Katrin Amunts

Neurology, Histology, Neurolinguistics

46.12

Publications

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    ABSTRACT: Objective: The heterogeneous human frontal pole has been identified as a node in the dysfunctional network of major depressive disorder. The contribution of the medial (socio-affective) versus lateral (cognitive) frontal pole to major depression pathogenesis is currently unclear. The authors performed morphometric comparison of the microstructurally informed subdivisions of human frontal pole between depressed patients and comparison subjects using both uni- and multivariate statistics. Method: Multisite voxel- and region-based morphometric MRI analysis was conducted in 73 depressed patients and 73 matched comparison subjects without psychiatric history. Frontal pole volume was first compared between depressed patients and comparison subjects by subdivision-wise classical morphometric analysis. In a second approach, frontal pole volume was compared by subdivision-naive multivariate searchlight analysis based on support vector machines. Results: Subdivision-wise morphometric analysis found a significantly smaller medial frontal pole in depressed patients, with a negative correlation of disease severity and duration. Histologically uninformed multivariate voxel-wise statistics provided converging evidence for structural aberrations specific to the microstructurally defined medial area of the frontal pole in depressed patients. Conclusions: Across disparate methods, subregion specificity in the left medial frontal pole volume in depressed patients was demonstrated. Indeed, the frontal pole was shown to structurally and functionally connect to other key regions in major depression pathology, such as the anterior cingulate cortex and the amygdala via the uncinate fasciculus. Present and previous findings consolidate the left medial portion of the frontal pole as particularly altered in major depression.
    Full-text · Article · Jan 2016 · American Journal of Psychiatry
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    ABSTRACT: Historically, the human frontal pole (FP) has been considered as a single architectonic area. Brodmann's area 10, in the frontal lobe with known contributions in the execution of various higher order cognitive processes. However, recent cytoarchitectural studies of the FP in humans have shown that this portion of cortex contains two distinct cytoarchitectonic regions. Since architectonic differences are accompanied by differential connectivity and functions, the frontal pole qualifies as a candidate region for exploratory parcellation into functionally discrete sub-regions. We investigated whether this functional heterogeneity is reflected in distinct segregations within cytoarchitectonically defined FP-areas using meta-analytic co-activation based parcellation (CBP). The CBP method examined the co-activation patterns of all voxels within the FP as reported in functional neuroimaging studies archived in the BrainMap database. Voxels within the FP were subsequently clustered into sub-regions based on the similarity of their respective meta-analytically derived co-activation maps. Performing this CBP analysis on the FP via k-means clustering produced a distinct 3-cluster parcellation for each hemisphere corresponding to previously identified cytoarchitectural differences. Post-hoc functional characterization of clusters via BrainMap metadata revealed that lateral regions of the FP mapped to memory and emotion domains, while the dorso- and ventromedial clusters were associated broadly with emotion and social cognition processes. Furthermore, the dorsomedial regions contain an emphasis on theory of mind and affective related paradigms whereas ventromedial regions couple with reward tasks. Results from this study support previous segregations of the FP and provide meta-analytic contributions to the ongoing discussion of elucidating functional architecture within human FP. Copyright © 2015. Published by Elsevier Inc.
    Full-text · Article · Jan 2016 · NeuroImage
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    ABSTRACT: The basal forebrain comprises heterogeneous structures located close to the medial and ventral surfaces of the cerebral hemispheres. This region contains a number of interdigitating anatomical structures, including the basal nucleus of Meynert, the ventral striatum (nucleus accumbens), and the cell groups underneath the globus pallidus in the substantia innominata that bridge the centromedial amygdala to the bed nucleus of the stria terminalis (‘extended amygdala’). This region is involved in cortical activation, attention, learning, memory, reward, cortical plasticity, and also disease states: cholinergic corticopetal projection neurons degenerate in Alzheimer's and related disorders. Recent studies using postmortem probabilistic maps and resting-state functional connectivity analysis have begun to shed light on distinct and shared functions across the complex anatomical landscape of the ventral forebrain.
