Cortisol responses of healthy volunteers undergoing magnetic resonance imaging

Self-reported anxiety is associated with various medical procedures, including structural and functional magnetic resonance imaging (MRI). The present study tested the hypothesis that MRI scanning would be associated with elevated cortisol levels in participants with no prior scanning experience. Baseline and post-scan cortisol levels, as well as measures of state and trait anxiety, were obtained from scanner-naive (n = 6) and scanner-experienced (n = 8) research participants. The anxiety scores and cortisol responses of the scanner-naive and scanner-experienced participants were compared. Subjects novel to MRI were no more anxious before the scan than were subjects familiar with the MRI examination, but the scanner-naive subjects manifested heightened post-scan cortisol secretion when compared to their pre-scan level and when compared to the scanner-experienced participants. The results are consistent with the hypothesis that the scanning environment can induce cortisol elevations and are congruent with the well-established effects of acute stressors on activity of the hypothalamic-pituitary-adrenal (HPA) axis. The implications for neuroimaging studies are discussed.     

Tolbutamide blocks postsynaptic but not presynaptic effects of adenosine on hippocampal CA1 neurones

Summary. Extracellular recording in the CA1 pyramidal cell layer of rat hippocampal slices was used to examine the effect of the ATP-sensitive potassium channel blocker tolbutamide and the channel opener levcromakalim on responses to adenosine. Tolbutamide 1 mM blocked the inhibitory effect of adenosine on the size of orthodromic population spikes but had no effect on the inhibitory action of adenosine on field EPSPs. Tolbutamide also blocked the suppression by adenosine of repetitive antidromic spikes induced in calcium-free media with high magnesium but did not prevent the effects of baclofen. Levcromakalim 100 μM potentiated inhibitory effect of adenosine, but not baclofen, on orthodromic population spikes. The results show that at postsynaptic, but not presynaptic, sites adenosine may activate an ATP-sensitive potassium channel. Accepted December 15, 1997; received September 9, 1997     

Cerebrovascular abnormalities in pediatric stroke: assessment using parenchymal and angiographic magnetic resonance imaging

Three-dimensional (volume) magnetic resonance angiography is a noninvasive technique that images the intracranial and cervical arterial vasculature without contrast agents. Twenty-four children with strokes had combined parenchymal magnetic resonance imaging and magnetic resonance angiography 1 day to 4 years after acute presentation. Eight had had prior intra-arterial angiography. Eighteen magnetic resonance angiographic studies showed arterial stenosis or occlusion in the vascular distribution of magnetic resonance image-defined brain infarction and, in 7 children, in the same location as previously defined abnormalities on intra-arterial angiography. One child had a normal intra-arterial angiogram and magnetic resonance angiogram. The other 5 children with normal magnetic resonance angiographic studies included 3 with presumed embolic disease, 1 with meningitis, and 1 with Crohn's disease-related vasculitis. Collateral flow patterns could be determined in 4 children. Artifact presenting as filling defects in vessels was present in 10 studies, but did not interfere with interpretation of 8 studies. Combined magnetic resonance imaging/magnetic resonance angiography provides a screening technique to evaluate noninvasively brain parenchyma and vasculature in children with suspected large-vessel abnormalities, allowing selection for intra-arterial angiography and serial monitoring of vascular abnormalities over time and during therapeutic intervention.     

Visual hallucinations in schizophrenia investigated with functional magnetic resonance imaging

We investigated a 27-year old patient with paranoid schizophrenia. Brain activity related to visual hallucinations was found in higher visual areas corresponding to the content of the hallucinations (faces, bodies, scenes) and the hippocampus. We assume that the hippocampal activity is related to the retrieval of visual images from memory and that sensory cortex activity is related to the vividness of the perceptual experience.     

