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Miscellaneous Critical avalanches in a spatially structured model of cortical On-Off dynamics Zeraati, R., Engel, T., Levina, A. Bernstein Conference 2018, 2018
{Cortical activity is permeated with endogenously generated fluctuations that affect responses to sensory stimuli and correlate with behavioral variability. These ongoing dynamics have been studied on two different spatial scales. On a local scale of single cortical columns, ongoing activity spontaneously transitions between episodes of vigorous (On) and faint (Off) spiking, synchronously across cortical layers. Dynamics of these local On-Off transitions are modulated during goal-directed behavior and predict behavioral performance [1]. On a wider spatial scale of interacting cortical columns, spontaneous activity propagates as cascades of bursts known as neural avalanches. The size of these avalanches is well approximated by a power-law distribution, suggesting that brain operates close to a critical point [2], which was shown to be optimal for information processing [3,4]. Whether and how local On-Off dynamics can coexist with critical avalanches in the same network is still an open question. To investigate this question, we developed a branching model capable of capturing both the local On-Off dynamics and the propagation of neural avalanches on a wider spatial scale. Each unit in the model represents a cortical column, with a spatially structured connectivity to other units mimicking the cortex spatial organization. The columns spontaneously transition between On and Off episodes driven by a self-excitation, excitatory inputs from the neighboring columns, and by stochastic external inputs. On and Off episode durations in our model follow exponential distributions, similar to the On-Off dynamics observed in single cortical columns (Fig 1C) [1]. We examined under what conditions these local On-Off dynamics are consistent with the propagation of critical avalanches. We found that models with local connectivity do not exhibit critical dynamics in the limit of a large system size. In a critical model, the cut-off of the avalanche-size distribution is expected to scale with the system size. In contrast, in models with only nearest-neighbor connectivity, the cut-off stays constant for systems larger than some characteristic size-scale. We demonstrate that the scaling property can be recovered with a larger radius of connections or by rewiring a small fraction of local connections to long-range random connections (Fig 1D-E). Our results highlight the possible role of long-range connections in the cortex in defining the operating regime of the brain dynamics.}
DOI BibTeX
Article Crystal structure of 8-(4-methyl­phen­yl)-2′-de­oxy­adenosine hemihydrate Ardhapure, A., Sanghvi, Y., Borozdina, Y., Kapdi, A., Schulzke, C. {Acta Crystallographica Section E: Crystallographic Communications}, 74(1):1-5, 2018
{In the asymmetric unit, equalling the unit cell (triclinic, P1, Z \textequals 1), two mol­ecules of the title compound, 8-(4-methyl­phen­yl)-D-2′-de­oxy­adenosine, C17H19N5O3, are present, with distinct conformations of the two sugar moieties, together with one solvent water mol­ecule. All three ribose O atoms are involved in hydrogen bonding and the crystal packing is largely determined by hydrogen-bonding or hydrogen\textendashheteroatom inter­actions (O\textemdashH...O, O\textemdashH...N, N\textemdashH...O, C\textemdashH...O and C\textemdashH...N) with one independent mol­ecule directly linked to four neighbouring mol­ecules and the other mol­ecule directly linked to six neighbouring mol­ecules. The two independent mol­ecules of the asymmetric unit display three weak intra­molecular C\textemdashH-to-heteroatom contacts, two of which are very similar despite the different conformations of the deoxyribosyl moieties. The aromatic ring systems of both mol­ecules are in proximity to each other and somehow aligned, though not coplanar. The absolute structures of the two mol­ecules were assumed with reference to the reactant 8-bromo-D-2′-de­oxy­adenosine as they could not be determined crystallographically.}
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Modern Magnetic Systems Article Current-induced skyrmion generation through morphological thermal transitions in chiral ferromagnetic heterostructures Lemesh, I., Litzius, K., Böttcher, M., Bassirian, P., Kerber, N., Heinze, D., Zázvorka, J., Büttner, F., Caretta, L., Mann, M., Weigand, M., Finizio, S., Raabe, J., Im, M., Stoll, H., Schütz, G., Dupé, B., Kläui, M., Beach, G. S. D. {Advanced Materials}, 30(49), Wiley-VCH, Weinheim, 2018 DOI BibTeX
Article Data Visualization using Linear and Non-linear Dimensionality Reduction Methods Kim, J., Youn, J. {Journal of the Korea Society of Computer and Information}, 23(12):21-26, 2018
{As the large amount of data can be efficiently stored, the methods extracting meaningful features from big data has become important. Especially, the techniques of converting high- to low-dimensional data are crucial for the \textquoterightData visualization\textquoteright. In this study, principal component analysis (PCA; linear dimensionality reduction technique) and Isomap (non-linear dimensionality reduction technique) are introduced and applied to neural big data obtained by the functional magnetic resonance imaging (fMRI). First, we investigate how much the physical properties of stimuli are maintained after the dimensionality reduction processes. We moreover compared the amount of residual variance to quantitatively compare the amount of information that was not explained. As result, the dimensionality reduction using Isomap contains more information than the principal component analysis. Our results demonstrate that it is necessary to consider not only linear but also nonlinear characteristics in the big data analysis.}
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Miscellaneous Decoding the direction of implied motion in human early visual cortex Altan, G., Bartels, A. 48th Annual Meeting of the Society for Neuroscience (Neuroscience 2018), 2018
{Implied motion perception is a striking case of our capacity to infer motion features from static pictures that imply movement. At a higher, cognitive level, the mere configuration of an object (such as a snapshot of a walking human) can imply motion in a directional way. Previous studies have shown that implied motion processing recruits direction selective neurons and activates cortical motion processing regions. However, it is unknown whether object-processing regions or early visual regions are involved in implied motion processing. In the present study we used fMRI and multivariate pattern classification to examine which human brain regions differentiate implicit direction information in static images of implied motion. We hence examined BOLD ac­tivity patterns within independently defined early visual (V1-V3), motion (V5+/MT+) and object-processing (LO1, LO2) regions when participants viewed still images with directional implied motion (rightward vs. leftward). The stimuli contained both animate (birds) and inanimate (airplanes, cars) objects as sources of implied motion. The objects were presented at the center of the visual field on a horizontally blurred background in the periphery. We found that response patterns in visual areas V2, V3, human motion complex V5+/MT+, and object responsive region LO2 coded for the direction of the implied motion stimuli significantly better than chance. Decoding in visual areas V1 and LO1 was at chance level. We then examined decoding in retinotopically defined foveal and peripheral representations of V1-V3. Only the foveal representation was stimulated by the foreground objects, the periphery by blurred background. We found that peripheral V1-V3 allowed decoding of implied motion directions, while foveal representations did not. Hence, high-level information of implied motion directionality is represented in peripheral V1-V3, i.e. regions that were never given the information through bottom-up stimulation. This suggests that higher-level cognitive processes (potentially based in LO2, V5+/MT+) detect implied motion direction based on object configuration and feed it back to cover the peripheral context in early visual cortex, potentially encoding expected background-motion. The results provide direct evidence for information in early visual cortex originating from feedback, compatible with predictive coding theory.}
BibTeX