    No preview · Article · Dec 2015
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    ABSTRACT: Transmitter receptors are key molecules of signal processing in the brain. They occur at different densities between different cortical regions and layers, as well as subcortical nuclei. The differences enable mapping of these structures based on the density of a single or multiple receptors in each structure. We summarize data of selected receptor types of classical transmitter systems in the human cerebral cortex, cerebellum, hippocampus, amygdala, basal ganglia, and thalamus. A short review of developmental and age-related changes is also provided. Finally, we show the relevance of multireceptor analyses (receptor fingerprints) for the characterization of functional systems at the molecular level.
    No preview · Article · Dec 2015
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    ABSTRACT: This article focuses on the cytoarchitectonic organization of the cerebral cortex and its segregation into cortical areas. Cytoarchitecture describes the spatial distribution of neuronal cell types, their arrangement in horizontal layers and vertical columns, as well as cortical thickness. Based on cytoarchitectonic characteristics, the cortex is divided into iso- and allocortex, with the mesocortex as a transition region between both. Some emphasis is put on the presentation of nearly forgotten but still relevant classical cytoarchitectonic maps which are discussed in the light of recent quantitative microscopical analyses and studies of intersubject variability (probability maps) as well as functional imaging data.
    No preview · Article · Dec 2015
  • K. Amunts · M. Catani
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    ABSTRACT: Anatomical models of language include a core left perisylvian network between Wernicke's region in the temporal lobe and Broca's region in the frontal lobe. In addition, a number of other cortical areas and subcortical nuclei contribute to language functions. This extended language network comprises the inferior parietal cortex (i.e., Geschwind's region), the anterior temporal lobe, the anterior insula, the presupplementary motor area, and the lateral occipitotemporal cortex (i.e., visual word form area). At the subcortical level, the thalamus, basal ganglia, and cerebellum are reciprocally connected to cortical language regions and modulate their activity. In this article, we describe the anatomy of the language cortical regions as defined by their neuronal composition and layering (i.e., cytoarchitectonics) and the receptor distribution for the main neurotransmitters of the central nervous system (i.e., receptorarchitectonics). The principal association, projection, and commissural language pathways described by recent diffusion tractography studies will also be reviewed. A particular focus of this article is to characterize the anatomical interindividual variability and its relevance to function in the normal brain and in language disorders.
    No preview · Article · Dec 2015
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    ABSTRACT: Introduction: Whole-body magnetic resonance (MR) imaging is increasingly implemented in population-based cohorts and clinical settings. However, to quantify the variability introduced by the different scanners is essential to make conclusions about clinical and biological data, and relevant for internal/external validity. Thus, we determined the interscanner and intrascanner variability of different 3 T MR scanners for whole-body imaging. Methods: Thirty volunteers were enrolled to undergo multicentric, interscanner as well intrascanner imaging as part of the German National Cohort pilot studies. A comprehensive whole-body MR protocol was installed at 9 sites including 7 different MR scanner models by all 4 major vendors. A set of quantitative, organ-specific measures (n = 20; eg, volume of brain's gray/white matter, pulmonary trunk diameter, vertebral body height) were obtained in blinded fashion. Reproducibility was determined using mean weighted relative differences and intraclass correlation coefficients. Results: All participants (44 ± 14 years, 50% female) successfully completed the imaging protocol except for two because of technical issues. Mean scan time was 2 hours and 32 minutes and differed significantly across scanners (range, 1 hour 59 minutes to 3 hours 12 minutes). A higher reproducibility of obtained measurements was observed for intrascanner than for interscanner comparisons (intraclass correlation coefficients, 0.80 ± 0.17 vs 0.60 ± 0.31, P = 0.005, respectively). In the interscanner comparison, mean relative difference ranged from 1.0% to 53.2%. Conversely, in the intrascanner comparison, mean relative difference ranged from 0.1% to 15.6%. There were no statistical differences for intrascanner and interscanner reproducibility between the different organ foci (all P ≥ 0.24). Conclusions: While whole-body MR imaging-derived, organ-specific parameters are generally associated with good to excellent reproducibility, smaller differences are obtained when using identical MR scanner models by a single vendor.
