人脑默认网络方向图：基于7TfMRI的动态因果模型

近年来,默认网络是认知神经科学领域的研究热点之一,已有研究报告它可能参与了多种认知活动,而且某些精神疾病也与其异常活动相关.但默认网络内主要脑区之间的有向连接关系(有效连接模式)尚不明确.本研究使用国际前沿的谱动态因果模型算法,基于7T高分辨率静息态功能磁共振数据,对默认网络4个核心脑区之间的有效连接模式进行了探索.实验结果发现,默认网络内后扣带回接受内侧前额叶、双侧顶下叶的信息输入,可能扮演着信息集合中心的角色,而双侧顶下叶对内侧前额叶、后扣带回都有信息输入,在默认网络内可能起到信息驱动和调节的功能.本研究首次报道了基于7T功能磁共振数据得到的默认网络有向连接图谱,对于我们更深入理解默认网络的功能具有帮助,对相关精神疾病的研究具有潜在的参考应用价值.     

患抑郁症成瘾者静息态脑功能变化的初步探讨

目的:探讨静息态下患抑郁症的成癌者相对于非抑郁症成瘾者脑功能的进一步变化.方法:25例符合阿片类物质成癍标准及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患抑郁症成癌者与20例非抑郁症成瘾者对照完成功能磁共振成像扫描.比较抑郁症成瘾者相对于非抑郁症成瘾者的脑区功能变化.结果:与非抑郁症对照组比较,患抑郁症成癌者双侧前额中部,双侧扣带回,楔前叶脑功能减低(P＜0.05).结论:静息态下患抑郁症成瘾者特定脑区功能进一步减低,这可能在成瘟者患抑郁症的病理机制中发挥了重要作用.     

封面图片介绍

正脑默认网络(default mode network,DMN)是由在脑处于静息状态时相互联系、维持健康代谢活动的若干脑区组成的网络,主要包括楔后扣带回/前楔叶(PCC/Precuneus)、内侧前额叶(MPFC)、双侧角回(bilateral AG)、双侧外侧颞叶(bilateral lateral temporal cortex,LTC)、双侧海马(bilateral hippocampus,HIP)等脑区,在个体从事如监控外界环境、记忆提取和控制自身心理状态等多种事务中发挥着重要作用。脑默认网络与阿兹海     

带状疱疹后遗神经痛患者脑基础活动改变的功能核磁共振研究

带状疱疹后遗神经痛(postherpetic neuralgia,PHN)是临床上一种慢性顽固性神经病理性疼痛,然而,对于其潜在的中枢机制还知之甚少.为了进一步探讨带状疱疹后遗神经痛患者的相关脑区活动,利用功能核磁共振成像低频振幅振荡(ALFF)技术观察带状疱疹后遗神经痛患者的基础脑区活动.8名带状疱疹后遗神经痛患者与8名性别、年龄相匹配的健康者行静息态功能磁共振(f MRI)成像扫描,用SPM8中的多重回归分析,在控制被试年龄、性别、教育年限的影响下,将每个体素的ALFF值同每个被试的病程、视觉模拟评分(visual analog scale,VAS)进行相关分析.与健康志愿者相比,PHN组与VAS评分相关的ALFF值增高的脑区有:右侧小脑后叶、前额叶背外侧区域(BA11/46/47)、右侧顶叶(BA40)、右侧舌回(BA17/18/19);与VAS评分相关的ALFF值降低的脑区有:右侧颞中回(BA21)、左侧舌回(BA17/18)、右侧小脑前叶、左侧后扣带回(BA30/19)和右侧中央前回(BA3/4/6);PHN组与病程相关的ALFF值增高的脑区有:右侧小脑后叶、前额叶背外侧区域(BA9/10/11/47)、左侧颞上回(BA38)、右侧顶叶和右侧舌回(BA17/18/19);与病程相关ALFF值降低的脑区有:左侧海马旁回(BA28)、右侧小脑前叶、左侧扣带回(BA24)、右侧颞上回(BA13)、左侧中央前回和右侧顶下小叶(BA39/40).研究结果提示,涉及疼痛的情绪、警觉行为、注意的脑区在带状疱疹后遗痛慢性疼痛的产生和维持中发挥重要作用.     

