, and supplementary motor area (SMA) in the frontal lobes. More posteriorly, there were major foci of activation in parietal and occipitoparietal cortex, precuneus, lingual, and fusiform gyri of the ventral occipital lobe, inferior temporal gyrus, and cerebellum. The power of functional response was positively correlated with reaction time in bilateral posterior parietal cortex (Talairach coordinates in x, y, z (mm) 35, -44, 37 and -32, -56, 42), indicating that subjects who found the task difficult, and responded with a slower reaction time, tended to activate these regions more powerfully. One interpretation of this regionally specific relationship between prolonged reaction time and increased power of posterior parietal activation is consistent with prior studies identifying similar areas of parietal cortex as the site of the phonological storage function in verbal working memory.     

Developmental neural networks in children performing a Categorical N-Back Task

The prefrontal and temporal networks subserving object working memory tasks in adults have been reported as immature in young children; yet children are adequately capable of performing such tasks. We investigated the basis of this apparent contradiction using a complex object working memory task, a Categorical n-back (CN-BT). We examined whether the neural networks engaged by the CN-BT in children consist of the same brain regions as those in adults, but with a different magnitude of activation, or whether the networks are qualitatively different. Event-related fMRI was used to study differences in brain activation between healthy children ages 6 and 10 years, and young adults (20-28 years). Performance accuracy and RTs in 10-year-olds and adults were comparable, but the performance in 6-year-olds was lower. In adults, the CN-BT was highly effective in engaging the bilateral (L>R) ventral prefrontal cortex, the bilateral fusiform gyrus, posterior cingulate and precuneus, thus suggesting an involvement of the ventral visual stream, with related feature extraction and semantic labeling strategies. In children, the brain networks were distinctly different. They involved the premotor and parietal cortex, anterior insula, caudate/putamen, and the cerebellum, thus suggesting a predominant involvement of the visual dorsal and sensory-motor pathways, with related visual-spatial and action cognitive strategies. The findings indicate engagement of developmental networks in children reflecting task-effective brain activation. The age-related pattern of fMRI activation suggests a working hypothesis of a developmental shift from reliance on the dorsal visual stream and premotor/striatal/cerebellar networks in young children to reliance on the ventral prefrontal and inferior temporal networks in adults.     

Cognitive control and brain resources in major depression: an fMRI study using the n-back task

Several neuroimaging studies have reported 'hypofrontality' in depressed patients performing a cognitive challenge compared to control subjects. Hypofrontality in depression is likely associated with an impaired behavioral performance. It is unclear whether this impaired performance is the consequence or the cause of hypofrontality. Consequently, we proposed to compare the cerebral activity of depressed patients and healthy subjects while controlling for the level of performance. Ten individuals meeting DSM-IV criteria for Major Depression and 10 healthy controls were tested with a verbal version of the n-back task during fMRI scanning. The working memory load was manipulated across the experiment (1,2,3-back) to increase the cognitive demands. fMRI data were acquired on a 1.5-T GE scanner and analyzed using SPM99 software. We did not find any difference between groups in both performance and reaction times for each level of complexity of the n-back task. Depressed patients and control subjects showed bilateral activation of the lateral prefrontal cortex, anterior cingulate and parietal cortex. Activation of these regions was modulated by the complexity of the task. Within this n-back neural network, depressed patients showed greater activation of the lateral prefrontal cortex and the anterior cingulate compared to healthy subjects. This study provides evidence that depressed patients need greater activation within the same neural network to maintain a similar level of performance as controls during a working memory task. Our findings suggest that depression may impair the cognitive capacity of depressed patients by recruiting more brain resources than controls during cognitive control.     