Article Decoding visual roughness perception: an fMRI study Kim, J., Bülthoff, I., Bülthoff, H. {Somatosensory \& Motor Research}, 35(3-4):212-217, 2018
{The neural substrates of tactile roughness perception have been investigated by many neuroimaging studies, while relatively little effort has been devoted to the investigation of neural representations of visually perceived roughness. In this human fMRI study, we looked for neural activity patterns that could be attributed to five different roughness intensity levels when the stimuli were perceived visually, i.e., in absence of any tactile sensation. During functional image acquisition, participants viewed video clips displaying a right index fingertip actively exploring the sandpapers that had been used for the behavioural experiment. A whole brain multivariate pattern analysis found four brain regions in which visual roughness intensities could be decoded: the bilateral posterior parietal cortex (PPC), the primary somatosensory cortex (S1) extending to the primary motor cortex (M1) in the right hemisphere, and the inferior occipital gyrus (IOG). In a follow-up analysis, we tested for correlations between the decoding accuracies and the tactile roughness discriminability obtained from a preceding behavioural experiment. We could not find any correlation between both although, during scanning, participants were asked to recall the tactilely perceived roughness of the sandpapers. We presume that a better paradigm is needed to reveal any potential visuo-tactile convergence. However, the present study identified brain regions that may subserve the discrimination of different intensities of visual roughness. This finding may contribute to elucidate the neural mechanisms related to the visual roughness perception in the human brain.}
DOI BibTeX
Article Decoupling of a double-row 16-element tight-fit transceiver phased array for human whole-brain imaging at 9.4 T Avdievich, N., Giapitzakis, I., Pfrommer, A., Shajan, G., Scheffler, K., Henning, A. {NMR in Biomedicine}, 31(9):1-13, Heyden & Son, London, 2018
{One of the major challenges in constructing multi-channel and multi-row transmit (Tx) or transceiver (TxRx) arrays is the decoupling of the array\textquotesingles loop elements. Overlapping of the surface loops allows the decoupling of adjacent elements and also helps to improve the radiofrequency field profile by increasing the penetration depth and eliminating voids between the loops. This also simplifies the design by reducing the number of decoupling circuits. At the same time, overlapping may compromise decoupling by generating high resistive (electric) coupling near the overlap, which cannot be compensated for by common decoupling techniques. Previously, based on analytical modeling, we demonstrated that electric coupling has strong frequency and loading dependence, and, at 9.4 T, both the magnetic and electric coupling between two heavily loaded loops can be compensated at the same time simply by overlapping the loops. As a result, excellent decoupling was obtained between adjacent loops of an eight-loop single-row (1 $\times$ 8) human head tight-fit TxRx array. In this work, we designed and constructed a 9.4-T (400-MHz) 16-loop double-row (2 $\times$ 8) overlapped TxRx head array based on the results of the analytical and numerical electromagnetic modeling. We demonstrated that, simply by the optimal overlap of array loops, a very good decoupling can be obtained without additional decoupling strategies. The constructed TxRx array provides whole-brain coverage and approximately 1.5 times greater Tx efficiency relative to a transmit-only/receive-only (ToRo) array, which consists of a larger Tx-only array and a nested tight-fit 31-loop receive (Rx)-only array. At the same time, the ToRo array provides greater peripheral signal-to-noise ratio (SNR) and better Rx parallel performance in the head\textendashfeet direction. Overall, our work provides a recipe for a simple, robust and very Tx-efficient design suitable for parallel transmission and whole-brain imaging at ultra-high fields.}
DOI BibTeX
Article Decoupling of a tight-fit transceiver phased array for human brain imaging at 9.4T: Loop overlapping rediscovered Avdievich, N., Giapitzakis, I., Pfrommer, A., Henning, A. {Magnetic Resonance in Medicine}, 79(2):1200-1211, 2018
{Purpose To improve the decoupling of a transceiver human head phased array at ultra-high fields (UHF, $\geq$ 7T) and to optimize its transmit (Tx) and receive (Rx) performance, a single-row eight-element (1 $\times$ 8) tight-fit transceiver overlapped loop array was developed and constructed. Overlapping the loops increases the RF field penetration depth but can compromise decoupling by generating substantial mutual resistance. Methods Based on analytical modeling, we optimized the loop geometry and relative positioning to simultaneously minimize the resistive and inductive coupling and constructed a 9.4T eight-loop transceiver head phased array decoupled entirely by overlapping loops. Results We demonstrated that both the magnetic and electric coupling between adjacent loops is compensated at the same time by overlapping and nearly perfect decoupling (below -30 dB) can be obtained without additional decoupling strategies. Tx-efficiency and SNR of the overlapped array outperformed that of a common UHF gapped array of similar dimensions. Parallel Rx-performance was also not compromised due to overlapping the loops. Conclusion As a proof of concept we developed and constructed a 9.4T (400 MHz) overlapped transceiver head array based on results of the analytical modeling. We demonstrated that at UHF overlapping loops not only provides excellent decoupling but also improves both Tx- and Rx-performance.}
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Miscellaneous Deep CEST MRI: 9.4T spectral super-resolution from 3T CEST MRI data Zaiss, M., Deshmane, A., Herz, K., Braun, M., Bender, B., Lindig, T., Scheffler, K. Joint Annual Meeting ISMRM-ESMRMB 2018, 2018
{CEST peaks are easy to detect at ultra-high-field strengths due to high signal and spectral separation. However, spectral coalescence and line broadening makes modeling of CEST effects at clinical field strengths (\textless\textequals3T) a challenge. In this proof-of-concept study of super-resolution CEST imaging, the underlying spectral features of 3T Z-spectra were predicted using a neural network trained on 9.4T data. Applying the neural network to untrained volunteer and patient data acquired at 3T resulted in the expected contrast in healthy gray and white matter and tumor tissue in Z-spectra and APT, NOE, and MT CEST maps.}
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Conference Paper Deep Neural Network-Based Cooperative Visual Tracking Through Multiple Micro Aerial Vehicles Price, E., Lawless, G., Ludwig, R., Martinović, I., Bülthoff, H., Black, M., Ahmad, A. In {IEEE Robotics and Automation Letters}, 3:3193-3200, IEEE, Madrid, Spain, 2018
{Multi-camera tracking of humans and animals in outdoor environments is a relevant and challenging problem. Our approach to it involves a team of cooperating micro aerial vehicles (MAVs) with on-board cameras only. Deep neural networks (DNNs) often fail at detecting small-scale objects or those that are far away from the camera, which are typical characteristics of a scenario with aerial robots. Thus, the core problem addressed in this paper is how to achieve on-board, online, continuous and accurate vision-based detections using DNNs for visual person tracking through MAVs. Our solution leverages cooperation among multiple MAVs and active selection of most informative regions of image. We demonstrate the efficiency of our approach through simulations with up to 16 robots and real robot experiments involving two aerial robots tracking a person, while maintaining an active perception-driven formation. ROS-based source code is provided for the benefit of the community.}
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Article Delayed increase of thrombocyte levels after a single sub-anesthetic dose of ketamine: A randomized trial Colic, M., Woelfer, L., Colic, M., Leutritz, A., Liebe, T., Fensky, L., Sen, Z., Li, M., Hoffmann, J., Kretzschmar, M., Isermann, B., Walter, M. {European Neuropsychopharmacology}, 28(6):701-709, Elsevier, Amsterdam, 2018
