腰背痛患者静息态fMRI的脑功能局部一致性研究

目的 利用功能磁共振成像(fMRI)技术探讨静息状态下腰背痛患者脑局部一致性(ReHo)变化的特点. 方法 选择自2011年8月至2012年1月南方医科大学珠江医院康复医学科招募的15例年龄、性别和文化程度相近的健康者作为受试者,向其右侧腰背部肌肉注射0.3 mL30g/L的高渗盐水制造腰背痛模型,采用3.0T MR仪分别在注射前、注射后进行静息状态fMRI扫描,所得数据进行配对t检验,比较疼痛及非疼痛状态下静息态脑功能的局部一致性差异. 结果 与正常状态相比,腰背痛受试者ReHo增高的脑区有:双侧前额叶内侧、左额下回、右额中回、右小脑扁桃体、右脑桥、右岛叶、右尾状核、右楔前叶、右海马旁回、后扣带回;ReHo减低的脑区有:右颞上回、左颞中回、左中央前回、左中央后回、左海马旁回、左梭状回、左前扣带回、左顶上小叶、右顶下小叶(P＜0.005,体素值≥10). 结论 静息状态下腰背痛患者部分脑区存在脑活动区域一致性异常.     

抑郁症与正常人静息态脑功能变化对照研究

目的:利用功能磁共振成像(functional magnetic resonance imaging,fMRI)技术,研究静息状态下重性抑郁症患者经抗抑郁药治疗前后脑局部一致性变化的特点. 方法:20例重性抑郁症患者(抑郁症组),以20名在性别、年龄、受教育年限均与之相匹配的健康人作为对照(对照组),在抗抑郁治疗前和治疗10周进行静息状态fMRI扫描. 结果:与治疗前比较,抑郁症组治疗后大脑左侧黑质、左额中回(BA9,BA10)、左额内侧回(BA10)、左颞中回(BA21)、右额中回(BA11)、右额内侧回(BA25)、右额下回(BA45)及右颞上回(BA38)局部一致性减低.与对照组比较,抑郁症组治疗前双侧楔前叶(BA7)局部一致性增高,而治疗后右前扣带回腹侧(BA31)、右额下回(BA46)、右额内侧回(BAIO)及左海马旁回(BA36)局部一致性减低. 结论:静息状态下抑郁症患者存在部分脑功能异常,经抗抑郁治疗后可逆转.     

以妄想为主的男性精神分裂症患者内侧前额叶功能连接的静息态磁共振成像研究

目的:利用静息态功能性磁共振成像(fMRI)技术,观察以妄想为主的男性精神分裂症患者内侧前额叶(MPFC)的功能连接. 方法:对17例以妄想为主的男性精神分裂症患者(患者组)和17例年龄、利手、性别、受教育程度与患者组均匹配的健康者(对照组)进行静息态fMRI扫描.通过分析MPFC与大脑其他区域的低频fMRI信号波动的相关性,观察MPFC的功能连接.将患者组和对照组在静息状态下MPFC的脑功能连接活动进行相关分析,设P＜0.005且体素范围(K值)≥12为相关具有显著差异. 结果:与对照组相比,患者组MPFC与右颞上回、右额上回及双侧额中回、右海马、右杏仁核、眶额叶、右海马旁回的功能连接减低;与左枕叶中部、左顶下小叶及左小脑前叶的功能连接增强.结论:静息态下以妄想为主的男性精神分裂症患者MPFC与默认网络其他结构的功能连接存在异常.     