Functional MRI BOLD response to Tower of London performance of first-episode schizophrenia patients using cortical pattern matching

Due to its three-dimensional folding pattern, the human neocortex poses a challenge for accurate co-registration of grouped functional brain imaging data. The present study addressed this problem by employing three-dimensional continuum-mechanical image-warping techniques to derive average anatomical representations for co-registration of functional magnetic resonance brain imaging data obtained from 10 male first-episode schizophrenia patients and 10 age-matched male healthy volunteers while they performed a version of the Tower of London task. This novel technique produced an equivalent representation of blood oxygenation level dependent (BOLD) response across hemispheres, cortical regions, and groups, respectively, when compared to intensity average co-registration, using a deformable Brodmann area atlas as anatomical reference. Somewhat closer association of Brodmann area boundaries with primary visual and auditory areas was evident using the gyral pattern average model. Statistically-thresholded BOLD cluster data confirmed predominantly bilateral prefrontal and parietal, right frontal and dorsolateral prefrontal, and left occipital activation in healthy subjects, while patients' hemispheric dominance pattern was diminished or reversed, particularly decreasing cortical BOLD response with increasing task difficulty in the right superior temporal gyrus. Reduced regional gray matter thickness correlated with reduced left-hemispheric prefrontal/frontal and bilateral parietal BOLD activation in patients. This is the first study demonstrating that reduction of regional gray matter in first-episode schizophrenia patients is associated with impaired brain function when performing the Tower of London task, and supports previous findings of impaired executive attention and working memory in schizophrenia.     

Genetic variation in the schizophrenia-risk gene neuregulin1 correlates with differences in frontal brain activation in a working memory task in healthy individuals

Working memory dysfunctions are a prominent feature in schizophrenia. These impairments have been linked to alterations in prefrontal brain activation with studies reporting hypo- and hyperactivations. Since schizophrenia has a high heritability, it is of interest whether susceptibility genes modulate working memory and its neural correlates. The aim of the present study was to test the influence of the NRG1 schizophrenia susceptibility gene on working memory and its neural correlates in healthy subjects. 429 healthy individuals performed a verbal and a spatial working memory task. A subsample of 85 subjects performed a 2-back version of the Continuous Performance Test (CPT) in a functional MRI study. The NRG1 SNP8NRG221533 (rs35753505) carrier status was determined and correlated with working memory performance and brain activation.There were no effects of genetic status on behavioural performance in the working memory tasks in the 429 subjects and in the fMRI task (n = 85). A linear effect of NRG1 SNP8NRG221533 carrier status on neuronal activation emerged in the fMRI experiment. Hyperactivation of the superior frontal gyrus (BA 10) was correlated with the number of risk alleles. The fMRI data suggest that performance measures between groups did not differ due to a compensational activation of BA 10 in risk-allele carriers. Our results are in line with functional imaging studies in patients with schizophrenia, which also showed a differential activation in lateral prefrontal areas.     

A longitudinal fMRI study of working memory in severe TBI patients with diffuse axonal injury

Traumatic brain injury (TBI) patients have working memory deficits and altered patterns of brain activation during this function. The evolution of the impairment has not been examined to date. This study investigated longitudinal changes in brain activation during a working memory task. Twelve patients with severe and diffuse TBI and ten healthy matched controls were fMRI scanned twice at a 6-month interval during an n-back task (0-, 2- and 3-back). All the TBI patients selected presented signs of diffuse axonal injury on CT but had no evidence of focal lesions on MRI clinical examination. Significant changes in brain activation over time were observed in patients, but not in controls. During the first examination, though both groups engaged bilateral fronto-parietal regions known to be involved in working memory, activation of the right superior frontal gyrus was low in the TBI group. However, the difference between TBI and controls had decreased significantly after 6 months. A factor analysis confirmed the greater increase in activation in the right superior frontal cortex in the TBI group than in healthy controls, leading to normalization of the brain activation pattern. In conclusion, this longitudinal study provides evidence of a progressive normalization of the working memory activation pattern after diffuse axonal injury in severe TBI, coinciding with an improvement in performance on this function.     

