High-resolution Structural MR Images Research Articles

Divergent effects of sex on hippocampal subfield alterations in drug-naive patients with major depressive disorder

BackgroundThe hippocampus is a crucial brain structure in etiological models of major depressive disorder (MDD). It remains unclear whether sex differences in the incidence and symptoms of MDD are related to differential illness-associated brain alterations, including alterations in the hippocampus. This study investigated divergent the effects of sex on hippocampal subfield alterations in drug-naive patients with MDD. MethodsHigh-resolution structural MR images were obtained from 144 drug-naive individuals with MDD early in their illness course and 135 age- and sex-matched healthy controls (HCs). Hippocampal subfields were segmented using FreeSurfer software and analyzed in terms of both histological subfields (CA1–4, dentate gyrus, etc.) and more integrative larger functional subregions (head, body and tail). ResultsWe observed a significant overall reduction in hippocampal volume in MDD patients, with deficits more prominent deficits in the posterior hippocampus. Differences in anatomic alterations between male and female patients were observed in the CA1-head, presubiculum-body and fimbria in the left hemisphere. Exploratory analyses revealed different patterns of clinical and memory function correlations with histological subfields and functional subregions between male and female patients primarily in the hippocampal head and body. LimitationsThis cross-sectional study cannot clarify the causality of hippocampal alterations or their association with illness risk or onset. ConclusionsThese findings represent the first reported sex-specific alterations in hippocampal histological subfields in patients with MDD early in the illness course prior to treatment. Sex-specific hippocampal alterations may contribute to diverse sex differences in the clinical presentation of MDD.

FV 13 A human in vivo atlas template of the inner ear derived from high-resolution multi-modal structural MR imaging

FV 13 A human in vivo atlas template of the inner ear derived from high-resolution multi-modal structural MR imaging

FV 12 Longitudinal study on hippocampal volume and neuropsychological outcome in IgM-NMDAR-antibody-associated encephalopathy

Introduction Anti-NMDAR-IgM-autoantibodies (IgM-NMDAR-aab) are occurring in approximately 4–5% of the general population ( Dahm et al., 2014 ). IgM-NMDAR-aab are also associated to a rare encephalopathy presenting with symptoms resembling fronto-temporal dementia (FTD) but with much faster progression as a neurodegenerative disease ( Doss et al., 2014 ). Treatment with an immunosuppressive therapy is recommend but has not been evaluated with neuroimaging and neuropsychology. Here, we present longitudinal data on two cases. Methods We identified two patients referred to us presenting memory disturbances and memory loss together with a severe executive dysfunction and alteration in behavior developing within 3–5 months. CSF did not reveal an Alzheimer’s-disease like constellation. Routine MRI scans were considered normal. Neuropsychological testing showed severe deficits in fronto-temporal functioning. Antibody screening via indirect immunofluorescence test (IFT) involved IgM-, IgA- and IgG-NMDAR-ab, Lgi-1-, CASPR2-, DPPX- and AMPA-IgG-ab and also onconeuronal ab via an immunoblot analysis (anti-Hu, -Yo, -Ri, -CV2, -Ma2, -Amphiphysin, -GAD65, -Tr(DNER), -Sox1, -Titin and -Recoverin-ab; all tests were performed by Euroimmun, Lubeck, Germany). Both patients received multiple methylprednisolone (MP) i.v. therapies (each cycle with 1 g i.v. per day for 3 days for a total of 9 g MP(Pat1) or 15 g MP(Pat2)). MRI scans were conducted during therapy and after therapy. Data were acquired on a 3-Tesla MR scanner (Siemens MAGNETOM Prisma, Erlangen, Germany) equipped with a 20-channel head coil. T1-weighted, high-resolution structural MR-images were obtained using a three dimensional MPRAGE sequence yielding an isotropic resolution of 1 mm 3 . Hippocampal volume was manually assessed via Multitracer software (free software, UCLA, USA) and double-checked. Neuropsychological assessment was identically performed for each patient during each assessment time point (Rey-Figure, Trail making test A/B, executive and memory test, digit and word-span). Results Serum titers were highly pathological for path patients, with Pat1 having an IgM-NMDAR-aab titer of 1:160 and Pat2 of 1:320. No other abs were detected via immunoblot or IFT. In addition, results of manual assessment revealed that hippocampal (HC) volume increased bilaterally in Pat1 due to MP-treatment. Accordingly, neuropsychological measures of memory function (digit span, Rey-figure) improved slightly in Pat1. In Pat2, in contrast, only the right HC had a slight volume increase, while the left HC volume showed a slight decrease. Nevertheless, initial memory dysfunctions observed in Pat2 declined remarkably in the course of our treatment. Beyond that, clinical assessment showed an overall improvement in Pat1 and in Pat2 a complete recovery after intravenous MP-treatment. Discussion Here, we show the first longitudinal follow-up of NMDA-aab associated encephalopathy. Treatment with MP resulted in a good to excellent improvement of clinical as well as neuropsychological assessment. These functional measures, however, were only partially mirrored by HC volume alterations during the course of the treatment. In cases of unclear dementia-like symptoms NMDAR-aab associated encephalopathy should be taken into account and treated with immunosuppressives.

