Areas 3a, 3b, and 1 of human primary somatosensory cortex.

This study defines cytoarchitectonic areas 3a, 3b, and 1 of the human primary somatosensory cortex by objective delineation of cytoarchitectonic borders and ensuing cytoarchitectonic classification. This avoids subjective evaluation of microstructural differences which has so far been the only way to structurally define cortical areas. Ten brains were fixed in formalin or Bodian's fixative, embedded in paraffin, sectioned as a whole in the coronal plane at 20 microm, and cell stained. Cell bodies were segmented from the background by adaptive thresholding. Equidistant density profiles (125 microm wide, spacing 300 or 150 microm) were extracted perpendicularly to the pial surface across cortical layers II-VI and processed with multivariate statistical procedures. Positions of significant differences in shape between adjacent groups of profiles were correlated with the cytoarchitectonic pattern. Statistically significant borders can be reproduced at corresponding positions across a series of nearby sections. They match visible changes in cytoarchitecture in the cell-stained sections. Area 3a lies in the fundus of the central sulcus, and area 3b in the rostral bank of the postcentral gyrus. Area 1 lies on its crown and reaches down into the postcentral sulcus. Interareal borders, however, do not match macrostructural landmarks of the postcentral gyrus, and they considerably vary in their positions relative to these landmarks across different brains. Hence, only genuine microstructural analysis can define the borders between these cortical areas. Additional significant borders which do not correlate with visible changes in cytoarchitecture can be found within areas 3b and 1. They may represent somatotopy and/or cortical representations of different somatosensory receptors.     

Human somatosensory area 2: observer-independent cytoarchitectonic mapping, interindividual variability, and population map

We analyzed the topographical variability of human somatosensory area 2 in 10 postmortem brains. The brains were serially sectioned at 20 microm, and sections were stained for cell bodies. Area 2 was delineated with an observer-independent technique based on significant differences in the laminar densities of cell bodies. The sections were corrected with an MR scan of the same brain obtained before histological processing. Each brain's histological volume and representation of area 2 was subsequently reconstructed in 3-D. We found that the borders of area 2 are topographically variable. The rostral border lies between the convexity of the postcentral gyrus and some millimeters deep in the rostral wall of the postcentral sulcus. The caudal border lies between the fundus of the postcentral sulcus and some millimeters above it in the rostral wall. In contrast to Brodmann's map, area 2 does not extend onto the mesial cortical surface or into the intraparietal sulcus. When the postcentral sulcus is interrupted by a gyral bridge, area 2 crosses this bridge and is not separated into two segments. After cytoarchitectonic analysis, the histological volumes were warped to the reference brain of a computerized atlas and superimposed. A population map was generated in 3-D space, which describes how many brains have a representation of area 2 in a particular voxel. This microstructurally defined population map can be used to demonstrate activations of area 2 in functional imaging studies and therefore help to further understand the role of area 2 in somatosensory processing.     

Brodmann's areas 17 and 18 brought into stereotaxic space-where and how variable?

Studies on structural-functional associations in the visual system require precise information on the location and variability of Brodmann's areas 17 and 18. Usually, these studies are based on the Talairach atlas, which does not rely on cytoarchitectonic observations, but on comparisons of macroscopic features in the Talairach brain and Brodmann's drawing. In addition, in this atlas are found only the approximate positions of cytoarchitectonic areas and not the exact borders. We have cytoarchitectonically mapped both areas in 10 human brains and marked their borders in corresponding computerized images. Borders were defined on the basis of quantitative cytoarchitecture and multivariate statistics. In addition to borders of areas 17 and 18, subparcellations within both areas were found. The cytoarchitectonically defined areas were 3-D reconstructed and transferred into the stereotaxic space of the standard reference brain. Surface rendering of the brains revealed high individual variability in size and shape of the areas and in the relationship to the free surface and sulci. Ranges and centers of gravity of both areas were calculated in Talairach coordinates. The positions of areas 17 and 18 in the stereotaxic space differed between the hemispheres. Both areas reached significantly more caudal and medial positions on the left than on the right. Probability maps were created in which the degree of overlap in each stereotaxic position was quantified. These maps of areas 17 and 18 are the first of their kind and contain precise stereotaxic information on both interhemispheric and interindividual differences.     