联想学习记忆的脑功能磁共振成像

目的 通过脑功能磁共振成像(functional magnetic resonance imaging,fMRI)技术检测健康人脑纹状体边缘区(marginal division of the striatum,MrD)是否参与联想学习记忆的过程.方法 对16名右利手健康志愿者进行一项配对词语联想学习记忆任务的同时,进行fMRI扫描.试验采用组块设计并选用SPM 99软件进行数据分析和脑功能区定位.结果 应用单样本t检验(SPM统计软件将体素的激活强度T值在数值上等于t检验的t值),当统计阈值设为P＜0.005时,左枕叶和左额上、中回在任务编码时被显著激活(最大激活强度分别为T=13.87、9.36),左纹状体边缘区也在该阶段被明显激活(T=5.46);而左顶叶则在记忆提取阶段被显著激活(T=8.73).结论 除皮质外,皮质下结构如MrD也参与了词语联想学习记忆过程.     

正常人词语流畅性作业的脑功能磁共振成像研究

目的 利用功能磁共振成像(fMRI)技术探讨词语流畅性作业的脑功能定位。方法对18名健康志愿者进行词语流畅性作业的fMRI检查,fMRI用梯度回波-平面回波成像序列采集数据,经工作站处理后获功能图像。结果 经Fisher精确检验法,健康志愿者的双侧额上回、双侧额中回、右侧额下回及右侧扣带回的激活脑区计数,与理想激活脑区计数的差异均无显著性(P>0.05),其余脑区激活计数的差异均有显著性(P<0.05)。结论 双侧额叶背外侧及右侧额叶腹外侧可能参与长时记忆的提取过程,其中额叶背外侧可能参与核查及管理工作,而额叶腹外侧可能参与搜寻特异目标的过程。     

健康者三叉神经磁共振扩散张量成像研究

目的 测量三叉神经桥池段的表观扩散系数(ADC)值和部分各向异性分数(FA)值,了解三叉神经桥池段各参数的特点。 方法 选择50例健康志愿者三叉神经桥池段距离脑干发出点0mm、3mm、6mm、9mm共四处,利用DTI图像与B-TFE或THRIVE图像融合成像,提高三叉神经桥池段显示的空间分辨率,并利用该图像测量并分别记录ADC值与FA值,对所有受检者行三叉神经桥池段追踪成像。 结果 受检者左侧与右侧三叉神经桥池段的ADC值和FA值差异均无统计学意义(P＞0.05)。越靠近脑干发出点,左右两侧三叉神经桥池段的各导出量越呈现左右不对称的趋势。双侧三叉神经桥池段距脑干不同距离各位置的DTI导出量分析发现：相邻两距离间ADC值差异均有统计学意义(P＜0.05),出脑干后随距离增加ADC值逐渐升高,但行至6～9 mm间突然回转下降;FA值在0～6 mm间随距离增加而逐渐降低,且相邻两距离间差异均有统计学意义(P＜0.05),但行至6～9 mm间FA值不再有明显变化。 结论 DTI图像能够清晰分辨双侧三叉神经桥池段,可实现DTI各项导出量的测量。随着距脑干发出点距离的不同,各导出量发生有规律的变化,预示着DTI在明确区分三叉神经的中枢神经系统段、过渡段和周围神经系统段以及检出颅神经血管压迫方面的应用前景。     