默认模式网络与阿尔茨海默病

默认模式网络（default-mode network,DMN）是由在脑处于静息状态时相互联系、维持健康代谢活动的若干脑区组成的网络,主要包括楔前叶/后扣带回皮质、顶下小叶、内侧前额叶皮层的背侧和腹侧、内侧颞叶以及海马等脑区,在个体从事如自传性记忆提取、监控外界环境以及控制自身心理状态等多种事务中发挥着重要作用,且与记忆有关的结构被证实是DMN的核心成分。现已有研究表明DMN功能障碍可能会诱导β-淀粉样蛋白沉积形成老年斑,并最终导致阿尔茨海默病（Alzheimer’s disease,AD）的发病。因此,越来越多的学者将研究的重心放在了DMN功能障碍与AD发病的关系上。本文就近年来有关DMN组成、功能特别是与AD发病关系的研究作一简要回顾。     

精神分裂症患者暴力行为与全脑皮质厚度、甲状腺功能和Th17相关炎症因子的相关性分析

目的:探讨精神分裂症患者暴力行为与全脑皮质厚度、甲状腺功能和辅助性T细胞17(Th17)相关炎症因子的相关性。方法:选择常德市康复医院2020年1月~2021年4月收治的精神分裂症患者82例为研究对象。采用修订版外显攻击行为量表(MOAS)评分将患者分成暴力组(n=37)与无暴力组(n=45)。比较两组全脑皮质厚度、甲状腺功能、Th17相关炎症因子水平,利用Pearson相关系数分析MOAS评分与全脑皮质厚度、甲状腺功能指标和Th17相关炎症因子的相关性。结果:暴力组左侧枕中回、顶上回、顶下角回、顶下缘上回、枕极以及右侧枕上回、顶上回、顶下角回、顶下缘上回皮质厚度低于无暴力组(P<0.05)。暴力组血清游离三碘甲状腺原氨酸(FT₃)、总甲状腺激素(TT₄)、游离甲状腺素(FT₄)、总三碘甲状腺原氨酸(TT₃)、促甲状腺激素(TSH)、白介素-17(IL-17)、白介素-23(IL-23)、转化生长因子-β1(TGF-β1)水平高于无暴力组(P<0.05)。Pearson相关性分析结果显示,精神分裂症患者MOAS评分与左侧枕中回、顶上回、顶下角回、顶下缘上回、枕极以及右侧枕上回、顶上回、顶下角回、顶下缘上回皮质厚度呈负相关,与血清FT₃、TT₄、FT₄、TT₃、TSH、IL-17、IL-23、TGF-β1水平呈正相关(P<0.05)。结论:有暴力行为的精神分裂症患者伴有明显的全脑皮质厚度降低与甲状腺功能指标、Th17相关炎症因子水平升高,这可能对此类患者暴力行为的防治有一定参考意义。     

语言控制和一般领域认知控制的脑机制的重合和分离

双语者能根据不同的场合和交流对象选择目标语言进行交流.已有的研究发现,双语者需要通过抑制控制选择合适的语言.本研究使用功能性核磁共振(f MRI)技术,扫描22名汉-英双语者完成语言切换任务和西蒙切换任务时的脑活动状况,通过联合分析和分离分析的方法,揭示了双语产生过程中语言控制与一般领域的认知控制的脑机制的重合与分离.结果发现,双语产生过程中,语言控制需要使用一般领域的施加抑制和解除抑制机制.其中,语言控制与施加抑制共同涉及了额上回、前辅助运动区/背侧前扣带回、壳核和右侧顶上小叶的活动;语言控制与解除抑制都需要左侧顶上小叶的参与.此外发现,双语控制相比于一般领域的控制,需要特异性地激活左侧中央后回、左侧颞上回、左侧楔前叶、中后部扣带回、后辅助运动区、右侧颞中回、右侧舌回、右侧缘上回和双侧小脑等脑区,以发挥与发音动作、词汇提取、语义记忆有关的认知控制功能.这表明,语言控制与一般领域的认知控制既存在重合的脑机制,也存在分离的脑机制.     