Human primary auditory cortex: cytoarchitectonic subdivisions and mapping into a spatial reference system

The transverse temporal gyrus of Heschl contains the human auditory cortex. Several schematic maps of the cytoarchitectonic correlate of this functional entity are available, but they present partly conflicting data (number and position of borders of the primary auditory areas) and they do not enable reliable comparisons with functional imaging data in a common spatial reference system. In order to provide a 3-D data set of the precise position and extent of the human primary auditory cortex, its putative subdivisions, and its topographical intersubject variability, we performed a quantitative cytoarchitectonic analysis of 10 brains using a recently established technique for observer-independent definition of areal borders. Three areas, Te1.1, Te1.0, and Te1.2, with a well-developed layer IV, which represent the primary auditory cortex (Brodmann area 41), can be identified along the mediolateral axis of the Heschl gyrus. The cell density was significantly higher in Te1.1 compared to Te1.2 in the left but not in the right hemisphere. The cytoarchitectonically defined areal borders of the primary auditory cortex do not consistently match macroanatomic landmarks like gyral and sulcal borders. The three primary auditory areas of each postmortem brain were mapped to a spatial reference system which is based on a brain registered by in vivo magnetic resonance imaging. The integration of a sample of postmortem brains in a spatial reference system allows one to estimate the spatial variability of each cytoarchitectonically defined region with respect to this reference system. In future, the transfer of in vivo structural and functional data into the same spatial reference system will enable accurate comparisons of cytoarchitectonic maps of the primary auditory cortex with activation centers as established with functional imaging procedures.     

Reproducible activation in BA2, 1 and 3b associated with texture discrimination in healthy volunteers over time

We aimed to quantify specific location and reproducibility of brain activation associated with discrimination of a moving textured surface in adult healthy volunteers over a 6-month interval. A sensory stimulation device was developed to provide a texture stimulus to the fingertips at a controlled speed and pressure. Repeat measurements of regional cerebral blood flow, using positron emission tomography (PET), were obtained in 10 healthy individuals, aged 33 to 80 years (mean=55.8 years), at scanning sessions separated by 6 months. Stimulation and rest conditions were presented to either the right, dominant (n=5) or left non-dominant (n=5) hand. Activation location was objectively quantified with reference to probabilistic cytoarchitectonic maps. Differences in activation over time and regions of common activation were also quantified. Participants consistently activated Brodmann areas (BA) 2, 3b and 1, somatosensory areas of postcentral gyrus, at initial and 6-month studies: 93.1% of common activation for the right-hand (RH) and 60.6% for left-hand (LH) stimulation group were in these areas. Reproducible activation in BA6, 4a and 4p was also observed for the RH group (6.8% of common activation) and LH group (39.4%). There were no sites of significant difference over time for either hand. Highly consistent location of activation over time suggests that changes in loci of activation may be confidently monitored in adults using this paradigm. Use of probabilistic cytoarchitectonic maps permitted objective quantification of the anatomical location of the core of reproducible activation.     

Comparison of functional and cytoarchitectonic maps of human visual areas V1, V2, V3d,V3v,and V4(v)

Cytoarchitectonic maps of human striate and extrastriate visual cortex based upon post-mortem brains can be correlated with functionally defined cortical areas using, for example, fMRI. We here assess the correspondence of anatomical maps of the visual cortex with functionally defined in vivo visual areas using retinotopic mapping. To this end, anatomical maximum probability maps (aMPM) derived from individual cytoarchitectonic maps of striate and extrastriate visual areas were compared with functional localisers for the early visual areas. Using fMRI, we delineated dorsal and ventral human retinotopic areas V1, V2, and V3, as well as a quarter-field visual field representation lateral to V3v, V4(v), in 24 healthy subjects. Based on these individual definitions, a functional maximum probability map (fMPM) was then computed in analogy to the aMPM. Functional and anatomical MPMs were highly correlated at group level: 78.5% of activated voxels in the fMPM were correctly assigned by the aMPM. The group aMPM was less effective in predicting functional retinotopic areas in the individual brain due to the large inter-individual variability in the location and extent of visual areas (mean overlap 32–69%). We conclude that cytoarchitectonic maps of striate and extrastriate visual areas may provide a valuable method for assigning functional group activations and thus add valuable a priori knowledge to the analysis of functional imaging data of the visual cortex.     