基于表面的形态测量学：3T与7T高分辨磁共振结构成像受试者内比较

ObjectiveHigh resolution structural MR imaging can reveal structural characteristics of cerebral cortex and provide an insight into normal brain development and neuropsychological diseases. The aim of this study was to compare cortical structural characteristics of normal human brain between 3T and 7T MRI systems using surface-based morphometry based on high resolution structural MR imaging. Methods Twelve healthy volunteers were scanned by both 3T with 3D T1-weighted fast spoiled gradient recalled echo (3D T1-FSPGR) sequence and 7T with 3D T1-weighted magnetization-prepared rapid gradient echo (3D T1-MPRAGE) sequence. MRI data were processed with FreeSurfer. The cortical thickness, white and gray matter surface area, convexity, and curvature from data of 3T and 7T were measured and compared by paired t-test. Results Measurements of mean cortical thickness, total white matter surface area and gray matter surface area of 3T were larger than those of 7T (left hemisphere: P=0.000, 0.006, 0.020 respectively; right hemisphere: P=0.000, 0.000, 0.000 respectively). Surface-based morphometry over the whole brain demonstrated both reduced and increased measurements of cortical thickness, white and gray surface area, convexity, and curvature at 7T compared to 3T. Conclusions Inconsistency of brain structural attribute between 3T and 7T was confirmed, and researchers should be cautious about data when using ultrahigh field MR system to investigate brain structural changes.

Sensory migraine aura is not associated with structural grey matter abnormalities.

Migraine with aura (MA) is characterized by cortical dysfunction. Frequent aura attacks may alter cerebral cortical structure in patients, or structural grey matter abnormalities may predispose MA patients to aura attacks. In the present study we aimed to investigate cerebral grey matter structure in a large group of MA patients with and without sensory aura (i.e. gradually developing, transient unilateral sensory disturbances). We included 60 patients suffering from migraine with typical visual aura and 60 individually age and sex-matched controls. Twenty-nine of the patients additionally experienced sensory aura regularly. We analysed high-resolution structural MR images using two complimentary approaches and compared patients with and without sensory aura. Patients were also compared to controls. We found no differences of grey matter density or cortical thickness between patients with and without sensory aura and no differences for the cortical visual areas between patients and controls. The somatosensory cortex was thinner in patients (1.92 mm vs. 1.96 mm, P = 0.043) and the anterior cingulate cortex of patients had a decreased grey matter density (P = 0.039) compared to controls. These differences were not correlated to the clinical characteristics. Our results suggest that sensory migraine aura is not associated with altered grey matter structure and that patients with visual aura have normal cortical structure of areas involved in visual processing. The observed decreased grey matter volume of the cingulate gyrus in patients compared to controls have previously been reported in migraine with and without aura, but also in a wide range of other neurologic and psychiatric disorders. Most likely, this finding reflects general bias between patients and healthy controls.

Gray Matter Volume Reduction Is Associated with Cognitive Impairment in Neuromyelitis Optica.