{Recently, ketamine has been investigated as a potential antidepressant option for treatment resistant depression. Unlike traditional drugs, it yields immediate effects, most likely via increased glutamatergic transmission and synaptic plasticity. However, ketamine administration in humans is systemic and its long\textendashterm impact on blood parameters has not yet been described in clinical studies. Here we investigated potential sustained effects of ketamine administration (0.5 mg/kg ketamine racemate) on hematological and biochemical values in plasma and serum in a randomized double\textendashblinded study. 80 healthy young participants were included and whole blood samples were collected 5 days before, and 14 days after the infusion. To assess the group effect, repeated measure analyses of co\textendashvariance (rmANCOVA) were conducted for the following blood parameters: levels of sodium, potassium, calcium, hemoglobin and number of erythrocytes, lymphocytes, and thrombocytes. RmANCOVA revealed a significant time by treatment effect on thrombocyte levels (F1, 74 \textequals 13.54, p \textless 0.001, eta \textequals 0.155), driven by an increase in the ketamine group (paired t-test, t \textequals \textminus3.51, df \textequals 38, p \textequals 0.001). Specificity of thrombocyte effect was confirmed by logistic regression, and in addition, no other coagulation parameters showed significant interaction. Moreover, the relative increase in the ketamine group was stable across sexes and not predicted by age, BMI, smoking, alcohol or drug use, and contraception. Our results describe aftereffects of sub\textendashanesthetic ketamine administration on blood coagulation parameters, which should be considered especially when targeting psychiatric populations with relevant clinical comorbidities.}
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Conference Paper Design Guidelines for Reliability Communication in Autonomous Vehicles Faltaous, S., Baumann, M., Schneegass, S., Chuang, L. In AutomotiveUI \textquotesingle18: Proceedings of the 10th International Conference on Automotive User Interfaces and Interactive Vehicular Applications, 258-267, ACM Press, Toronto, ON, Canada, 2018 DOI BibTeX
Modern Magnetic Systems Article Deterministic creation and deletion of a single magnetic skyrmion observed by direct time-resolved X-ray microscopy Woo, S., Song, K. M., Zhang, X., Ezawa, M., Zhou, Y., Liu, X., Weigand, M., Finizio, S., Raabe, J., Park, M., Lee, K., Choi, J. W., Min, B., Koo, H. C., Chang, J. {Nature Electronics}, 1(5):288-296, Springer Nature, London, 2018 DOI BibTeX
Miscellaneous Differentiating between models of perceptual decision- making using pupil-size inferred confidence Kawaguchi, K. 19th Conference of Junior Neuroscientists of Tübingen (NeNa 2018), 2018 BibTeX
Modern Magnetic Systems Article Direct observation of Zhang-Li torque expansion of magnetic droplet solitons Chung, S., Tuan Le, Q., Ahlberg, M., Awad, A. A., Weigand, M., Bykova, I., Khymyn, R., Dvornik, M., Mazraati, H., Houshang, A., Jiang, S., Nguyen, T. N. A., Goering, E., Schütz, G., Gräfe, J., Åkerman, J. {Physical Review Letters}, 120(21), American Physical Society, Woodbury, N.Y., 2018
Magnetic droplets are nontopological dynamical solitons that can be nucleated in nanocontact based spin torque nano-oscillators (STNOs) with perpendicular magnetic anisotropy free layers. While theory predicts that the droplet should be of the same size as the nanocontact, its inherent drift instability has thwarted attempts at observing it directly using microscopy techniques. Here, we demonstrate highly stable magnetic droplets in all-perpendicular STNOs and present the first detailed droplet images using scanning transmission X-ray microscopy. In contrast to theoretical predictions, we find that the droplet diameter is about twice as large as the nanocontact. By extending the original droplet theory to properly account for the lateral current spread underneath the nanocontact, we show that the large discrepancy primarily arises from current-in-plane Zhang-Li torque adding an outward pressure on the droplet perimeter. Electrical measurements on droplets nucleated using a reversed current in the antiparallel state corroborate this picture.
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Modern Magnetic Systems Conference Paper Direct observations of sub-100 nm spin wave propagation in magnonic wave-guides Träger, N., Gruszecki, P., Lisiecki, F., Förster, J., Weigand, M., Kuswik, P., Dubowik, J., Schütz, G., Krawczyk, M., Gräfe, J. In 2018 IEEE International Magnetics Conference (INTERMAG 2018), IEEE, Singapore, 2018 DOI BibTeX
Article Disruption of neurite morphology parallels MS progression Spanò, B., Giuletti, G., Pisani, V., Morreale, M., Tuzzi, E., Nocentini, U., Francia, A., Caltagirone, C., Bozzali, M., Cercignani, M. {Neurology: Neuroimmunology \& Neuroinflammation}, 5(6):1-11, 2018
{Objectives: To apply advanced diffusion MRI methods to the study of normal-appearing brain tissue in MS and examine their correlation with measures of clinical disability. Methods: A multi-compartment model of diffusion MRI called neurite orientation dispersion and density imaging (NODDI) was used to study 20 patients with relapsing-remitting MS (RRMS), 15 with secondary progressive MS (SPMS), and 20 healthy controls. Maps of NODDI were analyzed voxel-wise to assess the presence of abnormalities within the normal-appearing brain tissue and the association with disease severity. Standard diffusion tensor imaging (DTI) parameters were also computed for comparing the 2 techniques. Results: Patients with MS showed reduced neurite density index (NDI) and increased orientation dispersion index (ODI) compared with controls in several brain areas (p \textless 0.05), with patients with SPMS having more widespread abnormalities. DTI indices were also sensitive to some changes. In addition, patients with SPMS showed reduced ODI in the thalamus and caudate nucleus. These abnormalities were associated with scores of disease severity (p \textless 0.05). The association with the MS functional composite score was higher in patients with SPMS compared with patients with RRMS. Conclusions: NODDI and DTI findings are largely overlapping. Nevertheless, NODDI helps interpret previous findings of increased anisotropy in the thalamus of patients with MS and are consistent with the degeneration of selective axon populations.}
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Article Dissecting the Synapse- and Frequency-Dependent Network Mechanisms of In Vivo Hippocampal Sharp Wave-Ripples Ramirez-Villegas, J., Willeke, K., Logothetis, N., Besserve, M. {Neuron}, 100(5):1224-1240, Cell Press, Cambridge, Mass., 2018
{Hippocampal ripple oscillations likely support reactivation of memory traces that manifest themselves as temporally organized spiking of sparse neuronal ensembles. However, the network mechanisms concurring to achieve this function are largely unknown. We designed a multi-compartmental model of the CA3-CA1 subfields to generate biophysically realistic ripple dynamics from the cellular level to local field potentials. Simulations broadly parallel in vivo observations and support that ripples emerge from CA1 pyramidal spiking paced by recurrent inhibition. In addition to ripple oscillations, key coordination mechanisms involve concomitant aspects of network activity. Recurrent synaptic interactions in CA1 exhibit slow-gamma band coherence with CA3 input, thus offering a way to coordinate CA1 activities with CA3 inducers. Moreover, CA1 feedback inhibition controls the content of spontaneous replay during CA1 ripples, forming new mnemonic representations through plasticity. These insights are consistent with slow-gamma interactions and interneuronal circuit plasticity observed in vivo, suggesting a multifaceted ripple-related replay phenomenon.}
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Miscellaneous Distinct activity patterns in neuromodulatory centers are associated with differential modulation of cortical low and high gamma oscillations Totah, N., van Keulen, S., Logothetis, N., Eschenko, O. AREADNE 2018: Research in Encoding And Decoding of Neural Ensembles, 102, AREADNE Foundation, Cambridge, MA, USA, 2018