Males and females differ in brain activation during cognitive tasks

To examine the effect of gender on regional brain activity, we utilized functional magnetic resonance imaging (fMRI) during a motor task and three cognitive tasks; a word generation task, a spatial attention task, and a working memory task in healthy male (n = 23) and female (n = 10) volunteers. Functional data were examined for group differences both in the number of pixels activated, and the blood-oxygen-level-dependent (BOLD) magnitude during each task. Males had a significantly greater mean activation than females in the working memory task with a greater number of pixels being activated in the right superior parietal gyrus and right inferior occipital gyrus, and a greater BOLD magnitude occurring in the left inferior parietal lobe. However, despite these fMRI changes, there were no significant differences between males and females on cognitive performance of the task. In contrast, in the spatial attention task, men performed better at this task than women, but there were no significant functional differences between the two groups. In the word generation task, there were no external measures of performance, but in the functional measurements, males had a significantly greater mean activation than females, where males had a significantly greater BOLD signal magnitude in the left and right dorsolateral prefrontal cortex, the right inferior parietal lobe, and the cingulate. In neither of the motor tasks (right or left hand) did males and females perform differently. Our fMRI findings during the motor tasks were a greater mean BOLD signal magnitude in males in the right hand motor task, compared to females where males had an increased BOLD signal magnitude in the right inferior parietal gyrus and in the left inferior frontal gyrus. In conclusion, these results demonstrate differential patterns of activation in males and females during a variety of cognitive tasks, even though performance in these tasks may not vary, and also that variability in performance may not be reflected in differences in brain activation. These results suggest that in functional imaging studies in clinical populations it may be sensible to examine each sex independently until this effect is more fully understood.     

Comparison of fMRI activation at 3 and 1.5 T during perceptual,cognitive, and affective processing

Previous studies comparing fMRI data acquired at 1.5 T and higher field strengths have focused on examining signal increases in the visual and motor cortices. No information is, however, available on the relative gain, or the comparability of data, obtained at higher field strengths for other brain regions such as the prefrontal and other association cortices. In the present study, we investigated fMRI activation at 1.5 and 3 T during visual perception, visuospatial working memory, and affect-processing tasks. A 23% increase in striate and extrastriate activation volume was observed at 3 T compared with that for 1.5 T during the visual perception task. During the working memory task significant increases in activation volume were observed in frontal and parietal association cortices as well as subcortical structures, including the caudate, globus pallidus, putamen, and thalamus. Increases in working memory-related activation volume of 82, 73, 83, and 36% were observed in the left frontal, right frontal, left parietal, and right parietal lobes, respectively, for 3 T compared with 1.5 T. These increases were characterized by increased activation at 3 T in several prefrontal and parietal cortex regions that showed activation at 1.5 T. More importantly, at 3 T, activation was detected in several regions, such as the ventral aspects of the inferior frontal gyrus, orbitofrontal gyrus, and lingual gyrus, which did not show significant activation at 1.5 T. No difference in height or extent of activation was detected between the two scanners in the amygdala during affect processing. Signal dropout in the amygdala from susceptibility artifact was greater at 3 T, with a 12% dropout at 3 T compared with a 9% dropout at 1.5 T. The spatial smoothness of T2* images was greater at 3 T by less than 1 mm, suggesting that the greater extent of activation at 3 T beyond these spatial scales was not due primarily to increased intrinsic spatial correlations at 3 T. Rather, the increase in percentage of voxels activated reflects increased sensitivity for detection of brain activation at higher field strength. In summary, our findings suggest that functional imaging of prefrontal and other association cortices can benefit significantly from higher magnetic field strength.     

Functional neuroanatomy of auditory working memory in schizophrenia: relation to positive and negative symptoms

Functional brain imaging studies of working memory (WM) in schizophrenia have yielded inconsistent results regarding deficits in the dorsolateral prefrontal (DLPFC) and parietal cortices. In spite of its potential importance in schizophrenia, there have been few investigations of WM deficits using auditory stimuli and no functional imaging studies have attempted to relate brain activation during auditory WM to positive and negative symptoms of schizophrenia. We used a two-back auditory WM paradigm in a functional MRI study of men with schizophrenia (N = 11) and controls (N = 13). Region of interest analysis was used to investigate group differences in activation as well as correlations with symptom scores from the Brief Psychiatric Rating Scale. Patients with schizophrenia performed significantly worse and were slower than control subjects in the WM task. Patients also showed decreased lateralization of activation and significant WM related activation deficits in the left and right DLPFC, frontal operculum, inferior parietal, and superior parietal cortex but not in the anterior cingulate or superior temporal gyrus. These results indicate that in addition to the prefrontal cortex, parietal cortex function is also disrupted during WM in schizophrenia. Withdrawal-retardation symptom scores were inversely correlated with frontal operculum activation. Thinking disturbance symptom scores were inversely correlated with right DLPFC activation. Our findings suggest an association between thinking disturbance symptoms, particularly unusual thought content, and disrupted WM processing in schizophrenia.