抑郁症患者岛叶-皮质静息态功能连接的观察北大核心CSCD

目的探讨未服药抑郁症患者静息态岛叶功能连接特征。方法选取50例未服药的抑郁症患者(抑郁症组)和51名健康对照者(对照组)进行静息态fMRI(rs-fMRI)扫描,对rs-fMRI数据进行常规预处理并基于岛叶分区为双侧岛叶前部、双侧岛叶中部、双侧岛叶后部6个种子点进行全脑功能连接分析,采用双样本t检验比较2组间脑功能连接值的差异,经过不依赖阈值集群增强(threshold-free cluster enhancement,TFCE)的多重比较校正,并将差异有统计学意义脑区的功能连接值与HAMD24评分等临床变量进行相关分析。结果与对照组相比,抑郁症组左侧岛叶前部与双侧前扣带回之间功能连接减低(t=-4.83,P<0.05,TFCE校正),左侧岛叶前部与左侧额中回、双侧后扣带回/楔前叶之间功能连接增强(t=4.08、4.42,均P<0.05,TFCE校正)。左侧岛叶前部与双侧前扣带回(r=-0.125,P=0.387)、左侧额中回(r=0.149,P=0.302)、双侧后扣带回/楔前叶(r=-0.207,P=0.148)的功能连接值与HMAD24评分无相关性。结论抑郁症患者可能存在左侧岛叶前部与边缘系统、额叶皮质功能连接异常,包括岛叶-前扣带回连接减弱,岛叶-额叶、岛叶-后扣带回/楔前叶连接增高。     

抑郁症静息态默认状态网络内功能连接的初步探讨

目的 通过分析静息态下抑郁症患者默认状态网络内脑区间功能连接效能,探讨默认状态网络在抑郁症病理机制中的作用.方法 15例符合中国精神障碍分类及诊断标准第3版(CCMD-3)抑郁发作和美国精神障碍诊断与统计手册第4版(DSM-Ⅳ)重性抑郁症诊断标准的首发抑郁症患者与14名正常对照完成功能磁共振成像扫描.分析受试者默认状态网络内脑区的功能连接强度并比较其组问差异.结果 与正常对照比较,抑郁症患者双侧前额中部与楔前叶、双侧后扣带回与前额中部、右后扣带回与楔前叶、双侧前扣带回腹侧与前额中部的功能连接减低(P＜0.05).结论 静息态下抑郁症患者默认状态网络内脑区间的连接效能存在异常,这可能在抑郁症的病理机制中发挥了重要作用.     

老年抑郁症首次发病与复发患者脑结构的磁共振研究

目的:基于磁共振探讨首发与复发老年抑郁症患者脑结构特点。方法:对首发与复发老年抑郁症患者30例(首发组20例,复发组10例)和正常人30名(正常对照组)进行脑磁共振成像检查并运用弥散张量成像(DTI)扫描,比较首发与复发抑郁症患者与正常对照组的异常脑区以及首发与复发患者脑白质、灰质容量及白质各向异性分数(FA)值的差异。结果:与正常对照组比较,患者组双侧额叶、右顶叶、左楔叶、左海马回灰质以及左颞上回白质T1信号强度减低;右扣带回灰质T1信号及白质T1信号强度升高(P0.01,像素集合30)。首发组和复发组患者脑白质容量未发现显著差异脑区,但复发组右海马区灰质容量较首发组明显减小(P0.01,像素集合30)。与首发组比较,复发组右额中回、左颞中回白质FA值减低(P均0.01,像素集合30)。结论:首发与复发老年抑郁症患者可能存在前额叶及右扣带回功能缺陷;双侧海马区灰质容量可能与临床症状有关。     

右侧颞叶癫痫患者后扣带功能和结构连接与警觉功能的相关性研究

目的利用静息态功能磁共振(functional magnetic resonance imaging,fMRI)及弥散张量成像(diffusiontensor imaging,DTI)技术探讨右侧颞叶癫痫(right temporal lobe epilepsy,rTLE)患者后扣带回功能与结构连接的改变及其与警觉功能关系。方法本实验纳入17例rTLE患者和21例健康对照,对所有被试进行静息态fMRI及DTI扫描、注意网络测试(attention network test,ANT)评估警觉功能。结合静息态f MRI和DTI分析rTLE患者后扣带回功能连接和纤维的微结构改变,并对功能和结构与警觉行相关分析。结果与健康对照相比,rTLE患者固有警觉(intrinsic alertness,IA)与位相性警觉(phasic alertness,PA)的平均反应时间均显著延长(t=-2.771,-2.671;P=0.009,0.011),rTLE患者右后扣带回FA值显著降低(t=-2.136,P=0.040),rTLE患者左后扣带回与右颞极-颞中回、左颞下回、左额上-额中回、右后扣带回的功能连接(functional connectivity,FC)下降(P0.05,Alpha Sim校正,体素值46),右后扣带回与右颞极-颞中回、右海马、右海马旁回、左后扣带回的FC下降(P0.05,Alpha Sim校正,体素值43)。rTLE患者左后扣带回与左额上-额中回间下降的FC与警觉效应行为学成绩呈负相关(r=-0.724,P=0.001),右后扣带回与左后扣带回间下降的FC与固有警觉(r=-0.484,P=0.049)及位相性警觉呈负相关(r=-0.515,P=0.035)。结论 rTLE患者后扣带回警觉功能网络完整性受到破坏,rTLE患者右后扣带回纤维束显著受损,rTLE患者后扣带回间及左后扣带回与左额上-额中回间的功能连接下降可导致警觉功能下降。     