{Neuromodulatory systems are thought to gate cortical neuronal excitability \textemdash a generalized state consisting of high frequency (20\textendash200 Hz) local field potential (LFP) oscillations. Stimulating neuromodulatory centers evokes a non-specific response across all components of the excited cortical state (beta and gamma band LFP oscillations). The non-specificity of neuromodulation is at odds with the fact that neuromodulators regulate distinct cognitive functions that are affliated with different cortical LFP oscillations. For example, various dopamine and norepinephrine-dependent cognitive functions (e.g., working memory, spatial navigation, and top-down attention) are each accompanied by power increases within different LFP frequency bands. How can neuromodulators contribute to cognitive processes associated with different LFP frequency bands if they non-specifically modulate cortical LFP? Here, rather than perturbing neuromodulatory systems with stimulation, we recorded spontaneous unit activity from two primary sources of cortical neuromodulators (the noradrenergic locus coeruleus, LC, and dopaminergic ventral tegmental area, VTA) and correlated it with LFP power fluctuations in the prefrontal, visual, and somatosensory cortex of urethaneanesthetized rats. We found that neuromodulatory population spike rate rhythmically fluctuates at 1\textendash2 Hz (delta band) in both LC and VTA. But, in the LC, an additional 5\textendash7 Hz (theta band) fluctuation of spike rate occurred. While neuromodulatory delta oscillations non-specifically regulated the power of all cortical LFP oscillations over 20 Hz, theta spike rate oscillations were exclusively associated with cortical high gamma band (60\textendash200 Hz) activity. As LC population spiking rhythmically rose and fell, two types of LC single units (characterized by narrow or wide action potentials) fired in phasic opposition, potentially providing differential cortical state regulation. Our results demonstrate that the noradrenergic system is a unique neuromodulatory center that can affect specific cortical activity patterns, rather than merely gate a generalized state of cortical excitability.}
BibTeX
Miscellaneous Distinct activity patterns in neuromodulatory centers are associated with differential modulation of cortical low and high gamma oscillations Totah, N., van Keulen, S., Logothetis, N., Eschenko, O. 48th Annual Meeting of the Society for Neuroscience (Neuroscience 2018), 2018
{Neuromodulatory systems are thought to gate cortical neuronal excitability \textendash a generalized state consisting of high frequency (20 to 200 Hz) local field potential (LFP) oscillations. Stimulating neuromodulatory centers evokes a non-specific response across all components of the excited cortical state (beta and gamma band LFP oscillations). The non-specificity of neuromodulation is at odds with the fact that neuromodulators regulate distinct cognitive functions that are affiliated with different cortical LFP oscillations. For example, various dopamine and norepinephrine-dependent cognitive functions (e.g., working memory, spatial navigation, and top-down attention) are each accompanied by power increases within different LFP frequency bands. How can neuromodulators contribute to cognitive processes associated with different LFP frequency bands if they non-specifically modulate cortical LFP? Here, rather than perturbing neuromodulatory systems with stimulation, we recorded spontaneous unit activity from two primary sources of cortical neuromodulators (the noradrenergic locus coeruleus, LC, and dopaminergic ventral tegmental area, VTA) and correlated it with LFP power fluctuations in the prefrontal, visual, and somatosensory cortex of urethane-anesthetized rats. We found that neuromodulatory population spike rate rhythmically fluctuates at 1 \textendash 2 Hz (delta band) in both LC and VTA. But, in the LC, an additional 5 \textendash 7 Hz (theta band) fluctuation of spike rate occurred. While neuromodulatory delta oscillations non-specifically regulated the power of all cortical LFP oscillations over 20 Hz, theta spike rate oscillations were exclusively associated with cortical high gamma band (60 \textendash 200 Hz) activity. As LC population spiking rhythmically rose and fell, two types of LC single units (characterized by narrow or wide action potentials) fired in phasic opposition, potentially providing differential cortical state regulation. Our results demonstrate that the noradrenergic system is a unique neuromodulatory center that can affect specific cortical activity patterns, rather than merely gate a generalized state of cortical excitability.}
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Article Dopamine Is Signaled by Mid-frequency Oscillations and Boosts Output Layers Visual Information in Visual Cortex Zaldivar, D., Goense, J., Lowe, S., Logothetis, N., Panzeri, S. {Current Biology}, 28(2):224-235, 2018
{Neural oscillations are ubiquitously observed in cortical activity, and are widely believed to be crucial for mediating transmission of information across the cortex. Yet, the neural phenomena contributing to each oscillation band, and their effect on information coding and transmission, are largely unknown. Here, we investigated whether individual frequency bands specifically reflect changes in the concentrations of dopamine, an important neuromodulator, and how dopamine affects oscillatory information processing. We recorded the local field potential (LFP) at different depths of primary visual cortex (V1) in anesthetized monkeys (Macaca mulatta) during spontaneous activity and during visual stimulation with Hollywood movie clips while pharmacologically mimicking dopaminergic neuromodulation by systemic injection of L-DOPA (a metabolic precursor of dopamine). We found that dopaminergic neuromodulation had marked effects on both spontaneous and movie-evoked neural activity. During spontaneous activity, dopaminergic neuromodulation increased the power of the LFP specifically in the [19\textendash38 Hz] band, suggesting that the power of endogenous visual cortex oscillations in this band can be used as a robust marker of dopaminergic neuromodulation. Moreover, dopamine increased visual information encoding over all frequencies during movie stimulation. The information increase due to dopamine was prominent in the supragranular layers of cortex that project to higher cortical areas and in the gamma [50\textendash100 Hz] band that has been previously implicated in mediating feedforward information transfer. These results thus individuate new neural mechanisms by which dopamine may promote the readout of relevant sensory information by strengthening the transmission of information from primary to higher areas.}
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Article Dose-Dependent Effects of Intranasal Insulin on Resting-State Brain Activity Kullmann, S., Veit, R., Peter, A., Pohmann, R., Scheffler, K., Häring, H., Fritsche, A., Preissl, H., Heni, M. {Journal of Clinical Endocrinology and Metabolism}, 103(1):253-262, Issued for the Endocrine Society by the Williams & Wilkins Co., Baltimore, Md., 2018
{Context Insulin action in the human brain influences eating behavior, cognition, and whole-body metabolism. Studies investigating brain insulin rely on intranasal application. Objective To investigate effects of three doses of insulin and placebo as nasal sprays on the central and autonomous nervous system and analyze absorption of insulin into the bloodstream. Design, participants and methods Nine healthy men received placebo, 40U, 80U and 160U insulin spray in randomized order. Before and after spray, brain activity was assessed by functional magnetic resonance imaging and heart rate variability (HRV) was assessed from ECG. Plasma insulin, C-peptide, and glucose were measured regularly. Results Nasal insulin administration dose-dependently modulated regional brain activity and the normalized high-frequency component of the HRV. Post-hoc analyses revealed that only 160U insulin showed a significant difference from placebo. Dose-dependent spill-over of nasal insulin into the bloodstream was detected. The brain response was not correlated with this temporary rise in circulating insulin. Conclusions Nasal insulin dose-dependently modulated regional brain activity with the strongest effects after 160 U. However, this dose was accompanied by a transient increase in circulating insulin concentrations due to a spillover into circulation. Our current results may serve as a basis for future studies with nasal insulin to untangle brain insulin effects in health and disease.}
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Conference Paper Driving Simulators with Hexapod Motion System: Adding a Yaw Turntable Olivari, M., Drop, F., Katliar, M., Bülthoff, H. In DSC 2018 EUROPE VR Driving Simulation Conference & Exhibition, 121-122, Driving Simulation Association, Antibes, France, 2018 BibTeX