功能磁共振成像研究睡眠剥夺36小时对健康男性工作记忆的影响

目的 利用功能磁共振成像(functional magnetic resonance imaging,fMRI)技术研究睡眠剥夺36 h对健康男性工作记忆的影响及可能机制.方法 10名健康男性受试者连续36 h睡眠剥夺,睡眠剥夺前后分别接受工作记忆任务测试,同时进行fMRI扫描.fMRI扫描采用2项工作记忆任务,收集获得的行为学结果和fMRI图像,用SPM2软件进行图像分析.比较睡眠剥夺前后工作记忆任务测试及fMRI扫描结果.结果 剥夺后LTR任务的反应时间为(866±102)ms,比剥夺前[(754±91)ms]明显延长(t=2.59,P<0.01),准确率为84.78%±8.71%,比剥夺前(95.31%±3.56%)明显降低(t=3.52,P<0.01);剥夺后PLUS任务的反应时间为(848±94)ms,比剥夺前[(756±79),ms]明显延长(t=2.37,P<0.05),准确率为84.22%±9.66%,比剥夺前(95.70%±4.72%)明显降低(t=3.38,P<0.01);剥夺前在额顶叶、前扣带回和丘脑等工作记忆相关性脑区被激活.PLUS任务较LTR任务激活脑区范围更广,强度更显著.剥夺后顶叶激活降低,前额叶和丘脑的激活增强.结论 睡眠剥夺能够导致工作记忆能力受损.fMRI显示睡眠剥夺后完成工作记忆任务时,在相应脑区顶叶激活降低,前额叶和丘脑激活增强,这可能是睡眠剥夺导致认知功能损害的机制之一.     

Protocol for volumetric segmentation of medial temporal structures using high-resolution 3-D magnetic resonance imaging

Quantitative analysis of brain structures in normal subjects and in different neurological conditions can be carried out in vivo through magnetic resonance imaging (MRI) volumetric studies. The use of high-resolution MRI combined with image post-processing that allows simultaneous multiplanar view may facilitate volumetric segmentation of temporal lobe structures. We define a protocol for volumetric studies of medial temporal lobe structures using high-resolution MR images and we studied 30 healthy subjects (19 women; mean age, 33 years; age range, 21-55 years). Images underwent field non-homogeneity correction and linear stereotaxic transformation into a standard space. Structures of interest comprised temporopolar, entorhinal, perirhinal, parahippocampal cortices, hippocampus, and the amygdala. Segmentation was carried out with multiplanar assessment. There was no statistically significant left/right-sided asymmetry concerning any structure analyzed. Neither gender nor age influenced the volumes obtained. The coefficient of repeatability showed no significant difference of intra- and interobserver measurements. Imaging post-processing and simultaneous multiplanar view of high-resolution MRI facilitates volumetric assessment of the medial portion of the temporal lobe with strict adherence to anatomic landmarks. This protocol shows no significant inter- and intraobserver variations and thus is reliable for longitudinal studies.     

颈动脉粥样硬化斑块无创性高分辨力磁共振成像研究进展

颈动脉粥样硬化性狭窄与脑卒中复发密切相关。目前颈动脉狭窄的治疗方法主要包括药物治疗和外科手术(颈动脉支架成形术和颈动脉内膜切除术)。脑卒中预防在于识别颈动脉狭窄危险因素,筛查脑卒中复发高危患者,从而使其从药物治疗或外科手术中获益,然而目前仅根据颈动脉狭窄程度制定治疗方案,缺乏个体化治疗。近年来,新型影像学技术如无创性高分辨力磁共振成像(HRMRI)等,可以检测出颈动脉易损斑块。与传统数字减影血管造影术测量的颈动脉狭窄程度相比,无创性HRMRI可以根据颈动脉斑块特征准确预测同侧脑卒中风险,从而指导个体化治疗。     

Ex vivo high-resolution magnetic resonance imaging of the brain in Joubert's syndrome

This study employs ex vivo high-resolution magnetic resonance imaging (MRI) to examine anatomic structures in an intact brain of a child with Joubert's syndrome. Several of the specific hindbrain malformations associated with Joubert's syndrome are well resolved with ex vivo MRI, including the "molar tooth sign," which arises from enlarged and maloriented superior cerebellar peduncles, hypoplastic vermis, and deepening of the interpeduncular fossa. Superior resolution was achieved compared with that of in vivo MRI and included visualization of the inferior olives. One high-resolution study also showed that the decreased width of the brainstem isthmus is probably caused by failure of superior cerebellar peduncles to cross the midline at that level. The results of this study suggest that high-resolution MRI may be useful in screening the brainstem for malformations that can be studied histologically in a much more targeted fashion.     