抑郁症患者静息状态的功能磁共振成像研究

目的 了解在静息状态下抑郁症患者脑区的局部一致性特点.方法 采用功能磁共振成像(fMRI)技术,检测静息状态下27例抑郁症患者(患者组)和性别、年龄、受教育程度均与患者相匹配的27名正常人(对照组)的脑功能活动,并对两组进行比较.利用局部一致性方法 分析fMRI数据,用SPM2软件进行配对t检验(P＜0.005).结果 与对照组相比,患者组双侧额中回、右额下回、右颞上回、左前扣带回、右后扣带回、右岛叶、双侧豆状核、双侧屏状核、左尾状核局部一致性显著增高(P＜0.005,未校正,体素值＞10);未显示脑区有明显的局部一致性减低.结论 抑郁症患者神经环路脑区局部在静息状态下具有很高的一致性,其局部一致性的增高可能参与了抑郁症的代偿机制.     

创伤后应激障碍患者杏仁核为主的边缘系统静息态脑功能磁共振研究

目的 观察静息状态下创伤后应激障碍(posttraumatic stress disorder,PTSD)患者以杏仁核为主的脑区的脑功能改变.方法 采用基于低频振幅(amplitude of low frequency fluctuation,ALFF)算法的静息功能磁共振成像技术(fMRI)对10例临床确诊的PISD患者和10例性别、年龄及受教育年限匹配的正常对照进行静息fMRI检查,采用t检验比较两组的杏仁核等脑区基于血氧水平依赖活动的差异.结果 与正常对照组相比,PTSD患者组右侧杏仁核ALFF活性明显增加(P<0.01),海马旁回、钩回等边缘系统其他脑区亦见ALFF活性增加(P<0.01),而前额叶、岛叶及楔前叶ALFF活性减低(P<0.01).结论 PTSD患者静息态下包括杏仁核在内的边缘系统多个脑区活动增强,前额叶、岛叶、楔前叶等脑区功能抑制.     

抑郁症首次发病患者静息态脑功能局部一致性的研究

目的 利用功能磁共振(fMRI)和局部一致性(regional homogeneity,ReHo)探讨抑郁症首次发病(以下简称首发)患者在静息态脑功能是否存在异常及异常部位.方法 对34例符合美国精神疾病诊断与统计手册第4版诊断标准的首发抑郁症患者(抑郁症组)和34名性别、年龄、文化程度匹配的健康志愿者(对照组)进行静息态fMRI扫描.结果 抑郁症组静息态脑血氧水平依赖信号的ReHo高于对照组的脑区有左侧额叶眶回、顶下小叶、颞上回,右侧额内侧回、顶下小叶、小脑后叶;低于对照组的脑区有左颞下回、右颞上同和胼胝体、双侧后扣带回(P＜0.005,K≥10).结论首发抑郁症患者在静息态存在多个腩区功能活动的异常,并可能和抑郁症的病理机制有关.     