Article Dual-frequency irradiation CEST-MRI of endogenous bulk mobile proteins Goerke, C., Breitling, J., Zaiss, M., Windschuh, J., Kunz, P., Schuenke, P., Paech, D., Longo, D., Klika, K., Ladd, M., Bachert, P. {NMR in Biomedicine}, 31(6):1-14, 2018
{A novel MRI contrast is proposed which enables the selective detection of endogenous bulk mobile proteins in vivo. Such a non-invasive imaging technique may be of particular interest for many diseases associated with pathological alterations of protein expression, such as cancer and neurodegenerative disorders. Specificity to mobile proteins was achieved by the selective measurement of intramolecular spin diffusion and the removal of semi-solid macromolecular signal components by a correction procedure. For this purpose, the approach of chemical exchange saturation transfer (CEST) was extended to a radiofrequency (RF) irradiation scheme at two different frequency offsets (dualCEST). Using protein model solutions, it was demonstrated that the dualCEST technique allows the calculation of an image contrast which is exclusively sensitive to changes in concentration, molecular size and the folding state of mobile proteins. With respect to application in humans, dualCEST overcomes the selectivity limitations at relatively low magnetic field strengths, and thus enables examinations on clinical MR scanners. The feasibility of dualCEST examinations in humans was verified by a proof-of-principle examination of a brain tumor patient at 3 T. With its specificity for the mobile fraction of the proteome, its comparable sensitivity to conventional water proton MRI and its applicability to clinical MR scanners, this technique represents a further step towards the non-invasive imaging of proteomic changes in humans.}
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Article Dynamic B 0 shimming of the human brain at 9.4 T with a 16-channel multi-coil shim setup Aghaeifar, A., Mirkes, C., Bause, J., Steffen, T., Avdievitch, N., Henning, A., Scheffler, K. {Magnetic Resonance in Medicine}, 80(4):1714-1725, Wiley-Liss, New York, 2018
{Purpose A 16-channel multi-coil shimming setup was developed to mitigate severe B0 field perturbations at ultrahigh field and improve data quality for human brain imaging and spectroscopy. Methods The shimming setup consisted of 16 circular B0 coils that were positioned symmetrically on a cylinder with a diameter of 370 mm. The latter was large enough to house a shielded 18/32-channel RF transceiver array. The shim performance was assessed via simulations and phantom as well as in vivo measurements at 9.4 T. The global and dynamic shimming performance of the multi-coil setup was compared with the built-in scanner shim system for EPI and single voxel spectroscopy. Results The presence of the multi-coil shim did not influence the performance of the RF coil. The performance of the proposed setup was similar to a full third-order spherical harmonic shim system in the case of global static and dynamic slice-wise shimming. Dynamic slice-wise shimming with the multi-coil setup outperformed global static shimming with the scanner\textquotesingles second-order spherical-harmonic shim. The multi-coil setup allowed mitigating geometric distortions for EPI. The combination of the multi-coil shim setup with the zeroth and first-order shim of the scanner further reduced the standard deviation of the B0 field in the brain by 12 compared with the case in which multi-coil was used exclusively. Conclusion The combination of a multi-coil setup and the linear shim channels of the scanner provides a straightforward solution for implementing dynamic slice-wise shimming without requiring an additional pre-emphasis setup.}
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Miscellaneous Dynamic B0 Shimming for Multi-Slice Metabolite Mapping at Ultra-High Field in the Human Brain: Very High Order Spherical Harmonics vs. Multi-Coil Chang, P., Nassirpour, S., Aghaeifar, A., Scheffler, K., Henning, A. Joint Annual Meeting ISMRM-ESMRMB 2018, 2018
{In this work, we evaluated the performance of two B0 shimming approaches (i.e. a very high order spherical harmonic shim system versus a multi-coil shim setup), for dynamic shimming in the context of high resolution and multi-slice metabolite mapping of the human brain at 9.4T.}
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Modern Magnetic Systems Article Dynamic Janus metasurfaces in the visible spectral region Yu, P., Li, J., Zhang, S., Jin, Z., Schütz, G., Qiu, C., Hirscher, M., Liu, N. {Nano Letters}, 18(7):4584-4589, American Chemical Society, Washington, DC, 2018 DOI BibTeX
Miscellaneous Dynamic glucose-enhanced MRI: clinical perspectives and challenges Paech, D., Schuenke, P., Köhler, C., Bachert, P., Ladd, M., Bendszus, M., Schlemmer, H., Zaiss, M., Radbruch, A. {Insights into Imaging}, 9:S265, 2018
{Purpose: To investigate dynamic glucose-enhanced (DGE) magnetic resonance imaging (MRI) at 7 Tesla (7T) in the healthy human brain and newly diagnosed untreated glioblastoma patients. Methods and Materials: Eleven newly diagnosed glioblastoma patients and eight healthy volunteers were included in this prospective ethic approved study. DGE MRI was performed at a 7T whole-body scanner (Siemens,Healthcare,Erlangen,Germany) using an in-house developed adiabatically-prepared chemical exchange sensitive spin-lock (CESL) sequence (temporal resolution \textequals 7 sec). 100ml of 20\textpercent D-glucose were injected intravenously during DGE MRI. Gadolinium contrast-enhanced T1-w images were obtained along the clinical standard MRI protocol at 3T. Mean signal intensities of (1)the tumor regions vs. normal appearing white matter, and (2)gray matter vs. white matter, were compared by using the Student\textquotesingles t-test. Results: No adverse effects were observed in patients and volunteers related to glucose injections. The DGE contrast allowed for the identification of pathophysiologically increased glucose uptake in the tumor area in all patients. The mean signal intensity of the glucose enhancing tumor region over all patients (DGE$\varrho$\textequals3.57$\pm$1.79\textpercent) was significantly higher than in contralateral normal appearing white matter (DGE$\varrho$\textequals0.22$\pm$0.80\textpercent) (p\textless0.01). Futher, DGE MRI revealed an increased glucose uptake in gray matter regions compared to white matter of the normal human brain (p\textless0.001). Conclusion: DGE MRI may provide complementary information about the metabolic heterogeneity of tumors, with implications for biopsy targeting, patient therapy and response monitoring. Furthermore, glucose enhanced MRI could open up the field of metabolic imaging without the limitations set by ionizing radiation and high expenses associated with radioisotopes.}
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Article Effects of Cable Sway, Electrode Surface Area, and Electrode Mass on Electroencephalography Signal Quality during Motion Symeonidou, E., Nordin, A., Hairston, W., Ferris, D. {Sensors}, 18(4):1-13, MDPI, 2018
{More neuroscience researchers are using scalp electroencephalography (EEG) to measure electrocortical dynamics during human locomotion and other types of movement. Motion artifacts corrupt the EEG and mask underlying neural signals of interest. The cause of motion artifacts in EEG is often attributed to electrode motion relative to the skin, but few studies have examined EEG signals under head motion. In the current study, we tested how motion artifacts are affected by the overall mass and surface area of commercially available electrodes, as well as how cable sway contributes to motion artifacts. To provide a ground-truth signal, we used a gelatin head phantom with embedded antennas broadcasting electrical signals, and recorded EEG with a commercially available electrode system. A robotic platform moved the phantom head through sinusoidal displacements at different frequencies (0\textendash2 Hz). Results showed that a larger electrode surface area can have a small but significant effect on improving EEG signal quality during motion and that cable sway is a major contributor to motion artifacts. These results have implications in the development of future hardware for mobile brain imaging with EEG.}
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Article Effects of visual stimulus characteristics and individual differences in heading estimation de Winkel, K., Kurtz, M., Bülthoff, H. {Journal of Vision}, 18(11):1-17, Scholar One, Inc., Charlottesville, VA, 2018