An integrative multivariate approach for predicting functional recovery using magnetic resonance imaging parameters in a translational pig ischemic stroke model

Magnetic resonance imaging(MRI) is a clinically relevant, real-time imaging modality that is frequently utilized to assess stroke type and severity. However, specific MRI biomarkers that can be used to predict long-term functional recovery are still a critical need. Consequently, the present study sought to examine the prognostic value of commonly utilized MRI parameters to predict functional outcomes in a porcine model of ischemic stroke. Stroke was induced via permanent middle cerebral artery occlusion. At 24 hours post-stroke, MRI analysis revealed focal ischemic lesions, decreased diffusivity, hemispheric swelling, and white matter degradation. Functional deficits including behavioral abnormalities in open field and novel object exploration as well as spatiotemporal gait impairments were observed at 4 weeks post-stroke. Gaussian graphical models identified specific MRI outputs and functional recovery variables, including white matter integrity and gait performance, that exhibited strong conditional dependencies. Canonical correlation analysis revealed a prognostic relationship between lesion volume and white matter integrity and novel object exploration and gait performance. Consequently, these analyses may also have the potential of predicting patient recovery at chronic time points as pigs and humans share many anatomical similarities(e.g., white matter composition) that have proven to be critical in ischemic stroke pathophysiology. The study was approved by the University of Georgia(UGA) Institutional Animal Care and Use Committee(IACUC; Protocol Number: A2014-07-021-Y3-A11 and 2018-01-029-Y1-A5) on November 22, 2017.     

高分辨磁共振成像在脑桥旁正中梗死患者中的诊断价值

目的 探讨高分辨磁共振成像(high resolution magnetic resonance imaging, HRMRI)在脑桥旁正中梗死(paramedian pontine infarction,PPI)患者中的诊断价值。方法 连续收集经磁共振证实的PPI患者32例,全部行磁共振血管成像(magnetic resonance angiography, MRA)和HRMRI检查,利用HRMRI分析动脉粥样硬化斑块在基底动脉(basilar artery, BA)的分布位置,比较MRA与HRMRI识别BA狭窄能力的差异。结果 MRA检查显示BA狭窄者11例(34.4%),HRMRI 显示BA狭窄者27例(84.4%)(P<0.01)。HRMRI显示BA狭窄的27例患者,其粥样硬化斑块位于梗死病灶同侧25例(92.6%)、对侧2例(7.4%)。结论 HRMRI在诊断BA狭窄方面可信度较高; 脑桥旁正中梗死患者BA粥样硬化斑块大多分布在梗死病灶同侧     

Quantification of lateral ventricular subdivisions in schizophrenia by high-resolution three-dimensional magnetic resonance imaging

In vivo brain imaging and postmortem investigations have demonstrated ventricular enlargement in the brains of schizophrenic patients. However, the extent of changes in the volume of discrete ventricle subdivisions has not been clearly established. We conducted high-resolution three-dimensional magnetic resonance imaging in 40 schizophrenic patients (20 males and 20 females) and 40 healthy volunteers (20 males and 20 females). The lateral ventricle in each hemisphere was divided into the anterior horn, body, posterior horn and temporal horn. The volumes of the hemispheres, four subdivisions of the lateral ventricles and the third ventricle were measured. Compared to the control subjects, the bilateral hemisphere volumes were significantly lower in the patients than in the control subjects. In the lateral ventricular subdivisions of the male patients, the most substantial volume increase was in the left temporal horn, and volume increases were also observed in the bilateral anterior horns and the right body. The male patients also had a significantly increased volume of the third ventricle. The female patients showed similar patterns with less statistical significance. Thus, the schizophrenia patients showed ventricular enlargement, particularly in the left temporal horn, being more severely affected in the male than in the female.     