静息状态功能磁共振成像观察轻度阿尔茨海默病后扣带回功能连通性的变化

目的 利用静息状态功能磁共振成像(fMRI)研究阿尔茨海默病(AD)早期后扣带回相关的静息脑网络连通性是如何变化的.方法 运用fMRI研究了16例轻度AD患者和16名健康对照者在静息状态后扣带回的功能连通性.与后扣带回有功能连通性的脑区是通过检测低频波动信号的时程相关性获得的.应用通用的SPM2图像统计软件计算组间和组内连通性差异,激活区阈值设置:P<0.01(校正),像素范围>5.利用SPM2软件随机效应分析t检验(经校正P<0.01,t=2.47,像素范围>5),比较患者组和对照组连通性激活的脑区.结果 与后扣带回有功能连通性减弱的脑区包括前额叶中线区、楔前叶、双侧视皮质、双侧颞下回、左侧海马、右侧丘脑、右侧额叶背外侧区;偏左侧化的连通性增高的脑区包括前额叶中线区、左侧颞下回、左侧基底节区、双侧额叶背外侧区及左侧中央前区.结论 与后扣带回相关的静息状态脑网络连通性减低与AD早期情节记忆损害和高级视觉功能损害有关系,轻度AD保留着功能连接的重塑性以便维持脑功能.静息fMRI是一种探索AD脑功能机制的适宜方法.     

Patterns of altered functional connectivity in mesial temporal lobe epilepsy

Purpose: In mesial temporal lobe epilepsy (MTLE) the epileptogenic area is confined to the mesial temporal lobe, but other cortical and subcortical areas are also affected and cognitive and psychiatric impairments are usually documented. Functional connectivity methods are based on the correlation of the blood oxygen level dependent (BOLD) signal between brain regions, which exhibit consistent and reproducible functional networks from resting state data. The aim of this study is to compare functional connectivity of patients with MTLE during the interictal period with healthy subjects. We hypothesize that patients show reduced functional connectivity compared to controls, the interest being to determine which regions show this reduction. Methods: We selected electroencephalography–functional magnetic resonance imaging (EEG‐fMRI) resting state data without EEG spikes from 16 patients with right and 7 patients with left MTLE. EEG‐fMRI resting state data of 23 healthy subjects matched for age, sex, and manual preference were selected as controls. Four volumes of interest in the left and right amygdalae and hippocampi (LA, RA, LH, and RH) were manually segmented in the anatomic MRI of each subject. The averaged BOLD time course within each volume of interest was used to detect brain regions with BOLD signal correlated with it. Group differences between patients and controls were estimated. Key Findings: In patients with right MTLE, group difference functional connectivity maps (RMTLE ? controls) showed for RA and RH decreased connectivity with the brain areas of the default mode network (DMN), the ventromesial limbic prefrontal regions, and contralateral mesial temporal structures; and for LA and LH, decreased connectivity with DMN and contralateral hippocampus. Additional decreased connectivity was found between LA and pons and between LH and ventromesial limbic prefrontal structures. In patients with left MTLE, functional connectivity maps (LMTLE ? controls) showed for LA and LH decreased connectivity with DMN, contralateral hippocampus, and bilateral ventromesial limbic prefrontal regions; no change in connectivity was detected for RA; and for RH, there was decreased connectivity with DMN, bilateral ventromesial limbic prefrontal regions, and contralateral amygdala and hippocampus. Significance: In unilateral MTLE, amygdala and hippocampus on the affected and to a lesser extent on the healthy side are less connected, and are also less connected with the dopaminergic mesolimbic and the DMNs. Changes in functional connectivity between mesial temporal lobe structures and these structures may explain cognitive and psychiatric impairments often found in patients with MTLE.     

Differential connectivity of perirhinal and parahippocampal cortices within human hippocampal subregions revealed by high-resolution functional imaging