{Visual heading estimation is subject to periodic patterns of constant (bias) and variable (noise) error. The nature of the errors, however, appears to differ between studies, showing underestimation in some, but overestimation in others. We investigated whether field of view (FOV), the availability of binocular disparity cues, motion profile, and visual scene layout can account for error characteristics, with a potential mediating effect of vection. Twenty participants (12 females) reported heading and rated vection for visual horizontal motion stimuli with headings ranging the full circle, while we systematically varied the above factors. Overall, the results show constant errors away from the fore-aft axis. Error magnitude was affected by FOV, disparity, and scene layout. Variable errors varied with heading angle, and depended on scene layout. Higher vection ratings were associated with smaller variable errors. Vection ratings depended on FOV, motion profile, and scene layout, with the highest ratings for a large FOV, cosine-bell velocity profile, and a ground plane scene rather than a dot cloud scene. Although the factors did affect error magnitude, differences in its direction were observed only between participants. We show that the observations are consistent with prior beliefs that headings align with the cardinal axes, where the attraction of each axis is an idiosyncratic property.}
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Miscellaneous Egocentric Anisotropy in the Representation of Horizontal and Vertical Traveled Distance Hinterecker, T., Pretto, P., de Winkel, K., Karnath, H., Bülthoff, H. 11th International Conference on Spatial Cognition (SC 2018), 2018 BibTeX
Miscellaneous Eigenvector centrality mapping for ultrahigh resolution fMRI data of the human brain Lohmann, G., Loktyushin, A., Stelzer, J., Scheffler, K. 2018
{Eigenvector centrality mapping (ECM) is a popular technique for analyzing fMRI data of the human brain. It is used to obtain maps of functional hubs in networks of the brain in a manner similar to Google\textquotesingles PageRank algorithm. ECM attributes a score to the time course of each voxel that reflects its centrality within the network. Voxels that are strongly correlated with many other voxels that are themselves strongly correlated with other voxels receive high scores. Currently, there exist two different implementations ECM, one of which is very fast but limited to one particular type of correlation metric whose interpretation can be problematic. The second implementation supports many different metrics, but it is computationally costly and requires a very large main memory. Here we propose two new implementations of the ECM approach that resolve these issues. The first is based on a new correlation metric that we call "ReLU correlation (RLC)". The second method is based on matrix projections. We demonstrate the use of both techniques on standard fMRI data, as well as on high-resolution fMRI data acquired at 9.4 Tesla.}
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Modern Magnetic Systems Miscellaneous Emission and propagation of multi-dimensional spin waves in anisotropic spin textures Sluka, V., Schneider, T., Gallardo, R. A., Kakay, A., Weigand, M., Warnatz, T., Mattheis, R., Roldan-Molina, A., Landeros, P., Tiberkevich, V., Slavin, A., Schütz, G., Erbe, A., Deac, A., Lindner, J., Raabe, J., Fassbender, J., Wintz, S. 2018 URL BibTeX
Conference Paper Ensembles of networks drastically increase dynamic range Zierenberg, J., Wilting, J., Priesemann, V., Levina, A. In Bernstein Conference 2018, Berlin, Germany, 2018, Bernstein Conference 2018
Living organisms are constantly exposed to a huge range of sensory stimuli. The ability of an organism to cope with the variability of inputs determines how well they thrive. One measure for the capability of a system to distinguish stimuli is the dynamic range. It was shown in theory and experiments that the dynamic range is maximized close to a non-equilibrium phase transition (NEPT)[1,2]. A tractable model that shows such a NEPT and describes activity propagation is the branching network with control parameter m. In this model the dynamic range is indeed maximal at the NEPT (m{\textequals}1). However, for small deviations from the NEPT, as observed for cortex in vivo [3], the dynamic range is virtually indistinguishable from the optimal one and covers the same interval of stimuli (discriminable interval, Fig. 1A). We identify this to be a result from convergence effects in the branching network, i.e., the simultaneous transmission of activation to the same unit from multiple sources in the system. When we correct for convergences in the model using biologically plausible adaptation, the discriminable interval becomes a function of m (Fig. 1B). Considering an ensemble of such networks enables us to extend the discriminable interval and realize a diverging dynamic range in the limit of an infinite ensemble of networks. The same effect can be achieved by rapidly adapting the control parameter of the modified model to the intensity of the incoming stimuli. Our results allow to dissect the mechanisms of sensitivity optimization. They can be applied for better understanding of biological networks as well as to optimize machine learning algorithms.
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Miscellaneous Entwicklung der funktionellen Bildgebung in den Neurowissenschaften Grodd, W. Psychiatrie: Biologie, Psyche, Verantwortung "Die spannendste Disziplin": Symposium für Prof. Dr. Dr. Frank Schneider, 2018 BibTeX
Miscellaneous Estimating average single neuron receptive field sizes in human primary visual cortex Keliris, G., Li, Q., Papanikolaou, A., Logothetis, N., Smirnakis, S. AREADNE 2018: Research in Encoding And Decoding of Neural Ensembles, 71, AREADNE Foundation, Cambridge, MA, USA, 2018
{The retinotopic organization of visual cortex has been extensively studied in primates and other mammals with the notion of the receptive field (RF) playing a major contribution to neuroscientific research in general. Although a wealth of information has been acquired from studies in cats, non-human primates, et cetera, which led to explicit understanding of the organization of primary visual cortex and the development of analytical formulations to describe the projection from the retina to the cortical space, RF sizes have not been accurately estimated in human V1. Recent studies substantially advanced this field of research by using novel neuro-computational methods. A prime example of such methods is the estimation of population receptive fields (pRFs) in retinotopically organized visual areas. However, pRFs are only estimates of aggregate voxel-based averages of ten to hundreds of thousands of neurons within fMRI voxels and are a function of: (a) the receptive field properties of single units belonging to a voxel, (b) the scatter in the location of receptive field centres across units, and (c) the interactions between nearby connected units. Here, we present a novel approach to estimate the average single-neuron receptive field sizes in human primary visual cortex. To this end, we exploit the spatial-frequency dependent fMRI responses of visual RFs modeled as Gabor functions. Furthermore, we validate non-invasive RF size estimates obtained using the same fMRI method in non-human primates by comparing them directly with RF sizes obtained via intracranial electrophysiological recordings.}
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Miscellaneous Estimation of T2 Relaxation Times of Downfield Peaks in Human Brain at 9.4 T Murali Manohar, S., Borbath, T., Fichtner, N., Giapitzakis, I., Zaldivar, D., Kreis, R., Henning, A. Joint Annual Meeting ISMRM-ESMRMB 2018, 2018
{T2 relaxations times for the downfield metabolites in human brain 1H MR spectra were estimated at 9.4 T. A possible new peak at 8.35 ppm with rapid T2 decay is reported. Due to the use of a non-water suppressed MRS method, the T2 of slowly exchanging peaks could be assessed. The shorter T2 relaxation times in the downfield compared to the upfield spectral areas leads us to suspect a macromolecular contribution, while also exchange effects may contribute to the short apparent T2s.}
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Miscellaneous Estimation of Tp2 Relaxation Times of Macromolecules in Human Brain Spectra at 9.4 T Borbath, T., Murali Manohar, S., Henning, A. MRS Workshop 2018 Metabolic Imaging, 2018