    No preview · Article · Dec 2015 · Investigative radiology
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    ABSTRACT: Previous architectonical studies of human orbitofrontal cortex (OFC) provided divergent maps regarding number, location, and extent of areas. To solve this controversy, an observer-independent cytoarchitectonical mapping of medial OFC (mOFC) was performed. Borders of cortical areas were detected in histological sections of ten human post-mortem brains using a quantitative, statistically testable method, and their stereotaxic localization and intersubject variability were determined. Three areas were identified: granular Fo1 mainly on the rostral Gyrus rectus and medial of the olfactory sulcus; granular to dysgranular Fo2, mainly on the posterior part of the ventromedial Gyrus rectus and the medial and lateral banks of the olfactory sulcus; granular Fo3 between the olfactory and medial or intermediate orbital sulci. Fo3 was bordered medially by Fo1 and Fo2 and laterally by the lateral OFC (lOFC). A cluster analysis of the cytoarchitectonical features of Fo1-Fo3, subgenual cingulate areas, BA12, lateral and medial areas of the frontopolar cortex, lOFC and areas of Broca's region demonstrated the cytoarchitectonical similarity between the mOFC areas in contrast to all other frontal areas. Probabilistic maps of mOFC areas show a considerable intersubject variability in extent and position in stereotaxic space, and provide spatial templates for anatomical localization of in vivo neuroimaging data via the JuBrain atlas and the Anatomy Toolbox.
    Full-text · Article · Dec 2015 · Cortex
  • Katrin Amunts · Karl Zilles

    No preview · Article · Dec 2015 · Neuron
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    ABSTRACT: Parkinson's disease (PD) is a well-characterized neurological disorder with regard to its neuropathological and symptomatic appearance. At the genetic level, mutations of particular genes, e.g. Parkin and DJ-1, were found in human hereditary PD with early onset. Neurotransmitter receptors constitute decisive elements in neural signal transduction. Furthermore, since they are often altered in neurological and psychiatric diseases, receptors have been successful targets for pharmacological agents. However, the consequences of PD-associated gene mutations on the expression of transmitter receptors are largely unknown. Therefore, we studied the expression of 16 different receptor binding sites of the neurotransmitters glutamate, GABA, acetylcholine, adrenaline, serotonin, dopamine and adenosine by means of quantitative receptor autoradiography in Parkin and DJ-1 knockout mice. These knockout mice exhibit electrophysiological and behavioral deficits, but do not show the typical dopaminergic cell loss. We demonstrated differential changes of binding site densities in eleven brain regions. Most prominently, we found an up-regulation of GABAB and kainate receptor densities in numerous cortical areas of Parkin and DJ-1 knockout mice, as well as increased NMDA but decreased AMPA receptor densities in different brain regions of the Parkin knockout mice. The alterations of three different glutamate receptor types may indicate the potential relevance of the glutamatergic system in the pathogenesis of PD. Furthermore, the cholinergic M1, M2 and nicotinic receptors as well as the adrenergic α2 and the adenosine A2A receptors showed differentially increased densities in Parkin and DJ-1 knockout mice. Taken together, knockout of the PD-associated genes Parkin or DJ-1 results in differential changes of neurotransmitter receptor densities, highlighting a possible role of altered non-dopaminergic, and in particular of glutamatergic neurotransmission in PD pathogenesis.