汉字字形认知研究的刺激源设计及在fMRI研究中的应用

目的:评估汉字字形刺激源在汉字认知fMRI研究中的有效性,并对参与汉字处理的脑皮层区域进行定位及初步的量化分析。方法:选择母语为汉语、经利手测试后为右利手且裸眼视力正常(大于等于1．0)的在校大学生10例(男6例,女4例)作为被试。试验任务采用组块设计,将汉字(非字、假字、真字)投射到屏幕上,受试者接受汉字字形图片的视觉刺激,按非字-假字-真字-非字-假字-真字顺序呈现,共6个block。数据处理及统计分析采用国际通用的AFNI软件。结果:左额叶上、中、下回(包括Broca's area)、左中央前回(BA6)、左顶上小叶及顶下小叶(包括缘上回及角回)及双侧枕叶、楔前叶显著激活;左颞叶梭状回(BA37)、右额下回及双侧颞中、上回及扣带回显著激活,左大脑半球的激活体积明显大于右侧大脑半球。结论:本研究设计的汉字字形刺激源结合功能磁共振成像技术可以对汉字处理的相关大脑皮层区域进行定位,为研究人脑加工处理汉字的神经机制提供了一种有效的无创性影像学方法,并应用fMRI技术进一步证实其优势半球为左半球,且需要多种脑区共同参与完成。本试验模式可望成为一种对语言障碍病人进行脑功能检查的有效手段,从而为指导临床治疗和评价预后提供更丰富的信息。     

正常人长时数字记忆信息提取的神经基础的功能磁共振研究

本文旨在通过功能磁共振成像(functional magnetic resonance imaging,fMRI)技术研究正常人进行长时数字记忆信息提取的神经基础。选取22名右利手志愿者进行长时数字记忆任务实验,采用组块设计,记忆任务与对照任务交替进行,同时利用Siemens 1.5T超导型磁共振仪进行fMRI成像,采用SPM99软件进行数据分析,脑功能区定位在Talairach坐标中显示。结果显示被试者在进行长时数字记忆提取任务时,激活最显著的皮层是左侧额中回(Brodmann分区9区,BA9区),另外左额叶内侧回、左额下回、右额下回、扣带回、左顶下小叶、左顶上小叶、右顶上小叶、右颞中回、左枕舌回、左枕中回、右中脑、小脑、右尾状核尾部等结构也有激活,各大脑皮层的激活均呈现明显的左侧半球优势。根据上述结果推论,长时数字记忆由以左侧大脑半球为优势的各脑区共同参与完成,其中左侧额叶外侧面可能是信息提取的重要结构,而其它脑叶及其之间的广泛联系可能在数字信息的加工、处理和存储中起重要作用。     

功能性核磁共振成像技术对原发性三叉神经痛患者脑功能的评估价值及血清IL-1β、TNF-α检测的临床意义

目的:研究功能性核磁共振成像(fMRI)技术对原发性三叉神经痛(ITN)患者静息状态下脑功能的评估价值及血清白细胞介素-1β(IL-1β)、肿瘤坏死因子-α(TNF-α)检测的临床意义。方法:选取2017年2月～2019年2月安徽医科大学附属口腔医院接受诊治的ITN患者共50例进行研究,记为ITN组。另选取同期接受体检的健康人员50例记作健康对照组。两组均于静息状态下行fMRI扫描,比较两组脑区的平均低频振幅率(mfALFF)以及血清IL-1β、TNF-α水平。结果:ITN组左侧的枕中回、枕下回、梭状回、距状裂周围皮层、中央旁回、三角部额下回、右侧背外侧额上回以及左小脑脚1区的mfALFF值高于健康对照组(均P0.05)。ITN组右颞上回、右颞中回、右颞下回、右中央沟盖、右缘上回、右岛盖部颞下回、左前扣带回、扣带旁回、左颞极、颞上回脑区的mfALFF值显著低于健康对照组(均P0.05)。ITN组患者的血清IL-1β、TNF-α水平高于健康对照组(均P0.05)。结论:fMRI对ITN患者静息状态下脑功能的评估价值较高,血清IL-1β、TNF-α水平升高可能与ITN的发病密切相关,可发挥促进疾病发生、发展的作用。     

