轻度认知障碍老年人情节记忆功能的磁共振成像研究

目的 运用核磁共振(MRI)技术探讨轻度认知障碍(MCI)老人与健康老人脑结构和功能的异同.方法 对14例MCI老人(MCI组)和15名健康老人(正常对照组)进行神经心理学检查,并应用基于体素的形态测量方法 ,测定两组的灰质体积,并用事件相关功能MRI技术,测定两组在执行情节记忆提取任务时相关脑区的功能变化.结果 (1)神经心理学:MCI组听觉词语记忆测试[(2.1±1.7)分]和画钟试验[(7.8±1.2)分]成绩差于正常对照组[分别为(9.2±1.3)分和(9.2±0.8)分;P＜0.05].(2)结构影像:MCI组的灰质体积小于正常对照组,主要位于情节记忆相关脑区(P＜0.001).(3)功能影像:MCI组与正常对照组任务正确率和反应时间的差别无统计学意义;MCI组激活降低的脑区主要是海马旁回,而增强激活的脑区主要是前额叶前侧、背外侧、右侧颞上回、右侧颞下回、枕叶皮层(P＜0.005).结论 MCI组内侧颞叶记忆系统结构萎缩、功能下降,在任务难度适当的情节记忆提取任务中,MCI组动员额外脑区激活,以代偿颞叶内侧记忆系统的损害.     

脑功能磁共振成像研究进展

主要综述fMRI产生的历史、成像原理、成像技术和方法、已经取得的成绩以及将来研究发展的方向等。fMRI产生技术广泛应用的20世纪90年代,主要受快速成像技术的影响,从有创走向无创,从而受到神经、认知和心理科学领域的极大关注。fMRI原理是根据神经元兴奋后局部氧耗与血流增幅不一致,而BOLD效应机制成像,间接显示神经元活动。成像主要采用平面回波成像（EPI）和快速小角度激发（FLASH）技术、二者在时间和空间分辨率上各有优劣。最后几年来,fMRI技术对脑功能的研究已取得了巨大的成绩,估计将在这一领域继续拥有非常重要的地位。将来fMRI可能主要在BOLD效应的生理过程、临床应用以及高场磁体的应用等领域进一步展开。     

功能磁共振成像与语言学研究

长期以来，语言作为一种人脑的高级皮质活动功能而备受研究关注。人们从多学科、多层次、水平展开研究，试图揭示这一人类所特有的复杂活动过程。磁共振成像是继CT后利用形态学诊断疾病的一项新技术。从20世纪70年代末应用于临床医学诊断以来，发展异常迅速。进入90年代后，功能磁共振成像技术(fMRI)开始出现，它把神经活动和高分辨率磁共振成像技术相结合，从而为实现从形态和功能上探索脑高级皮质活动提供了可能，是目前人们所掌握的无侵入、无创伤，     

脑肿瘤功能磁共振成像研究与应用

功能磁共振成像(fMRI)主要包括扩散加权成像(DWI)、扩散张量成像(DTI)、灌注成像(PWI)、血氧水平依赖性功能磁共振成像(BOLD-fMRI)以及磁共振波谱(MRS)分析。fMRI能够无创性地对脑功能     

书写痉挛脑功能磁共振成像研究

目的 应用脑功能磁共振成像（fMRI）技术,观察书写痉挛患者痉挛性书写脑功能区激活特点,探讨书写痉挛可能发病机制.方法 采用fMRI组块设计,分别获得10例书写痉挛患者和10名年龄、性别匹配健康对照组执行默写、手写、笔写任务时的平均脑功能激活图,同时通过一般线性分析法产生“笔写减手写”及“笔写减默写”的差异脑功能图.结果 书写痉挛患者进行书写任务时,受累手对侧基底节区,特别是壳核（激活体素个数864）,较健康对照组（激活体素个数54）显著激活;运动皮质（第一运动区、辅助运动区、运动前区）及同侧小脑较健康对照亦有明显激活;而进行手指写和默写任务时两组间差异并不明显;＂笔写减手写＂及＂笔写减默写＂差异脑功能图发现书写痉挛患者在除去手指写运动及语言处理相关影响后上述脑区仍有明显激活,健康对照组则皮质下结构激活消失,运动相关皮质激活亦明显减少.结论 书写痉挛患者执行笔写任务时上述脑区尤其皮质下结构异常激活与书写痉挛发生存在一定关联,基底节区及相应皮质-皮质下环路功能紊乱,可能在书写痉挛发病机制中起到重要作用.     