Whether gray matter impairment occurs in neuromyelitis optica is a matter of ongoing debate, and the association of gray matter impairment with cognitive deficits remains largely unknown. The purpose of this study was to investigate gray matter volume reductions and their association with cognitive decline in patients with neuromyelitis optica. This study included 50 patients with neuromyelitis optica and 50 sex-, age-, handedness-, and education-matched healthy subjects who underwent high-resolution structural MR imaging examinations and a battery of cognitive assessments. Gray matter volume and cognitive differences were compared between the 2 groups. The correlations of the regional gray matter volume with cognitive scores and clinical variables were explored in the patients with neuromyelitis optica. Compared with healthy controls (635.9 ± 51.18 mL), patients with neuromyelitis optica (602.8 ± 51.03 mL) had a 5.21% decrease in the mean gray matter volume of the whole brain (P < .001). The significant gray matter volume reduction in neuromyelitis optica affected the frontal and temporal cortices and the right thalamus (false discovery rate correction, P < .05). The regional gray matter volumes in the frontal and temporal cortices were negatively correlated with disease severity in patients with neuromyelitis optica (Alphasim correction, P < .05). Patients with neuromyelitis optica had impairments in memory, information processing speed, and verbal fluency (P < .05), which were correlated with gray matter volume reductions in the medial prefrontal cortex and thalamus (Alphasim correction, P < .05). Gray matter volume reduction is present in patients with neuromyelitis optica and is associated with cognitive impairment and disease severity in this group.

Cortical thinning in former professional soccer players.

Soccer is the most popular sport in the world. Soccer players are at high risk for repetitive subconcussive head impact when heading the ball. Whether this leads to long-term alterations of the brain's structure associated with cognitive decline remains unknown. The aim of this study was to evaluate cortical thickness in former professional soccer players using high-resolution structural MR imaging. Fifteen former male professional soccer players (mean age 49.3 [SD 5.1] years) underwent high-resolution structural 3T MR imaging, as well as cognitive testing. Fifteen male, age-matched former professional non-contact sport athletes (mean age 49.6 [SD 6.4] years) served as controls. Group analyses of cortical thickness were performed using voxel-based statistics. Soccer players demonstrated greater cortical thinning with increasing age compared to controls in the right inferolateral-parietal, temporal, and occipital cortex. Cortical thinning was associated with lower cognitive performance as well as with estimated exposure to repetitive subconcussive head impact. Neurocognitive evaluation revealed decreased memory performance in the soccer players compared to controls. The association of cortical thinning and decreased cognitive performance, as well as exposure to repetitive subconcussive head impact, further supports the hypothesis that repetitive subconcussive head impact may play a role in early cognitive decline in soccer players. Future studies are needed to elucidate the time course of changes in cortical thickness as well as their association with impaired cognitive function and possible underlying neurodegenerative process.

Cortical thinness and volume differences associated with marijuana abuse in emerging adults

BackgroundThe prevalence of marijuana (MJ) use among youth and its legalization for medical or recreational use has intensified public health endeavors of understanding MJ effects on brain structure and function. Studies indicate that MJ use is related to impaired cognitive performance, and altered functional brain activation and chemistry in adolescents and adults, but MJ effects on brain morphology in emerging adults are less understood. MethodsFifteen MJ users (age 21.8±3.6, 2 females) and 15 non-user (NU) participants (age 22.3±3.5, 2 females) were included, demographically matched on age, education and alcohol use. High-resolution structural MR images were acquired at 3Tesla. Cortical thickness (CT) and volumetric analyses were performed using Freesurfer. A priori regions of interest (ROI) included orbitofrontal and cingulate cortices, amygdala, hippocampus and thalamus. ResultsWhole brain CT analysis did not result in significant group differences in a priori ROIs but revealed MJ users had significantly less CT (i.e., thinness) in right fusiform gyrus (rFG) compared to NU (p<0.05). Thalamic volume was significantly smaller in MJ users compared to NU (right, p=0.05; left, p=0.01) and associated with greater non-planning (p<0.01) and overall impulsivity (p=0.04). There were no other group differences. ConclusionsRFG cortical thinness and smaller thalamic volume in emerging adults is associated with MJ abuse. Furthermore, smaller thalamic volume associated with greater impulsivity contributes to growing evidence that the thalamus is neurobiologically perturbed by MJ use. Collectively, altered thalamic and rFG structural integrity may interfere with their known roles in regulating visuoperceptual and object information processing.