Identify Changes of Brain Regional Homogeneity in Bipolar Disorder and Unipolar Depression Using Resting-State fMRI

Background

To identify changes in brain activation patterns in bipolar disorder (BD) and unipolar depression (UD) patients.

Methodology/Principal Findings

Resting-state fMRI scans of 16 healthy controls, 17 BD and 16 UD patients were obtained. T-test of normalized regional homogeneity (ReHo) was performed in a voxel-by-voxel manner. A combined threshold of á = 0.05, minimum cluster volume of V = 10503 mm³ (389 voxels) were used to determine ReHo differences between groups. In UD group, fMRI revealed ReHo increases in the left middle occipital lobe, right inferior parietal lobule, right precuneus and left convolution; and ReHo decreases in the left parahippocampalgyrus, right precentralgyrus, left postcentralgyrus, left precentralgyrus and left cingulated. In BD group, ReHo increases in the right insular cortex, left middle frontal gyrus, left precuneus, left occipital lobe, left parietal, left superior frontal gyrus and left thalamus; and ReHo decreases in the right anterior lobe of cerebellum, pons, right precentralgyrus, left postcentralgyrus, left inferior frontal gyrus, and right cingulate. There were some overlaps in ReHo profiles between UD and BD groups, but a marked difference was seen in the thalamus of BD.

Conclusions/Significance

The resting-state fMRI and ReHo mapping are a promising tool to assist the detection of functional deficits and distinguish clinical and pathophysiological signs of BD and UD.     

Mirroring Pain in the Brain: Emotional Expression versus Motor Imitation

Perception of pain in others via facial expressions has been shown to involve brain areas responsive to self-pain, biological motion, as well as both performed and observed motor actions. Here, we investigated the involvement of these different regions during emotional and motor mirroring of pain expressions using a two-task paradigm, and including both observation and execution of the expressions. BOLD responses were measured as subjects watched video clips showing different intensities of pain expression and, after a variable delay, either expressed the amount of pain they perceived in the clips (pain task), or imitated the facial movements (movement task). In the pain task condition, pain coding involved overlapping activation across observation and execution in the anterior cingulate cortex, supplementary motor area, inferior frontal gyrus/anterior insula, and the inferior parietal lobule, and a pain-related increase (pain vs. neutral) in the anterior cingulate cortex/supplementary motor area, the right inferior frontal gyrus, and the postcentral gyrus. The ‘mirroring’ response was stronger in the inferior frontal gyrus and middle temporal gyrus/superior temporal sulcus during the pain task, and stronger in the inferior parietal lobule in the movement task. These results strongly suggest that while motor mirroring may contribute to the perception of pain expressions in others, interpreting these expressions in terms of pain content draws more heavily on networks involved in the perception of affective meaning.     

Task-switching Cost and Intrinsic Functional Connectivity in the Human Brain: Toward Understanding Individual Differences in Cognitive Flexibility