一种基于人脑三维模型分割断面图像上脑沟、回的方法与实现

目的 借助人脑三维模型实现二维断面图像上大脑沟、回的分割。方法 首先在三维脑模型上以勾勒轮廓的方式界定不同脑沟、脑回区域,然后映射到断面相应区域上,进行区域内颜色填充,达到分割目的;并采用Visual C++ 6.0结合可视化类库工具包搭建脑沟、回分割平台,予以实现。结果 准确有效地分割出了序列断面图像上的右脑中央前回和中央后回。结论 此方法为获取完整、连续的脑沟、脑回断面解剖图谱提供了一种简单可行的实现手段,对于丰富数字化脑图谱及促进脑部功能与疾病诊断定位相关研究有重要意义。     

低频振幅结合功能连接对原发性甲亢患者感觉运动网络的功能MRI研究

目的采用低频振幅(amplitude of low frequency fluctuation,ALFF)与功能连接(functional connectivity,FC)相结合的方法,研究原发性甲状腺功能亢进患者静息状态下脑功能改变。材料与方法 12名未经治疗的甲亢患者为病例组,12名自愿接受扫描的健康人(年龄、性别无显著性差异)为对照组。采集所有被试静息态f MRI数据,采用REST及DPARSF软件分析原始数据,得出全脑ALFF,利用双样本t检验的方法比较病例组和对照组ALFF的变化,并以两组间ALFF值有显著性差异的脑区为感兴趣区(regions of interest,ROI)校正后行FC分析。结果与对照组相比,甲亢患者在双侧尾状核及双侧丘脑ALFF值降低(P0.001)。以上脑区的ALFF值均未发现与T3、T4有显著相关性(P0.05)。FC分析显示,左侧丘脑与双侧感觉运动区(包括中央前回、中央后回)FC增强(P0.001);右侧丘脑与右侧中央前回及中央后回连接增强(P0.001)。结论甲亢患者双侧丘脑的局部活动及其与大脑感觉运动网络的FC模式存在异常,增强的FC可能与代谢损伤所导致运动机能受损而使甲状腺功能异常患者有更强的功能需求有关。     

藏族双语者与汉族非双语者脑灰质VBM-MRI的初步研究

目的应用基于体素的形态学测量(voxel-based morphometry,VBM)技术初步探讨第二语言的习得对大脑微观结构的影响。材料与方法应用PHILIPS3.0 T磁共振对35名掌握藏-汉双语的健康藏族志愿者和35名汉族非双语健康志愿者行全脑扫描,获得T1-3D脑结构图像,然后应用VBM技术进行统计分析。结果藏族双语者较汉族左侧中央后回、左侧缘上回、左侧颞上回、右侧颞上回、右侧豆状核、右侧顶下小叶、左侧小脑8区脑灰质体积增加。结论第二语言的习得可以导致部分脑语言区体积的增加,双语学习可以促进脑语言区皮质的发育。     

EEG signatures of auditory activity correlate with simultaneously recorded fMRI responses in humans