    Full-text · Article · Nov 2015 · Neuroscience
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    ABSTRACT: The assessment of motor and executive functions following stroke or traumatic brain injury is a key aspect of impairment evaluation and used to guide further therapy. In clinical routine, such assessments are largely dominated by pen-and-paper tests. While these provide standardized, reliable, and ecologically valid measures of the individual level of functioning, rather little is yet known about their neurobiological underpinnings. Therefore, the aim of this study was to investigate brain regions and their associated networks that are related to upper extremity motor function, as quantified by the motor speed subtest of the trail making test (TMT-MS). Whole-brain voxel-based morphometry and whole-brain tract-based spatial statistics were used to investigate the association between TMT-MS performance with gray-matter volume (GMV) and white-matter integrity, respectively. While results demonstrated no relationship to local white-matter properties, we found a significant correlation between TMT-MS performance and GMV of the lower bank of the inferior frontal sulcus, a region associated with cognitive processing, as indicated by assessing its functional profile by the BrainMap database. Using this finding as a seed region, we further examined and compared networks as reflected by resting state connectivity, meta-analytic connectivity modeling, structural covariance, and probabilistic tractography. While differences between the different approaches were observed, all approaches converged on a network comprising regions that overlap with the multiple-demand network. Our data therefore indicate that performance may primarily depend on executive function, thus suggesting that motor speed in a more naturalistic setting should be more associated with executive rather than primary motor function. Moreover, results showed that while there were differences between the approaches, a convergence indicated that common networks can be revealed across highly divergent methods.
    Full-text · Article · Oct 2015 · Frontiers in Neurology
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    ABSTRACT: Areas of the fusiform gyrus (FG) within human ventral temporal cortex (VTC) process high-level visual information associated with faces, limbs, words, and places. Since classical cytoarchitectonic maps do not adequately reflect the functional and structural heterogeneity of the VTC, we studied the cytoarchitectonic segregation in a region, which is rostral to the recently identified cytoarchitectonic areas FG1 and FG2. Using an observer-independent and statistically testable parcellation method, we identify 2 new areas, FG3 and FG4, in 10 human postmortem brains on the mid-FG. The mid-fusiform sulcus reliably identifies the cytoarchitectonic transition between FG3 and FG4. We registered these cytoarchitectonic areas to the common reference space of the single-subject Montreal Neurological Institute (MNI) template and generated probability maps, which reflect the intersubject variability of both areas. Future studies can relate in vivo neuroimaging data with these microscopically defined cortical areas to functional parcellations. We discuss these results in the context of both large-scale functional maps and fine-scale functional clusters that have been identified within the human VTC. We propose that our observer-independent cytoarchitectonic parcellation of the FG better explains the functional heterogeneity of the FG compared with the homogeneity of classic cytoarchitectonic maps.
    Full-text · Article · Oct 2015 · Cerebral Cortex
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    ABSTRACT: The neuroimaging technique three-dimensional polarized light imaging (3D-PLI) provides a high-resolution reconstruction of nerve fibres in human post-mortem brains. The orientations of the fibres are derived from birefringence measurements of histological brain sections assuming that the nerve fibres - consisting of an axon and a surrounding myelin sheath - are uniaxial birefringent and that the measured optic axis is oriented in direction of the nerve fibres (macroscopic model). Although experimental studies support this assumption, the molecular structure of the myelin sheath suggests that the birefringence of a nerve fibre can be described more precisely by multiple optic axes oriented radially around the fibre axis (microscopic model). In this paper, we compare the use of the macroscopic and the microscopic model for simulating 3D-PLI by means of the Jones matrix formalism. The simulations show that the macroscopic model ensures a reliable estimation of the fibre orientations as long as the polarimeter does not resolve structures smaller than the diameter of single fibres. In the case of fibre bundles, polarimeters with even higher resolutions can be used without losing reliability. When taking the myelin density into account, the derived fibre orientations are considerably improved.