The human ability to flexibly alternate between tasks (i.e., task-switching) represents a critical component of cognitive control. Many functional magnetic resonance imaging (fMRI) studies have explored the neural basis of the task-switching. However, no study to date has examined how individual differences in intrinsic functional architecture of the human brain are related to that of the task-switching. In the present study, we took 11 task-switching relevant areas from a meta-analysis study as the regions of interests (ROIs) and estimated their intrinsic functional connectivity (iFC) with the whole brain. This procedure was repeated for 32 healthy adults based upon their fMRI scans during resting-state (rfMRI) to investigate the correlations between switching cost and the iFC strength across these participants. This analysis found that switch cost was negatively correlated with a set of iFC involved ROIs including left inferior frontal junction, bilateral superior posterior parietal cortex, left precuneus, bilateral inferior parietal lobule, right middle frontal gyrus and bilateral middle occipital gyrus. These connectivity profiles represent an intrinsic functional architecture of task-switching where the left inferior frontal junction plays a hub role in this brain-behavior association. These findings are highly reproducible in another validation independent sample and provide a novel perspective for understanding the neural basis of individual differences in task-switching behaviors reflected in the intrinsic architecture of the human brain.     

Neural Control of Enhanced Filtering Demands in a Combined Flanker and Garner Conflict Task

Several studies demonstrated that visual filtering mechanisms might underlie both conflict resolution of the Flanker conflict and the control of the Garner effect. However, it remains unclear whether the mechanisms involved in the processing of both effects depend on similar filter mechanisms, such that especially the Garner effect is able to modulate filtering needs in the Flanker conflict. In the present experiment twenty-four subjects participated in a combined Garner and Flanker task during two runs of functional magnetic resonance imaging (fMRI) recordings. Behavioral data showed a significant Flanker but no Garner effect. A run-wise analysis, however, revealed a Flanker effect in the Garner filtering condition in the first experimental run, while we found a Flanker effect in the Garner baseline condition in the second experimental run. The fMRI data revealed a fronto-parietal network involved in the processing of both types of effects. Flanker interference was associated with activity in the inferior frontal gyrus, the anterior cingulate cortex, the precuneus as well as the inferior (IPL) and superior parietal lobule (SPL). Garner interference was associated with activation in middle frontal and middle temporal gyrus, the lingual gyrus as well as the IPL and SPL. Interaction analyses between the Garner and the Flanker effect additionally revealed differences between the two experimental runs. In the first experimental run, activity specifically related to the interaction of effects was found in frontal and parietal regions, while in the second run we found activity in the hippocampus, the parahippocampal cortex and the basal ganglia. This shift in activity for the interaction effects might be associated with a task-related learning process to control filtering demands. Especially perceptual learning mechanisms might play a crucial role in the present Flanker and Garner task design and, therefore, increased performance in the second experimental run could be the reason for the lack of behavioral Garner interference on the level of the whole experiment.     

Voxel Based Morphometry Alterations in Mal de Debarquement Syndrome

Background

Mal de debarquement syndrome (MdDS) is a disorder of chronic self-motion perception that occurs though entrainment to rhythmic background motion, such as from sea voyage, and involves the perception of low-frequency rocking that can last for months or years. The neural basis of this persistent sensory perception abnormality is not well understood.

Methods

We investigated grey matter volume differences underlying persistent MdDS by performing voxel-based morphometry on whole brain and pre-specified ROIs in 28 individuals with MdDS and comparing them to 18 age, sex, and handedness matched controls.

Results

MdDS participants exhibited greater grey matter volume in the left inferior parietal lobule, right inferior occipital gyrus (area V3v), right temporal pole, bilateral cerebellar hemispheric lobules VIII/IX and left lobule VIIa/VIIb. Grey matter volumes were lower in bilateral inferior frontal, orbitofrontal, pregenual anterior cingulate cortex (pgACC) and left superior medial gyri (t = 3.0, p<0.005_uncorr). In ROI analyses, there were no volume differences in the middle occipital gyrus (region of V5/MT) or parietal operculum 2 (region of the parietoinsular vestibular cortex). Illness duration was positively related to grey matter volume in bilateral inferior frontal gyrus/anterior insula (IFG/AI), right posterior insula, superior parietal lobule, left middle occipital gyrus (V5/MT), bilateral postcentral gyrus, anterior cerebellum, and left cerebellar hemisphere and vermian lobule IX. In contrast, illness duration was negatively related to volume in pgACC, posterior middle cingulate gyrus (MCC), left middle frontal gyrus (dorsolateral prefrontal cortex-DLPFC), and right cerebellar hemispheric lobule VIIIb (t = 3.0, p<0.005_uncorr). The most significant differences were decreased volume in the pgACC and increased volume in the left IFG/AI with longer illness duration (qFDR_corr <0.05). Concurrent medication use did not correlate with these findings or have a relationship with duration of illness. MdDS participants showed positive correlations between grey matter volume in pgACC and bilateral cerebellar lobules VIII/IX, which was not seen in controls.