癫痫磁共振功能成像研究进展

实现对癫痫病灶更精确的功能定位 ,始终是癫痫病学最为关注的研究方向之一。为达到这一目的 ,临床上采用多种技术手段 ,如神经电生理、神经影像学和近 10来年发展起来的功能影像技术等。ＥＥＧ的问世对癫痫的诊断产生了划时代的影响 ,脑磁图 (ＭＥＧ)和偶极子 (ｄｉｐｏｌｅ)技术的应用使癫痫灶的定位水平不断提高 ,至今 ,皮层电极和深部电极仍然是术中判断癫痫灶位置不可缺少的检查方法 ;ＣＴ、ＭＲＩ为癫痫的病因诊断提供了直观、清晰的解剖形态学图像 ;正电子发射体层摄影术 (ＰＥＴ)、单光子发射计算机体层摄影术(ＳＰＥＣＴ)、磁共振血…     

精神分裂症功能磁共振成像研究近况

本文介绍功能磁共振成像在精神分裂症的脑功能定位和功能连接的研究近况。     

成功老龄与轻度认知功能损害老年患者脑功能磁共振成像对照研究

目的探讨成功老龄与轻度认知功能损害老年人执行认知任务时的脑功能差异。方法对10例成功老龄(成功老龄组)和9例轻度认知功能损害(MCI,MCI组)患者进行词汇流畅性作业(VFTs)的功能磁共振成像检查,比较两组的VFTs和脑激活结果。结果(1)成功老龄组平均激活强度(F=10.16)大于MCI组(F=7.86),差异有统计学意义(P<0.01)。两组间各脑区激活体积差异均有统计学意义(P<0.01)。(2)成功老龄组的脑激活呈一致优势侧偏[偏侧化指数(LIs)=0.46],左顶叶、前额叶(包括背外侧皮质)、扣带前回及双侧枕叶的激活明显。(3)MCI组的脑激活总体上无偏侧性(LIs=-0.12),除右前额叶外,脑激活普遍低下,枕叶无明显激活。结论成功老龄的脑功能明显优于MCI,左前额叶尤其是背外侧皮质可能是与此差异相关的主要脑区。     

抑郁症不同状态下的功能磁共振成像研究

对近年来抑郁症的功能磁共振成像研究作一综述。     

工作记忆与脑的功能磁共振成像

工作记忆是临时信息编码、保持和提取的过程 ,是学习记忆研究的热点之一。功能磁共振作为一种新型无损伤技术 ,为研究工作记忆提供了一个新的途径。本文对功能磁共振的原理、实验设计和目前工作记忆功能磁共振检查的研究进展进行综述。     

An fMRI study of loneliness in younger and older adults

Loneliness, the subjective experience of social isolation, may reflect, in part, underlying neural processing of social signals. Aging may exacerbate loneliness due to decreased social networks and increased social isolation, or it may reduce loneliness due to preferential attentional processing of positive information and increased interactions with emotionally close partners. Here, we conducted a functional magnetic resonance imaging (fMRI) study of loneliness in younger (N = 50, 26 female, M_age = 20.4) and older (N = 49, 30 female, M_age = 62.9) adults. Compared to younger adults, older adults were less lonely and dwelled longer on faces, regardless of valence. Previous studies in younger adults found that loneliness was negatively correlated with ventral striatal (VS) activation to pleasant social pictures of strangers yet positively correlated with VS activation to faces of close others. In the present study, we observed no association between loneliness and VS activation to social pictures of strangers in either age group. Further, unlike previous studies, we observed no association between social network size and amygdala activation to social stimuli. Additional research is needed to examine the effect of loneliness and social network size on neural processing of different dimensions of social stimuli.     

An fMRI investigation of memory encoding in PTSD: influence of symptom severity

Previous studies have shown memory deficits in Post-Traumatic Stress Disorder (PTSD) patients, as well as abnormal patterns of brain activity, especially when retrieving trauma-related information. This study extended previous findings by investigating the neural correlates of successful memory encoding of trauma-unrelated stimuli and their relationship with PTSD symptom severity. We used the subsequent memory paradigm, in the context of event-related functional magnetic resonance imaging, in 27 PTSD patients to identify the brain regions involved in the encoding of fearful and neutral faces. Symptom severity was assessed by the Clinically Administered PTSD Scale (CAPS) scores. It was found that memory performance was negatively correlated with CAPS scores. Furthermore, a negative correlation was observed between CAPS scores and ventral medial prefrontal cortex (vmPFC) activity elicited by the subsequently forgotten faces. Finally, symptom severity predicted the contribution of the amygdala to the successful encoding of fearful faces. These results confirm the roles of the vmPFC and the amygdala in PTSD and highlight the importance of taking into account individual differences when assessing the behavioural and neural correlates of the disorder.     