We recorded auditory-evoked potentials (AEPs) during simultaneous, continuous fMRI and identified trial-to-trial correlations between the amplitude of electrophysiological responses, characterised in the time domain and the time–frequency domain, and the hemodynamic BOLD response. Cortical AEPs were recorded from 30 EEG channels within the 3 T MRI scanner with and without the collection of simultaneous BOLD fMRI. Focussing on the Cz (vertex) EEG response, single-trial AEP responses were measured from time-domain waveforms. Furthermore, a novel method was used to characterise the single-trial AEP response within three regions of interest in the time–frequency domain (TF-ROIs). The latency and amplitude values of the N1 and P2 AEP peaks during fMRI scanning were not significantly different from the Control session (p > 0.16). BOLD fMRI responses to the auditory stimulation were observed in bilateral secondary auditory cortices as well as in the right precentral and postcentral gyri, anterior cingulate cortex (ACC) and supplementary motor cortex (SMC). Significant single-trial correlations were observed with a voxel-wise analysis, between (1) the magnitude of the EEG TF-ROI1 (70–800 ms post-stimulus, 1–5 Hz) and the BOLD response in right primary (Heschl's gyrus) and secondary (STG, planum temporale) auditory cortex; and (2) the amplitude of the P2 peak and the BOLD response in left pre- and postcentral gyri, the ACC and SMC. No correlation was observed with single-trial N1 amplitude on a voxel-wise basis. An fMRI-ROI analysis of functionally-identified auditory responsive regions identified further single-trial correlations of BOLD and EEG responses. The TF amplitudes in TF-ROI1 and TF-ROI2 (20–400 ms post-stimulus, 5–15 Hz) were significantly correlated with the BOLD response in all bilateral auditory areas investigated (planum temporale, superior temporal gyrus and Heschl's gyrus). However the N1 and P2 peak amplitudes, occurring at similar latencies did not show a correlation in these regions. N1 and P2 peak amplitude did correlate with the BOLD response in bilateral precentral and postcentral gyri and the SMC. Additionally P2 and TF-ROI1 both correlated with the ACC. TF-ROI3 (400–900 ms post-stimulus, 4–10 Hz) correlations were only observed in the ACC and SMC. Across the group, the subject-mean N1 peak amplitude correlated with the BOLD response amplitude in the primary and secondary auditory cortices bilaterally, as well as the right precentral gyrus and SMC. We confirm that auditory-evoked EEG responses can be recorded during continuous and simultaneous fMRI. We have presented further evidence of an empirical single-trial coupling between the EEG and BOLD fMRI responses, and show that a time–frequency decomposition of EEG signals can yield additional BOLD fMRI correlates, predominantly in auditory cortices, beyond those found using the evoked response amplitude alone.     

The human inferior parietal cortex: cytoarchitectonic parcellation and interindividual variability

The inferior parietal cortex (IPC) integrates information from different sensory modalities and plays an important role in a variety of higher cognitive functions. Brodmann (Brodmann, K., 1909. Vergleichende Lokalisationslehre der Grosshirnrinde. Barth, Leipzig) proposed a cytoarchitectonic subdivision of the IPC into only two cortical areas, a rostral (BA 40) and a caudal (BA 39) area. Although his scheme was repeatedly challenged by other observers, it is still used for the anatomical localization of functional imaging data. The apparent differences between all these cyto- and myeloarchitectonic maps may be caused partly by the observer-dependent procedure of defining cytoarchitectonic borders by pure visual inspection of histological sections and partly by the interindividual variability of cytoarchitecture. The present observations and the resulting cortical map of the IPC are based on quantitative, observer-independent definitions of cytoarchitectonic borders and take into account each area's topographical variability across brains. Ten human postmortem brains were scanned using an MRI 3-D FLASH sequence prior to histological processing. After embedding in paraffin, serial sections through whole brains were prepared, and the sections were stained for cell bodies. Following high-resolution digitization of sections containing the IPC, we defined the cytoarchitecture and borders of each cortical area of this brain region using a multivariate statistical analysis of laminar cell density profiles. In contrast to previous observations, we found seven cytoarchitectonic areas in the IPC: five in the rostral (covering the region of BA 40) and two in the caudal part (covering the region of BA 39). We observed considerable interindividual variability in the topography of each area. A consistent correspondence between macroanatomical landmarks and cytoarchitectonic borders was not found. This new cytoarchitectonic map of the human IPC demonstrates regional differences in the cortical microstructure that is suggestive of functional differentiation. Furthermore, the map is registered in three dimensions and thereby provides a robust anatomical base for interpreting functional imaging studies.     

针刺合谷穴脑功能磁共振成像研究

目的观察针刺合谷穴引发脑内相关区域的变化情况.方法对6名健康右利手年轻被试进行右手合谷穴针刺,同时进行全脑fMRI,对脑内活动区域进行定位.结果针刺合谷时引起双侧感觉/运动区,额中回,颞上回前部,丘脑,额上内侧回,双侧小脑,双侧枕颞交界区,对侧岛叶,扣带回前部,中央后回上部以及同侧顶盖区激活,而降低的区域则分别表现在双侧颞极部,内颞叶区,额下内侧回,额叶眶部,双侧颞中回,双侧扣带回后部,枕叶,双侧中央前回中部,同侧中央前回上部.结论针刺合谷能够引发脑内相关区域的激活和降低,说明fMRI能够为针灸机制的探讨提供帮助.     