Relationship between Personality and Gray Matter Volume in Healthy Young Adults: A Voxel-Based Morphometric Study

This study aims to investigate the neurostructural foundations of the human personality in young adults. High-resolution structural T1-weighted MR images of 71 healthy young individuals were processed using voxel-based morphometric (VBM) approach. Multiple regression analyses were performed to identify the associations between personality traits and gray matter volume (GMV). The Eysenck Personality Questionnaire-Revised, Short Scale for Chinese was chosen to assess the personality traits. This scale includes four dimensions, namely, extraversion, neuroticism, psychoticism, and lie. Particularly, we studied on two dimensions (extraversion and neuroticism) of Eysenck’s personality. Our results showed that extraversion was negatively correlated with GMV of the bilateral amygdala, the bilateral parahippocampal gyrus, the right middle temporal gyrus, and the left superior frontal gyrus, all of which are involved in emotional and social cognitive processes. These results might suggest an association between extraversion and affective processing. In addition, a positive correlation was detected between neuroticism and GMV of the right cerebellum, a key brain region for negative affect coordination. Meanwhile, a negative association was revealed between GMV of the left superior frontal gyrus and neuroticism. These results may prove that neuroticism is related to several brain regions involved in regulating negative emotions. Based on those findings, we concluded that brain regions involved in social cognition and affective process accounted for modulation and shaping of personality traits among young individuals. Results of this study may serve as a basis for elucidating the anatomical factors of personality.

Sex differences in resilience to childhood maltreatment: Effects of trauma history on hippocampal volume, general cognition and subclinical psychosis in healthy adults

Recent data suggests that a history of childhood maltreatment is associated with reductions in hippocampal volume in healthy adults. Because this association is also evident in adults with psychiatric illness, it has been suggested that reductions in hippocampal volume associated with childhood maltreatment may be a risk factor for psychiatric illness. Such an interpretation suggests that healthy adults with a history of childhood maltreatment are more resilient to the effects of maltreatment. Current models of resilience suggest, however, that resiliency should be measured across multiple domains of functioning. The present study sought to investigate childhood maltreatment in relationship to hippocampal volumes in healthy adults and to address the question of whether the putative resiliency extends to other domains of functioning. Sixty-seven healthy Caucasian adults were assessed for a history of childhood emotional abuse, emotional neglect and physical abuse and received high resolution structural MR imaging scans. Participants with and without histories of abuse or neglect were compared on measures of total hippocampal volume, general cognitive ability and subclinical psychopathology. Our results suggest that childhood emotional abuse is associated with reduced hippocampus volume in males, but not in females. However, emotional abuse was associated with higher levels of subclinical psychopathology in both males and females. These data suggest that while females may be more resilient to the neurological effects of childhood maltreatment, they are not more resilient to the psychiatric symptoms associated with childhood maltreatment. Further research is needed to elucidate the mechanisms involved in these different levels of resilience.

MRI of carriers of the apolipoprotein E e4 allele–evidence for structural differences in normal‐appearing brain tissue in e4+ relative to e4– young adults

Apolipoprotein E is a protein involved in cholesterol and lipid transport. The gene coding for this protein has three different alleles: e2, e3 and e4. The e4 allele is recognised as a significant risk factor for the development of Alzheimer's disease in later life. Paradoxically, behavioural and functional evidence has demonstrated that the e4 allele may confer a cognitive advantage to the carrier in youth. In this article, a range of sophisticated and novel structural imaging techniques were used to identify subtle differences in the brain tissue of groups of young e4 and homozygous e3 carriers that might support this paradox. Using voxel-based morphometry of high-resolution structural MR images, we identified a higher white matter volume ratio in e4 relative to homozygous e3 carriers. Furthermore, diffusion tensor imaging and tract-based spatial statistics studies identified increases in axial diffusivity and mode of anisotropy in carriers of the e4 allele. In addition, quantitative magnetisation transfer data were analysed using tract-based spatial statistics. Evidence of a trend towards an increased transverse relaxation time of the bound proton pool was detected in e4 carriers, indicative of altered white matter composition. These changes were found to correlate with indices of cognitive performance across the two groups, supporting the notion that such subtle differences in white matter integrity may confer neural advantages that contribute to cognitive outcomes and, potentially, to performance differences, such as observed here in a test of verbal fluency and reported previously by other researchers. Copyright © 2013 John Wiley & Sons, Ltd.