Numerous studies support the importance of the perirhinal cortex (PRC) and parahippocampal cortex (PHC) in episodic memory. Theories of PRC and PHC function in humans have been informed by neuroanatomical studies of these regions obtained in animal tract-tracing studies, but knowledge of the connectivity of PHC and PRC in humans is limited. To address this issue, we used resting-state functional magnetic resonance imaging to compare the intrinsic functional connectivity profiles associated with the PRC and PHC both across the neocortex and within the subfields of the hippocampus. In Experiment 1, we acquired standard-resolution whole-brain resting-state fMRI data in 15 participants, and in Experiment 2, we acquired high-resolution resting-state fMRI data targeting the hippocampus in an independent sample of 15 participants. Experiment 1 revealed that PRC showed preferential connectivity with the anterior hippocampus, whereas PHC showed preferential connectivity with posterior hippocampus. Experiment 2 indicated that this anterior-posterior functional connectivity dissociation was more evident for subfields CA1 and subiculum than for a combined CA2/CA3/dentate gyrus region. Finally, whole-brain analyses from Experiment 1 revealed preferential PRC connectivity with an anterior temporal and frontal cortical network, and preferential PHC connectivity with a posterior medial temporal, parietal, and occipital network. These results suggest a framework for refining models of the functional organization of the human medial temporal lobes in which the PRC and PHC are associated with distinct neocortical pathways that, in turn, may differentially interact with regions along the anterior-posterior axis of the hippocampus.     

Lesion patterns and mechanism of cerebral infarction caused by severe atherosclerotic intracranial internal carotid artery stenosis

The hippocampus is believed to have close relationship with many cerebral cortexes and constitute memory network to modulate and facilitate communication, which makes it especially interesting and meaningful in the study of functional connectivity in mild cognitive impairment (MCI). However, functional connectivity between the hippocampus and other brain regions remains unclear in MCI. Furthermore, the longitudinal changes of the hippocampal connectivity have not been reported. In the study, resting state functional MRI (fMRI) was used to examine changes in hippocampal connectivity comparing 14 patients and 14 healthy age-matched controls. We found that functional connectivity between the hippocampus and a set of regions was disrupted in MCI, these regions are: the right frontal lobe, the bilateral temporal lobe and the right insular. While, the left posterior cingulate cortex, precuneus, hippocampus, caudate and right occipital gyrus showed increased connectivity to the hippocampus in MCI. Additionally, we traced the seven MCI patients and compared the hippocampal connectivity in initial stage and 3 years later stage. Several regions presented decreased connectivity to the hippocampus after 3 years. Finally, the hippocampal connectivity with some regions showed significant correlation with the cognitive performance of patients. Based on these findings, the decreased hippocampal connectivity might indicate reduced integrity of hippocampal cortical memory network in MCI. In addition, the increased hippocampal connectivity suggested compensation for the loss of memory function. With the development of the disease, the hippocampal connectivity may lose some compensation and add some more disruption due to the pathological changes.     

长期海洛因成瘾者前额叶功能连接的静息态fMRI研究

目的 利用静息态fMRI探讨长期海洛因成瘾者前额叶功能连接的变化情况.方法 13例长期海洛因成瘾者和14例正常者接受静息态fMRI检查,对数据进行相关的预处理后,以前额叶为种子点与全脑每个体素进行相关分析,比较海洛因成瘾组与正常对照组前额叶功能连接的变化情况.结果 以左侧前额叶为种子点进行功能连接分析,海洛因成瘾组左侧前额叶与左侧海马、右侧前扣带回、左侧额中回、右侧额中回、右侧楔前叶功能连接明显低于正常对照组:以右侧前额叶为种子点进行功能连接分析,海洛因成瘾组右侧前额叶与左侧眶额叶、左侧额中回功能连接明显低于正常对照组.结论 长期海洛因成瘾者前额叶与相关脑区的功能连接减弱,前额叶可能参与了海洛因成瘾的维持与戒断后复吸.

Abstract：

Objective To explore the changes of functional connectivity of the prefrontal cortex in chronic heroin addicts under resting-state functional MRI (fMRI). Methods Resting fMRI examination was performed on 13 chronic heroin addicts and 14 healthy volunteers. After pre-processing the resting-state fMRI data, the prefrontal cortex was selected as the seed region, with which a whole-brain voxel temporal correlation in Iow frequency fMRI fluctuations was analyzed and the changes of functional connectivity of the prefrontal lobe in both chronic heroin addicts and healthy volunteers were calculated with SPM5 software. Results Compared with that in the control group, the functional connectivity between the left prefrontal cortex and the left hippocampus, right anterior cingulate, left middle frontal gyrus, right middle frontal gyrus, right precuneus in the heroin addiction group was significantly decreased. The functional connectivity between the right prefrontal cortex and the left orbital frontal cortex, left middle frontal gyrus in thc heroin addiction group was also significantly decreased as compared with that in the control group. Conclusion Functional connectivity of prefrontal cortex in chronic heroin addicts decreases, indicating that the prefrontal cortex may be involved in the maintenance of heroin addiction and relapse after withdrawal.     