A new toolbox for combining magnetoencephalographic source analysis and cytoarchitectonic probabilistic data for anatomical classification of dynamic brain activity

Size and location of activated cortical areas are often identified in relation to their surrounding macro-anatomical landmarks such as gyri and sulci. The sulcal pattern, however, is highly variable. In addition, many cortical areas are not linked to well defined landmarks, which in turn do not have a fixed relationship to functional and cytoarchitectonic boundaries. Therefore, it is difficult to unambiguously attribute localized neuronal activity to the corresponding cortical areas in the living human brain. Here we present new methods that are implemented in a toolbox for the objective anatomical identification of neuromagnetic activity with respect to cortical areas. The toolbox enables the platform independent integration of many types of source analysis obtained from magnetoencephalography (MEG) together with probabilistic cytoarchitectonic maps obtained in postmortem brains. The probability maps provide information about the relative frequency of a given cortical area being located at a given position in the brain. In the new software, the neuromagnetic data are analyzed with respect to cytoarchitectonic maps that have been transformed to the individual subject brain space. A number of measures define the degree of overlap between and distance from the activated areas and the corresponding cytoarchitectonic maps. The implemented algorithms enable the investigator to quantify how much of the reconstructed current density can be attributed to distinct cortical areas. Dynamic correspondence patterns between the millisecond-resolved MEG data and the static cytoarchitectonic maps are obtained. We show examples for auditory and visual activation patterns. However, size and location of the postmortem brain areas as well as the inverse method applied to the neuromagnetic data bias the anatomical classification. Therefore, the adaptation to the respective application and a combination of the objective quantities are discussed.     

The somatosensory representation of the human clitoris: An fMRI study

We studied the central representation of pudendal afferents arising from the clitoral nerves in 15 healthy adult female subjects using electrical dorsal clitoral nerve stimulation and fMRI. As a control body region, we electrically stimulated the right hallux in eight subjects. In a block design experiment, we applied bilateral clitoral stimulation and unilateral (right) hallux stimulation. Activation maps were calculated for the contrasts ‘electrical dorsal clitoral nerve stimulation versus rest’ and ‘electrical hallux stimulation versus rest’.A random-effect group analysis for the clitoral stimulation showed significant activations bilateral in the superior and inferior frontal gyri, insulae and putamen and in the postcentral, precentral and inferior parietal gyri (including the primary and secondary somatosensory cortices). No activation was found on the mesial surface of the postcentral gyrus. For the hallux, activations occurred in a similar neuronal network but the activation in the primary somatosensory cortex was localized in the inter-hemispheric fissure.The results of this study demonstrate that the central representation of pudendal afferents arising from the clitoral nerves and sensory inputs from the hallux can be studied and distinguished from each other by fMRI. From the somatotopic order described in the somatosensory homunculus one would expect for electrical clitoral nerve stimulation activation of the mesial wall of the postcentral gyrus. In contrast, we found activations on the lateral surface of the postcentral gyrus.     

Construction of a 3D probabilistic atlas of human cortical structures

We describe the construction of a digital brain atlas composed of data from manually delineated MRI data. A total of 56 structures were labeled in MRI of 40 healthy, normal volunteers. This labeling was performed according to a set of protocols developed for this project. Pairs of raters were assigned to each structure and trained on the protocol for that structure. Each rater pair was tested for concordance on 6 of the 40 brains; once they had achieved reliability standards, they divided the task of delineating the remaining 34 brains. The data were then spatially normalized to well-known templates using 3 popular algorithms: AIR5.2.5's nonlinear warp (Woods et al., 1998) paired with the ICBM452 Warp 5 atlas (Rex et al., 2003), FSL's FLIRT (Smith et al., 2004) was paired with its own template, a skull-stripped version of the ICBM152 T1 average; and SPM5's unified segmentation method (Ashburner and Friston, 2005) was paired with its canonical brain, the whole head ICBM152 T1 average. We thus produced 3 variants of our atlas, where each was constructed from 40 representative samples of a data processing stream that one might use for analysis. For each normalization algorithm, the individual structure delineations were then resampled according to the computed transformations. We next computed averages at each voxel location to estimate the probability of that voxel belonging to each of the 56 structures. Each version of the atlas contains, for every voxel, probability densities for each region, thus providing a resource for automated probabilistic labeling of external data types registered into standard spaces; we also computed average intensity images and tissue density maps based on the three methods and target spaces. These atlases will serve as a resource for diverse applications including meta-analysis of functional and structural imaging data and other bioinformatics applications where display of arbitrary labels in probabilistically defined anatomic space will facilitate both knowledge-based development and visualization of findings from multiple disciplines.     