Extraversion Is Linked to Volume of the Orbitofrontal Cortex and Amygdala

Neuroticism and extraversion are personality factors associated with the vulnerability for developing depression and anxiety disorders, and are possibly differentially related to brain structures implicated in the processing of emotional information and the generation of mood states. To date, studies on brain morphology mainly focused on neuroticism, a dimension primarily related to negative affect, yielding conflicting findings concerning the association with personality, partially due to methodological issues and variable population samples under study. Recently, extraversion, a dimension primarily related to positive affect, has been repeatedly inversely related to with symptoms of depression and anxiety disorders. In the present study, high resolution structural T1-weighted MR images of 65 healthy adults were processed using an optimized Voxel Based Morphometry (VBM) approach. Multiple regression analyses were performed to test for associations of neuroticism and extraversion with prefrontal and subcortical volumes. Orbitofrontal and right amygdala volume were both positively related to extraversion. Extraversion was differentially related to volume of the anterior cingulate cortex in males (positive) and females (negative). Neuroticism scores did not significantly correlate with these brain regions. As extraversion is regarded a protective factor for developing anxiety disorders and depression and has been related to the generation of positive affect, the present results indicate that the reduced likelihood of developing affective disorders in individuals high on extraversion is related to modulation of emotion processing through the orbitofrontal cortex and the amygdala.

A Library of Cortical Morphology Analysis Tools to Study Development, Aging and Genetics of Cerebral Cortex

Sharing of analysis techniques and tools is among the main driving forces of modern neuroscience. We describe a library of tools developed to quantify global and regional differences in cortical anatomy in high resolution structural MR images. This library is distributed as a plug-in application for popular structural analysis software, BrainVisa (BV). It contains tools to measure global and regional gyrification, gray matter thickness and sulcal and gyral white matter spans. We provide a description of each tool and examples for several case studies to demonstrate their use. These examples show how the BV library was used to study cortical folding process during antenatal development and recapitulation of this process during cerebral aging. Further, the BV library was used to perform translation research in humans and non-human primates on the genetics of cerebral gyrification. This library, including source code and self-contained binaries for popular computer platforms, is available from the NIH-Neuroimaging Informatics Tools and Resources Clearinghouse (NITRC) resource ( http://www.nitrc.org/projects/brainvisa_ext ).

Differences in Cortical Thickness in Healthy Controls, Subjects with Mild Cognitive Impairment, and Alzheimer's Disease Patients: A Longitudinal Study

In this study, we analyzed differences in cortical thickness (CTH) between healthy controls (HC), subjects with stable mild cognitive impairment (S-MCI), progressive MCI (P-MCI), and Alzheimer's disease (AD), and assessed correlations between CHT and clinical disease severity, education, and apolipoprotein E4 (APOE) genotype. Automated CTH analysis was applied to baseline high-resolution structural MR images of 145 subjects with a maximum followup time of 7.4 years pooled from population-based study databases held in the University of Kuopio. Statistical differences in CTH between study groups and significant correlations between CTH and clinical and demographic factors were assessed and displayed on a cortical surface model. Compared to HC group (n = 26), the AD (n = 21) group displayed significantly reduced CTH in several areas of frontal and temporal cortices of the right hemisphere. Higher education and lower MMSE scores were correlated with reduced CTH in the AD group, whereas no significant correlation was found between CDR-SB scores or APOE genotype and CTH. The P-MCI group demonstrated significantly reduced CTH compared to S-MCI in frontal, temporal and parietal cortices even after statistically adjusting for all confounding variables. Ultimately, analysis of CTH can be used to detect cortical thinning in subjects with progressive MCI several years before conversion and clinical diagnosis of AD dementia, irrespective of their cognitive performance, education level, or APOE genotype.