{Previous studies have shown, that the inclusion of a macromolecular baseline in the basis set for fitting can influence the quantification 1,2, while other studies have shown the possible clinical relevance of macromolecules (MM) in clinical diagnostics 3. Hence, a characterization of MMs is of crucial importance 4, and knowing the apparent T2 (2$\varrho$) relaxation times can lead to a better understanding of these MMs.}
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Article Evaluating the impact of fast-fMRI on dynamic functional connectivity in an event-based paradigm Sahib, A., Erb, M., Marquetand, J., Martin, P., Klamer, S., Vulliemoz, S., Scheffler, K., Ethofer, T., Focke, N. {PLoS ONE}, 13(1):1-15, 2018
{The human brain is known to contain several functional networks that interact dynamically. Therefore, it is desirable to analyze the temporal features of these networks by dynamic functional connectivity (dFC). A sliding window approach was used in an event-related fMRI (visual stimulation using checkerboards) to assess the impact of repetition time (TR) and window size on the temporal features of BOLD dFC. In addition, we also examined the spatial distribution of dFC and tested the feasibility of this approach for the analysis of interictal epileptiforme discharges. 15 healthy controls (visual stimulation paradigm) and three patients with epilepsy (EEG-fMRI) were measured with EPI-fMRI. We calculated the functional connectivity degree (FCD) by determining the total number of connections of a given voxel above a predefined threshold based on Pearson correlation. FCD could capture hemodynamic changes relative to stimulus onset in controls. A significant effect of TR and window size was observed on FCD estimates. At a conventional TR of 2.6 s, FCD values were marginal compared to FCD values using sub-seconds TRs achievable with multiband (MB) fMRI. Concerning window sizes, a specific maximum of FCD values (inverted u-shape behavior) was found for each TR, indicating a limit to the possible gain in FCD for increasing window size. In patients, a dynamic FCD change was found relative to the onset of epileptiform EEG patterns, which was compatible with their clinical semiology. Our findings indicate that dynamic FCD transients are better detectable with sub-second TR than conventional TR. This approach was capable of capturing neuronal connectivity across various regions of the brain, indicating a potential to study the temporal characteristics of interictal epileptiform discharges and seizures in epilepsy patients or other brain diseases with brief events.}
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Miscellaneous Evolutionary Areal Expansion of the Human Anterior Insula Horn, F. 2018 BibTeX
Miscellaneous Ex vivo continuous Overhauser nuclear dynamic polarization in a SQUID-based ultralow field magnetic resonance imaging system Fehling, P., Bernard, R., Pohmann, R., Rudolph, M., Kölle, D., Kleiner, R., Scheffler, K., Buckenmaier, K. Joint Annual Meeting ISMRM-ESMRMB 2018, 2018
{Overhauser Dynamic Nuclear Polarization (ODNP) is a method to achieve continuous hyperpolarization in MR measurements. Here, the polarization of free radicals is transferred to 1H using High Frequency (HF) pulses at the electron Larmor frequency. At UltraLow Fields (ULF) the frequency of the HF pulse lies in the range of several 100 MHz and is able to penetrate large sample volumes, making continuous in vivo ODNP measurements possible. Since conventional Faraday coils are not sensitive enough at ULF, a Superconducting QUantum Interference Device (SQUID) based detector is employed. First ex vivo images using ODNP enhanced MR have been acquired successfully.}
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Miscellaneous Ex vivo continuous Overhauser nuclear dynamic polarization in a SQUID-based ultralow-field magnetic resonance imaging system Fehling, P., Bernard, R., Pohmann, R., Rudolph, M., Koelle, D., Kleiner, R., Scheffler, K., Buckenmaier, K. 82. Jahrestagung der Deutschen Physikalischen Gesellschaft und DPG-Frühjahrstagung, 96, 2018
{Overhauser Dynamic Nuclear Polarization (ODNP) is a hyperpolarization method for magnetic resonance measurements. The polarization of free radicals is transferred to 1H using HF pulses, thus enhancing the 1H signal. Only at UltraLow Fields (ULF) below 10 mT the corresponding HF pulse frequencies are low enough to penetrate large sample volumes, making continuous in vivo hyperpolarization possible. Since conventional Faraday coils are not sensitive enough at ULF, a SQUID-based detector is employed as the centerpiece of the ULF-MRI Scanner. With a superconducting second order gradiometric pickup coil the SQUID enables measurements with a sensitivity below 1 fT/$\surd$Hz. First proof-of-principle ex vivo images using ODNP enhanced, SQUID based ULF-MRI have been acquired successfully. This is an important step in the direction of a combined ULF MRI and magnetoencephalography system.}
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Miscellaneous Exploring the Origin of Asymmetries in the Balanced SSFP Profile at 9.4 Tesla: Microstructure Anisotropy or Chemical Exchange? Heule, R., Zaiss, M., Ehses, P., Scheffler, K. Joint Annual Meeting ISMRM-ESMRMB 2018, 2018
{The balanced steady-state free precession (bSSFP) profile is known to carry information about the tissue-dependent frequency content in a voxel. There has been strong evidence that the observed asymmetries in the bSSFP profile of white matter depend on the tract orientation with the largest asymmetries occurring in tracts perpendicular to B0. Recently, it was demonstrated that the bSSFP sequence can be used for chemical exchange detection based on profile asymmetries arising in isotropic probes of two exchanging pools. In this work, we explore the question whether exchanging species might contribute to the bSSFP profile asymmetry observed in white matter.}
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Miscellaneous Extra-retinal and intersensory aspects of cybersickness Hecht, H., Keshavarz, B., Nooij, S. TeaP 2018: Abstracts of the 60th Conference of Experimental Psychologists, 105, Pabst Science Publishers, Lengerich, Germany, 2018
{Visually induced motion sickness (VIMS) is a common side-effect in virtual environments and simulators. We hold that sea sickness and cyber sickness are of the same origin. In both cases, the vestibular afferents and proprioceptive information disagree with the visual information about body posture and movement. If one modality (or more) is in conflict with the physical movement of our body, motion sickness ensues. We report a number of studies that we have conducted to investigate how repeated exposure, complexity of the visual stimulus, odors, and music influence the genesis of VIMS. Since the standard method to measure VIMS, via the Simulator Sickness Questionnaire, is rather time-consuming, it does not lend itself to taking the repeated measures necessary to portray the time-course of VIMS. We have validated a fast motion sickness scale (FMS) that is up to the job. Our results qualify and refine the conflict theory of motion sickness \textendash and may even challenge it. On the one hand, basic visual parameters, such as brightness and contrast, were rather inconsequential for the degree of VIMS. On the other hand, vection, stereopsis, and other extra-retinal factors, such as music and odors, had substantial influence on the genesis of VIMS.}
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Miscellaneous Fast Track to the Neocortex: Long-term Memory Representations in the Parietal Cortex Brodt, S., Gais, S., Erb, M., Beck, J., Scheffler, K., Schönauer, M. 11th FENS Forum of Neuroscience, 2018
{Traditional models of systems memory consolidation postulate two interacting memory stores, with rapid encoding of new information supported by the hippocampus and a gradually developing, stable storage in neocortical circuits. Recently, the posterior parietal cortex (PPC), particularly the precuneus, has been proposed as a cardinal location of neocortical long-term memory. We have shown functional activity in this area over repeated learning that is memory specific, long-term stable and related to memory accuracy. To conclusively identify the PPC as a location of memory storage, learning-contingent, lasting structural changes have to be demonstrated as well. Here, we used diffusion MRI to assess changes in brain microstructure, which reflect neuronal plasticity. 41 participants learned object-place associations over 8 learning-recall repetitions in two sessions. Task-related activity was tracked with fMRI. Structural changes were assessed with dMRI at three time points (before, 90 minutes and 12 h after learning). A non-learning condition measured at the same times was employed as control. Functional PPC activity increases with learning repetitions, remains stable over a 13-h period and strongly correlates with recall performance. Furthermore, decreases in mean diffusivity indicate structural changes in the same area, which also develop after learning, remain stable for over 12 hours and correlate with behavioral performance. We thus show functional and structural changes in the PPC that fulfill all requirements for a neocortical long-term memory representation: learning specificity, long-term stability and behavioral relevance. The confirmation of structural plasticity in particular proves the importance of the PPC as a site of neocortical memory storage.}