Lithium effects on brain glutamatergic and GABAergic systems of healthy volunteers as measured by proton magnetic resonance spectroscopy

Lithium is a first-line medicinal treatment for acute bipolar disorder and is also used prophylactically in manic depressive illnesses; however, its mechanism of action is still largely unknown. Animal and human studies have suggested that lithium modulates glutamatergic and GABAergic neurotransmissions. The aim of this study is to investigate the effects of lithium on brain glutamate (Glu), glutamine (Gln), and gamma-aminobutyric acid (GABA) levels in healthy individuals using proton magnetic resonance spectroscopy (1H-MRS). In vivo 3 Tesla 1H-MRS was performed on the anterior cingulate cortex and bilateral basal ganglia initially and after two weeks of lithium administration on 8 healthy male subjects who had a mean age of 34.9 years. After two weeks of lithium administration, Gln significantly decreased in the left basal ganglia and showed a decreasing trend in the right basal ganglia. Additionally, Glu+Gln (Glx) significantly decreased in the right basal ganglia and showed a decreasing trend in the left basal ganglia. Glu did not significantly change in any of the three tested areas, and GABA exhibited no significant change after the lithium administration when measured in the anterior cingulate cortex and left basal ganglia. This study is the first to demonstrate that subchronic lithium treatment decreases Gln and Glx levels in the bilateral basal ganglia of healthy individuals. Our finding might suggest that the decrease of Glx levels is associated with the pharmacological actions of subchronic lithium treatment.     

Source localization of the N400 response in a sentence-reading paradigm using evoked magnetic fields and magnetic resonance imaging

The aim of the present investigation was to localize the sources of the N400 response elicited in a sentence-reading paradigm. Eight neurologically healthy adults viewed sentences that were presented one word at a time in the center of a computer screen. Half of the sentences ended with a semantically inappropriate word, while the other half had appropriate endings. Event-related potentials recorded at Fz and Pz showed a negative-going deflection, the amplitude of which was strongly affected by semantic congruity (N400). Evoked magnetic fields that were simultaneously recorded over the left hemisphere showed clear magnetic field extrema in seven subjects during the time course of the N400. Underlying sources were successfully modeled as single equivalent current dipoles. Anatomical regions that contained the dipoles were localized by superimposing dipole coordinates onto magnetic resonance scans. Dipole regions were found in temporal lobe structures, in the vicinity of the hippocampus and the parahippocampal gyrus (in two subjects) and in posterior temporal neocortical regions (in the vicinity of the middle temporal gyrus; in five subjects). These findings are consistent with the view that posterior association cortices in the left hemisphere are involved in word recognition and semantic comprehension during reading.     

Brain functional connectivity during storage based on resting state functional magnetic resonance imaging with synchronous urodynamic testing in healthy volunteers

Brain Imaging and Behavior - The aim of the study was to elucidate the correlation between spatially distinct brain areas with a full bladder from the perspective of functional connectivity using...     

Volumetric structural magnetic resonance imaging (MRI) of the rat hippocampus following kainic acid (KA) treatment

An in vivo MRI study employing a high field (7T) magnet and a T1- and T2-weighted imaging sequence with subsequent histopathological evaluations was undertaken to develop and evaluate MRI-based volumetric measurements in the rat. The brain structures considered were the hippocampus, the cingulate cortex, the retrosplenial granular cortex and the ventricles. Control (n=3) and kainic acid (KA; n=4) treated rats were scanned 10 days following the manifestation of stage four seizures. The MRI images exhibited anatomical details (125 microm in-plane resolution) that enabled volumetric analysis with high intra-rater reliability. Volumetric analysis revealed that KA-treated rats had significantly smaller hippocampi, and a significant increase in ventricular size. The cingulate cortex and the retrosplenial granular cortex did not differ in volume between the two groups. The histological observations supported the MRI data showing neuronal loss and neuronal degeneration in CA1 and CA3 of the hippocampus, which was accompanied by strong microglia activation. These data demonstrate a reliable and valid method for the measurement of the rat hippocampus in vivo using MRI with a high field magnet, thereby providing a useful tool for future studies of rodent models of neuro-degenerative diseases.