Altered Neurocircuitry in the Dopamine Transporter Knockout Mouse Brain

The plasma membrane transporters for the monoamine neurotransmitters dopamine, serotonin, and norepinephrine modulate the dynamics of these monoamine neurotransmitters. Thus, activity of these transporters has significant consequences for monoamine activity throughout the brain and for a number of neurological and psychiatric disorders. Gene knockout (KO) mice that reduce or eliminate expression of each of these monoamine transporters have provided a wealth of new information about the function of these proteins at molecular, physiological and behavioral levels. In the present work we use the unique properties of magnetic resonance imaging (MRI) to probe the effects of altered dopaminergic dynamics on meso-scale neuronal circuitry and overall brain morphology, since changes at these levels of organization might help to account for some of the extensive pharmacological and behavioral differences observed in dopamine transporter (DAT) KO mice. Despite the smaller size of these animals, voxel-wise statistical comparison of high resolution structural MR images indicated little morphological change as a consequence of DAT KO. Likewise, proton magnetic resonance spectra recorded in the striatum indicated no significant changes in detectable metabolite concentrations between DAT KO and wild-type (WT) mice. In contrast, alterations in the circuitry from the prefrontal cortex to the mesocortical limbic system, an important brain component intimately tied to function of mesolimbic/mesocortical dopamine reward pathways, were revealed by manganese-enhanced MRI (MEMRI). Analysis of co-registered MEMRI images taken over the 26 hours after introduction of Mn2+ into the prefrontal cortex indicated that DAT KO mice have a truncated Mn2+ distribution within this circuitry with little accumulation beyond the thalamus or contralateral to the injection site. By contrast, WT littermates exhibit Mn2+ transport into more posterior midbrain nuclei and contralateral mesolimbic structures at 26 hr post-injection. Thus, DAT KO mice appear, at this level of anatomic resolution, to have preserved cortico-striatal-thalamic connectivity but diminished robustness of reward-modulating circuitry distal to the thalamus. This is in contradistinction to the state of this circuitry in serotonin transporter KO mice where we observed more robust connectivity in more posterior brain regions using methods identical to those employed here.

A comparison of automated segmentation and manual tracing for quantifying hippocampal and amygdala volumes

Large databases of high-resolution structural MR images are being assembled to quantitatively examine the relationships between brain anatomy, disease progression, treatment regimens, and genetic influences upon brain structure. Quantifying brain structures in such large databases cannot be practically accomplished by expert neuroanatomists using hand-tracing. Rather, this research will depend upon automated methods that reliably and accurately segment and quantify dozens of brain regions. At present, there is little guidance available to help clinical research groups in choosing such tools. Thus, our goal was to compare the performance of two popular and fully automated tools, FSL/FIRST and FreeSurfer, to expert hand tracing in the measurement of the hippocampus and amygdala. Volumes derived from each automated measurement were compared to hand tracing for percent volume overlap, percent volume difference, across-sample correlation, and 3-D group-level shape analysis. In addition, sample size estimates for conducting between-group studies were computed for a range of effect sizes. Compared to hand tracing, hippocampal measurements with FreeSurfer exhibited greater volume overlap, smaller volume difference, and higher correlation than FIRST, and sample size estimates with FreeSurfer were closer to hand tracing. Amygdala measurement with FreeSurfer was also more highly correlated to hand tracing than FIRST, but exhibited a greater volume difference than FIRST. Both techniques had comparable volume overlap and similar sample size estimates. Compared to hand tracing, a 3-D shape analysis of the hippocampus showed FreeSurfer was more accurate than FIRST, particularly in the head and tail. However, FIRST more accurately represented the amygdala shape than FreeSurfer, which inflated its anterior and posterior surfaces.