Conclusions

Individuals with MdDS show brain volume differences from healthy controls as well as duration of illness dependent volume changes in (a) visual-vestibular processing areas (IPL, SPL, V3, V5/MT), (b) default mode network structures (cerebellar IX, IPL, ACC), (c) salience network structures (ACC and IFG/AI) (d) somatosensory network structures (postcentral gyrus, MCC, anterior cerebellum, cerebellar lobule VIII), and (e) a structure within the central executive network (DLPFC). The identification of these associations may enhance future investigations into how exposure to oscillating environments can modulate brain function and affect motion perception as well cognitive and affective control.     

Toward Probabilistic Diagnosis and Understanding of Depression Based on Functional MRI Data Analysis with Logistic Group LASSO

Diagnosis of psychiatric disorders based on brain imaging data is highly desirable in clinical applications. However, a common problem in applying machine learning algorithms is that the number of imaging data dimensions often greatly exceeds the number of available training samples. Furthermore, interpretability of the learned classifier with respect to brain function and anatomy is an important, but non-trivial issue. We propose the use of logistic regression with a least absolute shrinkage and selection operator (LASSO) to capture the most critical input features. In particular, we consider application of group LASSO to select brain areas relevant to diagnosis. An additional advantage of LASSO is its probabilistic output, which allows evaluation of diagnosis certainty. To verify our approach, we obtained semantic and phonological verbal fluency fMRI data from 31 depression patients and 31 control subjects, and compared the performances of group LASSO (gLASSO), and sparse group LASSO (sgLASSO) to those of standard LASSO (sLASSO), Support Vector Machine (SVM), and Random Forest. Over 90% classification accuracy was achieved with gLASSO, sgLASSO, as well as SVM; however, in contrast to SVM, LASSO approaches allow for identification of the most discriminative weights and estimation of prediction reliability. Semantic task data revealed contributions to the classification from left precuneus, left precentral gyrus, left inferior frontal cortex (pars triangularis), and left cerebellum (c rus1). Weights for the phonological task indicated contributions from left inferior frontal operculum, left post central gyrus, left insula, left middle frontal cortex, bilateral middle temporal cortices, bilateral precuneus, left inferior frontal cortex (pars triangularis), and left precentral gyrus. The distribution of normalized odds ratios further showed, that predictions with absolute odds ratios higher than 0.2 could be regarded as certain.     

Driving and driven architectures of directed small-world human brain functional networks

Recently, increasing attention has been focused on the investigation of the human brain connectome that describes the patterns of structural and functional connectivity networks of the human brain. Many studies of the human connectome have demonstrated that the brain network follows a small-world topology with an intrinsically cohesive modular structure and includes several network hubs in the medial parietal regions. However, most of these studies have only focused on undirected connections between regions in which the directions of information flow are not taken into account. How the brain regions causally influence each other and how the directed network of human brain is topologically organized remain largely unknown. Here, we applied linear multivariate Granger causality analysis (GCA) and graph theoretical approaches to a resting-state functional MRI dataset with a large cohort of young healthy participants (n = 86) to explore connectivity patterns of the population-based whole-brain functional directed network. This directed brain network exhibited prominent small-world properties, which obviously improved previous results of functional MRI studies showing weak small-world properties in the directed brain networks in terms of a kernel-based GCA and individual analysis. This brain network also showed significant modular structures associated with 5 well known subsystems: fronto-parietal, visual, paralimbic/limbic, subcortical and primary systems. Importantly, we identified several driving hubs predominantly located in the components of the attentional network (e.g., the inferior frontal gyrus, supplementary motor area, insula and fusiform gyrus) and several driven hubs predominantly located in the components of the default mode network (e.g., the precuneus, posterior cingulate gyrus, medial prefrontal cortex and inferior parietal lobule). Further split-half analyses indicated that our results were highly reproducible between two independent subgroups. The current study demonstrated the directions of spontaneous information flow and causal influences in the directed brain networks, thus providing new insights into our understanding of human brain functional connectome.     