Age-associated changes of cerebral glucose metabolic activity in both male and female deaf children: parametric analysis using objective volume of interest and voxel-based mapping

Quantitative analysis of brain activity in the brains of children requires the establishment of age-associated norms. We investigated regional differences in age-associated changes in fluorodeoxyglucose (FDG) uptake in the developmental brains. From 87 (44 male and 43 female) deaf children from the age of 1 to 15, brain FDG positron emission tomography (PET) images were examined after spatial normalization, smoothing, and global normalization to identify brain regions showing a correlation between FDG uptake and age. Using population-based probabilistic volume of interests (VOIs), an objective VOI analysis was performed where normalized relative FDG uptake was measured and their correlations with age were examined in both genders. For the voxel-based analyses, the correlations with age were examined in a general linear model using statistical parametric mapping (SPM99). Both methods revealed that FDG uptake linearly increases with age both in the bilateral inferior prefrontal/orbitofrontal gyri and the right dorsomedial frontal gyrus and decreases in the inferior temporal gyrus and internal capsule white matter. Male children showed age-associated increases of FDG uptake in the right dorsomedial frontal gyrus, and female children in the left dorsolateral prefrontal cortex and thalamus. These changes in FDG uptake in various brain regions may suggest changes in synaptic density or regional activity resulting from normal maturation or deaf-induced adaptation. Caution should be exercised in interpreting the differences in the brain of child patients when compared with adult control's or with a different gender. Further research will be needed to examine if gender difference is manifested in the development rate of behavioral/cognitive functions in association with the age-associated changes of the right medial frontal (male) or the left dorsolateral prefrontal cortices.     

Pharmacokinetics and Distribution over the Blood-Brain Barrier of Zalcitabine (2′,3′-Dideoxycytidine) and BEA005 (2′,3′-Dideoxy-3′-Hydroxymethylcytidine) in Rats, Studied by Microdialysis

Microdialysis was applied to sample the unbound drug concentration in the extracellular fluid in brain and muscle of rats given zalcitabine (2′,3′-dideoxycytidine; n = 4) or BEA005 (2′,3′-dideoxy-3′-hydroxymethylcytidine; n = 4) (50 mg/kg of body weight given subcutaneously). Zalcitabine and BEA005 were analyzed by high-pressure liquid chromatography with UV detection. The maximum concentration of zalcitabine in the dialysate (C_max) was 31.4 ± 5.1 μM (mean ± standard error of the mean) for the brain and 238.3 ± 48.1 μM for muscle. The time to C_max was found to be from 30 to 45 min for the brain and from 15 to 30 min for muscle. Zalcitabine was eliminated from the brain and muscle with half-lives 1.28 ± 0.64 and 0.85 ± 0.13 h, respectively. The ratio of the area under the concentration-time curve (AUC) (from 0 to 180 min) for the brain and the AUC for muscle (AUC ratio) was 0.191 ± 0.037. The concentrations of BEA005 attained in the brain and muscle were lower than those of zalcitabine, with C_maxs of 5.7 ± 1.4 μM in the brain and 61.3 ± 12.0 μM in the muscle. The peak concentration in the brain was attained 50 to 70 min after injection, and that in muscle was achieved 30 to 50 min after injection. The half-lives of BEA005 in the brain and muscle were 5.51 ± 1.45 and 0.64 ± 0.06 h, respectively. The AUC ratio (from 0 to 180 min) between brain and muscle was 0.162 ± 0.026. The log octanol/water partition coefficients were found to be −1.19 ± 0.04 and −1.47 ± 0.01 for zalcitabine and BEA005, respectively. The degrees of plasma protein binding of zalcitabine (11% ± 4%) and BEA005 (18% ± 2%) were measured by microdialysis in vitro. The differences between zalcitabine and BEA005 with respect to the AUC ratio (P = 0.481), half-life in muscle (P = 0.279), and level of protein binding (P = 0.174) were not statistically significant. The differences were statistically significant in the case of the half-life in the brain (P = 0.032), clearance (P = 0.046), volume of distribution (P = 0.027) in muscle, and octanol/water partition coefficient (P = 0.019).     