An fMRI study of the functional neuroanatomy of picture encoding in younger and older adults

Age-related changes in the neural mechanisms of picture encoding were investigated using functional magnetic resonance imaging (fMRI). Seven younger and seven older adults were studied while they were encoding pairs of concrete-related, concrete-unrelated, and abstract pictures. Functional (T2*-weighted) and anatomical (T1-weighted) images of the brain were obtained using a 1.5 T MRI scanner. The results in the younger adults showed that the left dorsal prefrontal cortex (PFC) was activated during associative learning of the concrete-unrelated or abstract pictures. The results also suggest that both ventral and dorsal visual pathways are involved in the encoding of abstract pictures, and that the right superior parietal lobule likely mediates spatial information of the abstract pictures. The older adults showed significant activation in the left dorsal PFC under concrete-unrelated and abstract conditions. However, the older adults failed to activate either the left ventral and right dorsal PFC under the concrete-unrelated condition, or the parietal areas under abstract condition. A direct comparison between the two age groups demonstrates that the older adults had a reduced activation in the bilateral parieto-temporo-occipital areas under abstract condition, and in the right temporo-occipital area extending to the fusiform gyrus under the concrete-unrelated condition. Finally, age difference was found in correlation between memory performance and amplitude of signal change in the parahippocampal gyrus and fusiform gyrus under the concrete-unrelated and abstract conditions. These changes in neural response likely underlie the age-related memory decline in relation to pictorial information.     

An fMRI study of finger tapping in children and adults

Functional brain imaging studies have characterized the neural bases of voluntary movement for finger tapping in adults, but equivalent information for children is lacking. When contrasted to adults, one would expect children to have relatively greater activation, reflecting compensation for an underdeveloped motor system combined with less experience in the execution of voluntary movement. To test this hypothesis, we acquired functional magnetic resonance imaging (fMRI) data on 17 healthy right‐handed children (7.48 ± 0.66 years) and 15 adults (24.9 ± 2.9 years) while they performed an irregularly paced finger‐tapping task in response to a visual cue (left‐ and right‐hand examined separately). Whole‐brain within‐group analyses revealed that finger tapping in either age group and for either hand activated contralateral SM1, SMA, ipsilateral anterior cerebellum, and occipital cortices. We used an ANOVA factorial design to test for main effects of Age Group (children vs adults), Hand (left vs. right), and their interactions. For main effects of Age Group, children showed relatively greater activity in left SM1 (extending into bilateral SMA), and, surprisingly, adults exhibited relatively greater activity in right pre‐SMA/SMA (extending into left pre‐SMA/SMA), right lateral globus pallidus, left putamen, and right anterior cerebellum. The interaction of Age Group × Hand revealed that while both groups activated right SM1 during left finger tapping and exhibited signal decreases (i.e., below fixation baseline) during right finger tapping, both these responses were attenuated in children relative to adults. These data provide an important foundation by which to study children with motor disorders.     

Diffusion abnormalities in adolescents and young adults with a history of heavy cannabis use

Background

There is growing evidence that adolescence is a key period for neuronal maturation. Despite the high prevalence of marijuana use among adolescents and young adults in the United States and internationally, very little is known about its impact on the developing brain. Based on neuroimaging literature on normal brain developmental during adolescence, we hypothesized that individuals with heavy cannabis use (HCU) would have brain structure abnormalities in similar brain regions that undergo development during late adolescence, particularly the fronto-temporal connection.

Method

Fourteen young adult males in residential treatment for cannabis dependence and 14 age-matched healthy male control subjects were recruited. Patients had a history of HCU throughout adolescence; 5 had concurrent alcohol abuse. Subjects underwent structural and diffusion tensor magnetic resonance imaging. White matter integrity was compared between subject groups using voxelwise and fiber tractography analysis.

Results

Voxelwise and tractography analyses revealed that adolescents with HCU had reduced fractional anisotropy, increased radial diffusivity, and increased trace in the homologous areas known to be involved in ongoing development during late adolescence, particularly in the fronto-temporal connection via arcuate fasciculus.

Conclusions

Our results support the hypothesis that heavy cannabis use during adolescence may affect the trajectory of normal brain maturation. Due to concurrent alcohol consumption in five HCU subjects, conclusions from this study should be considered preliminary, as the DTI findings reported here may be reflective of the combination of alcohol and marijuana use. Further research in larger samples, longitudinal in nature, and controlling for alcohol consumption is needed to better understand the pathophysiology of the effect of cannabis on the developing brain.     

White matter hyperintensities in healthy older adults: A longitudinal study

A 3-year longitudinal study was conducted using magnetic resonance imaging (MRI) to determine the progression of white matter hyperintensities (WMH) and ventricle-to-brain ratio (VBR) in 16 healthy older adults. We found that, as a group, the subjects' WMH showed little progression over a 3-year period, but their VBR significantly increased during that same period of time. This increase occurred in healthy older adults who did not develop serious medical problems during the course of the 3-year study. In two of the subjects, with the largest increases in both WMH and VBR, there was a change in their health status.     