Altered Neural Basis of the Reality Processing and Its Relation to Cognitive Insight in Schizophrenia

It has been reported that reality evaluation and recognition are impaired in patients with schizophrenia and these impairments are related to the severity of psychotic symptoms. The current study aimed to investigate the neural basis of impairments in reality evaluation and recognition and their relationships with cognitive insight in schizophrenia. During functional magnetic resonance imaging, 20 patients with schizophrenia and 20 healthy controls performed a set of reality evaluation and recognition tasks, in which subjects judged whether scenes in a series of drawings were real or unreal and whether they were familiar or novel. During reality evaluation, patients showed decreased activity in various regions including the inferior parietal lobule, retrosplenial cortex and parahippocampal gyrus, compared with controls. Particularly, parahippocampal gyrus activity was correlated with the severity of positive symptoms in patients. During recognition, patients also exhibited decreased activity in various regions, including the dorsolateral prefrontal cortex, inferior parietal lobule and posterior cingulate cortex. Particularly, inferior parietal lobule activity and posterior cingulate cortex activity were correlated with cognitive insight in patients. These findings provide evidence that neural impairments in reality evaluation and recognition are related to psychotic symptoms. Anomalous appraisal of context by dysfunctions in the context network may contribute to impairments in the reality processing in schizophrenia, and abnormal declarative memory processes may be involved in cognitive insight in patients with schizophrenia.     

Parietal and hippocampal contribution to topokinetic and topographic memory.

This paper reviews the involvement of the parietal cortex and the hippocampus in three kinds of spatial memory tasks which all require a memory of a previously experienced movement in space. The first task compared, by means of positron emission tomography (PET) scan techniques, the production, in darkness, of self-paced saccades (SAC) with the reproduction, in darkness, of a previously learned sequence of saccades to visual targets (SEQ). The results show that a bilateral increase of activity was seen in the depth of the intraparietal sulcus and the medial superior parietal cortex (superior parietal gyrus and precuneus) together with the frontal sulcus but only in the SEQ task, which involved memory of the previously seen targets and possibly also motor memory. The second task is the vestibular memory contingent task, which requires that the subject makes, in darkness, a saccade to the remembered position of a visual target after a passively imposed whole-body rotation. Deficits in this task, which involves vestibular memory, were found predominantly in patients with focal vascular lesions in the parieto-insular (vestibular) cortex, the supplementary motor area-supplementary eye field area, and the prefrontal cortex. The third task requires mental navigation from the memory of a previously learned route in a real environment (the city of Orsay in France). A PET scan study has revealed that when subjects were asked to remember visual landmarks there was a bilateral activation of the middle hippocampal regions, left inferior temporal gyrus, left hippocampal regions, precentral gyrus and posterior cingulate gyrus. If the subjects were asked to remember the route, and their movements along this route, bilateral activation of the dorsolateral cortex, posterior hippocampal areas, posterior cingulate gyrus, supplementary motor areas, right middle hippocampal areas, left precuneus, middle occipital gyrus, fusiform gyrus and lateral premotor area was found. Subtraction between the two conditions reduced the activated areas to the left hippocampus, precuneus and insula. These data suggest that the hippocampus and parietal cortex are both involved in the dynamic aspects of spatial memory, for which the name ''topokinetic memory'' is proposed. These dynamic aspects could both overlap and be different from those involved in the cartographic and static aspects of ''topographic'' memory.