Hemispheric shape of European and Japanese brains: 3-D MRI analysis of intersubject variability, ethnical, and gender differences

Hemispheric shape is studied using magnetic resonance imaging and 3-D reconstructions in right-handed, male and female, European and Japanese subjects. Japanese hemispheres are relatively shorter, but wider than European hemispheres. Regions of maximal intersubject variability in hemispheric shape are present in the occipital and temporal lobes in each sample. Deviations from this general pattern are found in the (i) right inferior parietal lobule (European hemispheres are more variable than Japanese), (ii) lower third of the pre- and postcentral gyri (female Japanese hemispheres are less variable than the other samples), (iii) right inferior frontal gyrus (male European hemispheres are more variable than the other samples), and (iv) polar part of the frontal lobe (female European hemispheres are less variable than the other samples). The distribution of intersubject variability between the hemispheres is less asymmetric in female than male brains. Male Japanese hemispheres are shorter but wider than female Japanese hemispheres, whereas European hemispheres show the inverse gender relations. These results demonstrate that hemispheric shape shows a considerable intersubject variability, which is not randomly distributed over the cortical surface but displays distinct regions of higher variability. Despite this intersubject variability significant interethnic- and gender-related differences in hemispheric shape are present, which may be relevant if individual brains have to be warped to a single or mean reference brain or realistic brain models are to be constructed.     

An optimized individual target brain in the Talairach coordinate system

The goal of regional spatial normalization is to remove anatomical differences between individual three-dimensional brain images by warping them to match features of a single target brain. Current target brains are either an average, suitable for low-resolution brain mapping studies, or a single brain. While a single high-resolution target brain is desirable to match anatomical detail, it can lead to bias in anatomical studies. An optimization method to reduce the individual anatomical bias of the ICBM high-resolution brain template (HRBT), a high-resolution MRI target brain image used in many laboratories, is presented. The HRBT was warped to all images in a group of 27 normal subjects. Displacement fields were averaged to calculate the "minimal deformation target" (MDT) transformation for optimization. The greatest anatomical changes in the HRBT, following optimization, were observed in the superior precentral and postcentral gyri on the right, the right inferior occipital, the right posterior temporal lobes, and the lateral ventricles. Compared with the original HRBT, the optimized HRBT showed better anatomical matching to the group of 27 brains. This was quantified by the improvements in spatial cross-correlation and between the group of brains and the optimized HRBT (P < 0.05). An intended use of this processing is to create a digital volumetric atlas that represents anatomy of a normal adult brain by optimizing the HRBT to the group consisting of 100+ normal subjects.     

观察精神发育迟缓患者的脑局部一致性

目的 通过比较精神发育迟缓(MR)患者与正常人之间脑局部一致性(ReHo)的差异,观察MR患者静息状态下局部脑活动变化。方法 利用3.0T 磁共振扫描仪对10例MR患者(MR组)及25名健康志愿者(正常对照组)行静息态fMRI。采用SPM8和REST软件进行数据处理,获得两组之间ReHo值存在显著差异的脑区。结果 与正常对照组相比,MR组左额中回、额下回、颞上回和岛叶、右中扣带回、后扣带回、缘上回和顶下小叶ReHo值显著减低,左枕中回和楔叶、右枕中回、楔叶和舌回、右楔前叶、左中央前回和中央后回ReHo值显著增高。结论 静息状态下,MR患者高级脑功能区局部活动减弱可能是智力低下的神经基础;而初级脑功能区局部活动增强可能反映了补偿性效应。