Cross hippocampal influence in mesial temporal lobe epilepsy measured with high temporal resolution functional magnetic resonance imaging

Purpose Mesial temporal lobe epilepsy (mTLE) is a chronic disorder with spontaneous seizures recurring for years, or even decades. Many structural and functional changes have been detected in both the seizure focus and distal regions throughout the brain over this duration that may reflect the development of epileptogenic networks. Resting state functional magnetic resonance imaging (fMRI) connectivity mapping has the potential to elucidate and quantify these networks. The network between the left and right hippocampus may very likely be one of the most susceptible to changes due to long‐term seizure propagation effects. Therefore, the objective of this study was to quantify cross hippocampal influence in mTLE using high temporal resolution fMRI, and to determine its relationship with disease duration. Methods fMRI images were acquired in the resting (interictal) state with 500 ms temporal resolution across the temporal lobes of 19 mTLE patients (13 left, 6 right). The left and right hippocampi were identified on each subject’s images using both structurally defined and functionally defined boundaries. The cross hippocampal influence was quantified in two ways for each pair of regions: (1) the nondirectional hippocampal functional connectivity calculated as the Pearson’s correlation between the average time series in the left and the right hippocampus regions, and (2) the Granger causality (GC) laterality measure, which implies directional influence by determining temporal precedence. Each of these measures was correlated with age, age of onset, and disease duration across subjects to investigate relationship to disease progression. Key Findings The hippocampal connectivity was not significantly different between patients with left and right mTLE using either the structurally or the functionally defined regions. Across all patients, hippocampal connectivity was not correlated significantly with age of onset or duration of disease. However, as duration of disease increased after 10 years (nine patients), the hippocampal connectivity increased linearly. Using the functionally defined regions, the GC laterality was increased in the right mTLE over the left mTLE, indicating that the left hippocampus was influencing the right hippocampus more than the right influencing left. This was also positively correlated with age of onset. Furthermore, like hippocampal connectivity, the relationship between GC laterality and duration of disease changes after 10 years duration of disease. After this duration, the GC laterality was positive in the three of three patients with right mTLE (left influencing right), whereas the GC laterality was negative in five of six patients with left mTLE (right influencing left). Significance This study reveals a relationship between fMRI functional connectivity and causal influence of the left and right hippocampi and duration of disease in mTLE. During the interictal state, the interhemispheric hippocampal connectivity initially is disrupted and then linearly increases as the epilepsy progresses longer than 10 years. This increase in connectivity appears to be due to the hippocampus contralateral to the epileptogenic focus exerting more influence over the ipsilateral hippocampus. These findings may have implications in understanding the functional development of epileptic networks and possibly prediction of surgical outcome of mTLE.     

Lateralization of temporal lobe epilepsy using resting functional magnetic resonance imaging connectivity of hippocampal networks

Purpose: Early surgical intervention can be advantageous in the treatment of refractory temporal lobe epilepsy (TLE). The success of TLE surgery relies on accurate lateralization of the seizure onset. The purpose of this study was to determine whether resting functional MRI (fMRI) connectivity mapping of the hippocampus has the potential to complement conventional presurgical evaluations in distinguishing left from right TLE. In addition, we sought to determine whether this same network might separate patients with favorable from unfavorable postoperative outcomes. Methods: Resting fMRI acquisitions were performed on 21 patients with TLE and 15 healthy controls. The patients included seven patients with left TLE and seven patients with right TLE with seizure-free postoperative outcome, and five patients with left TLE and two patients with right TLE with recurring seizures after surgery. Functional connectivity maps to each hippocampus were determined for each subject and were compared between the controls and the seizure-free patients with left TLE and with right TLE. The one network identified was then quantified in the patients with TLE and recurring seizures. Key Findings: The resting functional connectivity between the right hippocampus and the ventral lateral nucleus of the right thalamus was the most statistically significant network to distinguish between seizure-free patients with left TLE and with right TLE with high sensitivity and specificity. This connectivity was also significantly greater in the seizure-free patients with left TLE than the healthy controls. Finally, six of the seven patients in whom seizures recurred after surgery had connectivity values in this network unlike those who were seizure-free. Significance: This study identified a region in the ventral lateral nucleus of the right thalamus whose connectivity to the hippocampi separates left from right TLE subjects. This suggests that the quantification of resting-state functional magnetic resonance imaging (MRI) connectivity across this network may be a potential indicator of lateralization of TLE that may be added to other presurgical MRI assessments. Further validation in a larger, independent cohort is required.     