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Article Fast track to the neocortex: A memory engram in the posterior parietal cortex Brodt, S., Gais, S., Beck, J., Erb, M., Scheffler, K., Schönauer, M. {Science}, 362(4618):1045-1048, American Association for the Advancement of Science, Washington, D.C., 2018
{Models of systems memory consolidation postulate a fast-learning hippocampal store and a slowly developing, stable neocortical store. Accordingly, early neocortical contributions to memory are deemed to reflect a hippocampus-driven online reinstatement of encoding activity. In contrast, we found that learning rapidly engenders an enduring memory engram in the human posterior parietal cortex. We assessed microstructural plasticity via diffusion-weighted magnetic resonance imaging as well as functional brain activity in an object-location learning task. We detected neocortical plasticity as early as 1 hour after learning and found that it was learning specific, enabled correct recall, and overlapped with memory-related functional activity. These microstructural changes persisted over 12 hours. Our results suggest that new traces can be rapidly encoded into the parietal cortex, challenging views of a slow-learning neocortex.}
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Miscellaneous Fat corrected APT-CEST in the human breast Zimmermann, F., Korzowski, A., Schuenke, P., Breitling, J., Zaiss, M., Paech, D., Ladd, M., Bachert, P., Goerke, S. 7th International Workshop on Chemical Exchange Saturation Transfer (CEST 2018), 73, 2018
{CEST in the mammary gland is affected by lipid signals1-5 not only causing strong pseudo rNOE artifacts4, but also leading to an incorrect normalization of the Z-spectrum in the spectral region of the amide proton transfer (APT) signal. Here, we propose to approximate the total fat signal by the residual magnetization at $\Delta$$\omega$ \textequals 0 ppm. This enables the correction of Z-spectra for fat signal induced artifacts without any additional measurements and thus fat independent quantitative APT-CEST imaging.}
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Article Fat label compared with fat content: gastrointestinal symptoms and brain activity in functional dyspepsia patients and healthy controls Lee, I., Kullmann, S., Scheffler, K., Preissl, H., Enck, P. {The American Journal of Clinical Nutrition}, 108(1):127-135, American Society for Nutrition, Bethesda, MD, USA, 2018
{Background High-fat meals are associated with dyspeptic symptoms in functional dyspepsia (FD) patients. It is still unclear how fat is processed, or how FD symptoms and neuronal activities are modulated by psychological factors. Objective We investigated brain activity by functional magnetic resonance imaging (fMRI) after the ingestion of high- and low-fat foods with correct/incorrect fat information. Design We compared 12 FD patients and 14 healthy controls (HCs). We recorded resting-state fMRI on four different days before and after ingestion of four yogurts (200 mL, 10\textpercent or 0.1\textpercent fat, \textquotedblleftlow fat\textquotedblright or \textquotedbllefthigh fat\textquotedblright label). Results FD patients showed more pronounced dyspeptic symptoms than did HCs, and symptoms were relieved less after consuming high fat\textendashlabeled yogurt than low fat\textendashlabeled yogurt, irrespective of the actual fat content. This is indicative of either a placebo effect of low-fat information or a nocebo effect of high-fat information on symptom expression. FD patients showed greater activity than did HCs in occipital areas before and after ingestion regardless of fat content and label, as well as greater activity in the middle frontal gyrus before ingestion. In addition, functional connectivity (FC) from the insula to the occipital cortex (I-O) increased after high fat ingestion and decreased after low fat ingestion in FD patients. FC from the insula to the precuneus (I-P) was higher in FD patients than in HCs after ingestion of low fat\textendashlabeled yogurt. In FD patients, I-O FC negatively correlated with nausea and I-P FC with FD symptom intensity, food craving, and depression. Conclusions Our results endorse the importance of psychological perception of food on the incidence of dyspeptic symptoms and on the altered brain activities. These findings show the importance of cognitive components in perceptions of fat, food craving, depression, and brain functions in pathophysiologic mechanisms of FD.}
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Miscellaneous Feature-based attention selectively modulates connectivity between sensory regions and attention and default networks Kwon, S., Bartels, A. 48th Annual Meeting of the Society for Neuroscience (Neuroscience 2018), 2018
{While numerous previous studies investigated how feature-based attention modulates mean neural activity, little is known about effects of feature-based attention on connectivity between feature-selective regions and nodes of the dorsal attention network or of the default mode network. Here we used a block design with ultra-long trials lasting 3 minutes that alternated between color attention, motion attention and passive viewing, involving the same stimuli. This paradigm allowed for high-quality functional connectivity measurements free of confounds related to on- and offset effects of stimulus blocks. Functional connectivity was measured between visual regions V4 and V5/MT+ (responsive to color and motion, respectively) with nodes of the dorsal attention network (DAN) and of the default mode network (DMN). Attention to color versus motion enhanced the connectivity between DAN and V4 more than between DAN and V5/MT, revealing selective enhancement of connectivity depending on the attended feature. Conversely, color versus motion attention reduced the connectivity between DMN and V4 more than between DMN and V5/MT+, showing feature-selective reduction in connectivity. The results hence show that not only nodes of the DAN selectively modulate connectivity with specific visual regions depending on the attended feature, but that the same holds true for nodes of the DMN, yet with inversed sign. The current study raises a role of DMN, previously known to be involved in rest, mind wandering or inversely in attention to external features, to interact with visual regions in a selective manner during feature selective attention.}
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Conference Paper Feel the Movement: Real Motion Influences Responses to Take-over Requests in Highly Automated Vehicles Borojeni, S., Boll, S., Heuten, W., Bülthoff, H., Chuang, L. In 2018 CHI Conference on Human Factors in Computing Systems, 1-13, ACM Press, Montreal, Canada, 2018
{Take-over requests (TORs) in highly automated vehicles are cues that prompt users to resume control. TORs however, are often evaluated in non-moving driving simulators. This ignores the role of motion, an important source of information for users who have their eyes off the road while engaged in non-driving related tasks. We ran a user study in a moving-base driving simulator to investigate the effect of motion on TOR responses. We found that with motion, user responses to TORs vary depending on the road context where TORs are issued. While previous work showed that participants are fast to respond to urgent cues, we show that this is true only when TORs are presented on straight roads. Urgent cues issued on curved roads elicit slower responses than non-urgent cues on curved roads. Our findings indicate that TORs should be designed to be aware of road context to accommodate natural user responses.}
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