    No preview · Article · Oct 2015 · Journal of The Royal Society Interface
  • J. Caspers · S B Eickhoff · K. Amunts · G. Antoch · K. Zilles
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    ABSTRACT: Purpose: To investigate the distribution of co-activation patterns of the recently identified ventral visual areas FG1 and FG2 of the posterior fusiform gyrus using the novel meta-analytic approach PaMiNI (Pattern Mining in NeuroImaging). Materials and Methods: All neuroimaging experiments reporting activation foci within FG1 or FG2 were retrieved from the BrainMap database. The stereotaxic activation foci in standard reference space were analyzed with PaMiNI. Here, Gaussian mixture modeling was applied to the stereotaxic coordinates of all foci to identify the underlying brain regions of each dataset. Then, association analysis was performed to reveal frequent co-activations across the modeled brain regions. Results: Co-activation patterns of FG1 were mainly found within the visual system, i.e. in early visual areas, and were symmetrically distributed across both hemispheres. FG2 features several extra-visual co-activations, mainly to inferior frontal, premotor and parietal regions. Furthermore, the co-activations of FG2 showed clear lateralization to the left FG2. Conclusion: FG1 shows characteristics of an intermediate visual area between the early ventral visual cortex and the category-specific higher-order areas. Co-activation patterns of FG2 indicate that FG2 is a higher-order visual area that probably corresponds to the posterior fusiform face area and partly the visual word-form area.
    No preview · Article · Sep 2015 · RöFo - Fortschritte auf dem Gebiet der R
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    Full-text · Dataset · Sep 2015
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    ABSTRACT: Structural connectivity of the brain can be conceptionalized as a multiscale organization. The present study is built on 3D-Polarized Light Imaging (3D-PLI), a neuroimaging technique targeting the reconstruction of nerve fiber orientations and therefore contributing to the analysis of brain connectivity. Spatial orientations of the fibers are derived from birefringence measurements of unstained histological sections that are interpreted by means of a voxel-based analysis. This implies that a single fiber orientation vector is obtained for each voxel, which reflects the net effect of all comprised fibers. We have utilized two polarimetric setups providing an object space resolution of 1.3\,{\textmu}m/px (microscopic setup) and 64\,{\textmu}m/px (macroscopic setup) to carry out 3D-PLI and retrieve fiber orientations of the same tissue samples, but at complementary voxel sizes (i.e., scales). The present study identifies the main sources which cause a discrepancy of the measured fiber orientations observed when measuring the same sample with the two polarimetric systems. As such sources the differing optical resolutions and diverging retardances of the implemented waveplates were identified. A methodology was implemented that enables the compensation of measured different systems' responses to the same birefringent sample. This opens up new ways to conduct multiscale analysis in brains by means of 3D-PLI and to provide a reliable basis for the transition between different scales of the nerve fiber architecture.
    Full-text · Article · Sep 2015 · Frontiers in Neuroanatomy
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    Full-text · Dataset · Aug 2015
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    Full-text · Dataset · Aug 2015
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    ABSTRACT: Meta-analytic techniques allow cognitive neuroscientists to pool large amounts of data across many individual task-based functional neuroimaging experiments. These methods have been aided by the introduction of online databases such as Brainmap.org or Neurosynth.org, which collate peak activation coordinates obtained from thousands of published studies. Findings from meta-analytic studies typically include brain regions which are consistently activated across studies for specific contrasts, investigating cognitive or clinical hypotheses. These regions can be subsequently used as the basis for seed-based connectivity analysis, or formally compared to neuroimaging data in order to help interpret new findings. To facilitate such approaches, we have developed a new online repository of meta-analytic neuroimaging results, named the Archive of Neuroimaging Meta-analyses (ANIMA). The ANIMA platform consists of an intuitive online interface for querying, downloading, and contributing data from published meta-analytic studies. Additionally, to aid the process of organizing, visualizing, and working with these data, we present an open-source desktop application called Volume Viewer. Volume Viewer allows users to easily arrange imaging data into composite stacks, and save these sessions as individual files, which can also be uploaded to the ANIMA database. The application also allows users to perform basic functions, such as computing conjunctions between images, or extracting regions-of-interest or peak coordinates for further analysis. The introduction of this new resource will enhance the ability of researchers to both share their findings and incorporate existing meta-analytic results into their own research. Copyright © 2015. Published by Elsevier Inc.
    Full-text · Article · Jul 2015 · NeuroImage

  • No preview · Article · Jun 2015 · Sprache · Stimme · Gehör

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