Functional connectivity with the hippocampus during successful memory formation

Although it is well established that the hippocampus is critical for episodic memory, little is known about how the hippocampus interacts with cortical regions during successful memory formation. Here, we used event-related functional magnetic resonance imaging (fMRI) to identify areas that exhibited differential functional connectivity with the hippocampus during processing of novel objects that were subsequently remembered or forgotten on a postscan test. Functional connectivity with the hippocampus was enhanced during successful, as compared with unsuccessful, memory formation, in a distributed network of limbic cortical areas-including perirhinal, orbitofrontal, and retrosplenial/posterior cingulate cortex-that are anatomically connected with the hippocampal formation. Increased connectivity was also observed in lateral temporal, medial parietal, and medial occipital cortex. These findings demonstrate that successful memory formation is associated with transient increases in cortico-hippocampal interaction.     

Abnormal connectivity in the posterior cingulate and hippocampus in early Alzheimer's disease and mild cognitive impairment

BackgroundBrain imaging studies of early Alzheimer's disease (AD) have shown decreased metabolism predominantly in the posterior cingulate cortex (PCC), medial temporal lobe, and inferior parietal lobe. This study investigated functional connectivity between these regions, as well as connectivity between these regions and the whole brain.MethodsFunctional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) studies were performed in subjects with early AD, mild cognitive impairment (MCI), and normal controls.ResultsThe data indicate both decreased fiber connections and disrupted connectivity between the hippocampus and PCC in early AD. The MCI group showed reduced fiber numbers derived from PCC and hippocampus to the whole brain.ConclusionsThe fMRI and DTI results confirmed decreased connectivity from both the PCC and hippocampus to the whole brain in MCI and AD and reduction in connectivity between these two regions, which plausibly represents an early imaging biomarker for AD.     

Resting state functional connectivity of the hippocampus associated with neurocognitive function in left temporal lobe epilepsy

The majority of patients with temporal lobe epilepsy (TLE) experience disturbances of episodic memory from structural damage or dysfunction of the hippocampus. The objective of this study was to use functional Magnetic Resonance Imaging (fMRI) to identify regions where resting state connectivity to the left hippocampus (LH) is correlated with neuropsychological measures of verbal memory retention in TLE patients. Eleven left TLE (LTLE) patients and 15 control subjects participated in resting state fMRI scans. All LTLE patients underwent neuropsychological testing. Resting state functional connectivity maps to the LH were calculated for each patient, and subsequently used in a multiple regression analysis with verbal memory retention scores as a covariate. The analysis identified brain regions whose connectivity to the LH was linearly related to memory retention scores across the group of patients. In LTLE patients, right sided (contralateral) clusters in the precuneus and inferior parietal lobule (IPL) exhibited increased connectivity to the LH with increased memory retention score; left sided (ipsilateral) regions in the precuneus and IPL showed increased connectivity to the LH with decreased retention score. Patients with high memory retention scores had greater connectivity between the LH–right parietal clusters than between the LH–left parietal clusters; in contrast, control subjects had significantly and consistently greater LH–left hemisphere than LH–right hemisphere connectivity. Our results suggest that increased connectivity in contralateral hippocampal functional pathways within the episodic verbal memory network represents a strengthening of alternative pathways in LTLE patients with strong verbal memory retention abilities. Hum Brain Mapp 35:735–744, 2014. © 2012 Wiley Periodicals, Inc.