静息态功能磁共振成像临床应用扫描时间的优化研究

目的探讨静息态fMRI临床应用的最优化扫描时问。方法采用分数低频振荡振幅（fALFF）值观察16例亚急性期脑桥单发梗死患者（脑梗死组）静息态fMRI扫描6和12min时各脑区默认网络,并与年龄、性别相匹配的正常对照者（对照组）脑默认网络激活范围和强度进行比较。结果静息态fMRI扫描6和12min时,两组受试者各脑区默认网络均被激活,其中对照组两次扫描的脑区包括扣带回前后部、前楔叶、双侧角回和顶下小叶、前额叶,与以往对照者的脑默认网络研究结果相似;4个经典脑区的默认网络在不同测量时间点（6和12min）的激活程度,差异无统计学意义（均P〉0．05）。脑梗死组患者两个测量时间点均获得与对照组相同的默认网络经典脑区,且两个测量时间点的激活程度差异亦无统计学意义（均P〉0．05）,但12min时扫描的头动参数略大于6min时。结论脑梗死组患者静息态fMRI以扫描6min为更优化时间,对临床疾病的研究具有重要参考价值。     

静息态功能磁共振成像临床应用扫描时间的优化研究

目的探讨静息态fMRI临床应用的最优化扫描时间。方法采用分数低频振荡振幅(fALFF)值观察16例亚急性期脑桥单发梗死患者(脑梗死组)静息态fMRI扫描6和12 min时各脑区默认网络,并与年龄、性别相匹配的正常对照者(对照组)脑默认网络激活范围和强度进行比较。结果静息态fMRI扫描6和12 min时,两组受试者各脑区默认网络均被激活,其中对照组两次扫描的脑区包括扣带回前后部、前楔叶、双侧角回和顶下小叶、前额叶,与以往对照者的脑默认网络研究结果相似;4个经典脑区的默认网络在不同测量时间点(6和12 min)的激活程度,差异无统计学意义(均P>0.05)。脑梗死组患者两个测量时间点均获得与对照组相同的默认网络经典脑区,且两个测量时间点的激活程度差异亦无统计学意义(均P>0.05),但12 min时扫描的头动参数略大于6 min时。结论脑梗死组患者静息态fMRI以扫描6 min为更优化时间,对临床疾病的研究具有重要参考价值。     

项目记忆和源记忆的功能磁共振成像研究

目的探讨项目记忆和源记忆的神经基础及其是否存在性别差异。方法健康男女各8名，实验材料为504个高频双汉字词，项目记忆和源记忆实验任务，Block设计，GE1．5T采集功能磁共振成像（mRI）数据，用SPM99分析，得到男女脑功能激活图（P〈0．002，体素块〉20）。结果在P〈0．002，体素块〉20时，女性项目记忆激活双前额叶背外侧BA6（激活数目左右侧分别为62和11个），源记忆较多激活左前额叶背外侧BA6／46（激活数目为59个）；男性项目记忆激活右前额叶背外侧BA6／46（激活数目为64个），源记忆激活双前额叶背外侧BA6（左右侧分别为9和40个）。结论项目记忆更多激活右侧前额叶背外侧，而源记忆更多激活左侧前额叶背外侧。女性较多地引起左前额叶背外侧激活；而男性较多地引起右前额叶背外侧激活。     

复发性视神经炎静息态低频振幅功能磁共振成像研究

目的研究复发性视神经炎患者异常神经功能活动脑区的分布差异,探讨基线神经功能及其与临床的关系。方法采用基于低频振幅(ALFF)的静息态f MRI技术对35例复发性视神经炎患者进行研究,并与50例性别、年龄和受教育程度相匹配的正常对照者进行比较,并分析m ALFF值改变脑区与病程、同步听觉系列加法测验(PASAT)评分和视力之间的相关性。结果与正常对照组相比,复发性视神经炎组患者左侧楔叶/楔前叶、左侧颞上回、双侧颞下回、双侧舌回和右侧枕中回m ALFF值降低(P0.01),而双侧额下回和左侧额叶内侧回m ALFF值增加(P0.01)。复发性视神经炎患者仅左侧颞上回(r=0.403,P0.05)和右侧舌回(r=0.472,P0.05)m ALFF值与病程呈正相关。结论静息态f MRI可以检出复发性视神经炎患者参与视觉信息处理的颞枕叶神经功能降低,以及与脑默认网络相关的额叶神经功能增强,为早期评价视神经炎患者神经功能和预测预后提供客观依据。