Multimodality Data Integration in Epilepsy

An important goal of software development in the medical field is the design of methods which are able to integrate information obtained from various imaging and nonimaging modalities into a cohesive framework in order to understand the results of qualitatively different measurements in a larger context. Moreover, it is essential to assess the various features of the data quantitatively so that relationships in anatomical and functional domains between complementing modalities can be expressed mathematically. This paper presents a clinically feasible software environment for the quantitative assessment of the relationship among biochemical functions as assessed by PET imaging and electrophysiological parameters derived from intracranial EEG. Based on the developed software tools, quantitative results obtained from individual modalities can be merged into a data structure allowing a consistent framework for advanced data mining techniques and 3D visualization. Moreover, an effort was made to derive quantitative variables (such as the spatial proximity index, SPI) characterizing the relationship between complementing modalities on a more generic level as a prerequisite for efficient data mining strategies. We describe the implementation of this software environment in twelve children (mean age 5.2 ± 4.3 years) with medically intractable partial epilepsy who underwent both high-resolution structural MR and functional PET imaging. Our experiments demonstrate that our approach will lead to a better understanding of the mechanisms of epileptogenesis and might ultimately have an impact on treatment. Moreover, our software environment holds promise to be useful in many other neurological disorders, where integration of multimodality data is crucial for a better understanding of the underlying disease mechanisms.

EEG/(f)MRI measurements at 7 Tesla using a new EEG cap (“InkCap”)

We aimed at improving the signal-to-noise ratio (SNR) of electroencephalography (EEG) during magnetic resonance imaging (MRI) by introducing a new EEG cap (“InkCap”) based on conductive ink technology. The InkCap was tested with temperature measurements on an electrically conductive phantom head and during structural and functional MRI (fMRI) recordings in 11 healthy human volunteers at 7 T. Combined EEG/fMRI measurements were conducted to study the interaction between the two modalities. The EEG recordings with the InkCap demonstrated up to a five-fold average decrease in signal variance during echo-planar imaging, with respect to a cap made of standard carbon fiber leads. During concurrent EEG/fMRI measurements in human volunteers, alpha oscillations were clearly detected at 7 T. Minimal artifacts were present in the T2* and high-resolution structural MR images of the brain parenchyma. Our results show that the InkCap technology considerably improves the quality of both EEG and (f)MRI during concurrent measurements even at 7 T.

Event‐related fMRI of Myoclonic Jerks Arising from Dysplastic Cortex

Malformations of cortical development can cause epileptiform activity and myoclonic jerks, yet EEG correlates of jerks can be difficult to obtain. We studied a woman who had frequent episodes of persistent right-foot jerking since childhood. Ictal and interictal EEG had shown no localizing epileptiform activity. Functional imaging experiments were performed with concurrent video monitoring to document the timing of foot jerks. These studies mapped brain regions controlling voluntary right- and left-foot movements, and spontaneous right-foot jerks. High-resolution structural MR imaging revealed a dysplastic gyrus extending anteriorly off the left central sulcus. Event-related analysis of spontaneous jerks revealed prominent activation of the left precentral gyrus (right-foot motor area), bilateral medial frontal regions (supplementary motor area), and the dysplastic gyrus. Hemodynamic response modeling to foot jerks revealed the hemodynamic response peaked earlier in the dysplastic cortex and SMA regions than in the foot area. Event-related fMRI in a patient with spontaneous and induced epileptic foot jerks revealed brain regions active during jerks. The results of this analysis allowed us to tailor subsequent intracerebral recordings. Analysis of the timing of the hemodynamic response showed certain brain regions with an earlier rise in BOLD signal, suggesting a possible initiating role, or different hemodynamic response functions. Hemodynamic response timing should be considered carefully when interpreting event-related studies of epileptiform activity.

Observer‐independent analysis of high‐resolution MR images of the human cerebral cortex: In vivo delineation of cortical areas

Using high-resolution MRI, it is now possible to examine the living human cortex down to a resolution of less than 300 mum. Thus, in vivo imaging is now approaching the resolution that has been successfully used in histological analysis of the cerebral cortex for many years, e.g., low-magnification light microscopy. This allows unprecedented views of cortical microstructure that reflect defined histological features, specifically, individual cortical layers. As in histological brain mapping, it is possible to use the changes in the cortical lamination patterns to define individual cortical areas. This allows in vivo neuroanatomical maps to be generated for individual subjects and precise correlation of the results from functional imaging studies in these subjects with their own microanatomical information. To this end, we adapted the well-established observer-independent cytoarchitectonic mapping techniques for defining cortical borders based on changes in cortical lamination for in vivo parcellation of high-resolution structural MR images.