Publications

{MRCDI is a novel technique for non-invasive measurement of weak currents in the human head, which is important in several neuroscience applications. Here, we present reliable in-vivo MRCDI measurements in the human brain based on SSFP-FID, yielding an unprecedented accuracy. We demonstrate the destructive influences of stray magnetic fields caused by the current passing through feeding cables, and propose a correction method. Also, we show inter-individual differences in MRCDI measurements for two different current profiles, and compare the measurements with simulations based on individualized head models. The simulations of the current-induced magnetic fields show good agreement with in-vivo brain measurements.}

{Among the multitude of elements making up visual experience, color stands out in that it can specify both subjective experience and objective properties of the outside world. Whereas most neuroimaging research on human color vision has focused on external stimulation, the present study addressed this duality by investigating how externally elicited color vision is linked to subjective color experience induced by object imagery. We recorded fMRI activity while showing our participants abstract color stimuli that were either red, green, or yellow in half of the runs (\textquotedblleftreal-color runs\textquotedblright) and asked them to produce mental images of colored objects corresponding to the same three categories in the remaining half (\textquotedblleftimagery runs\textquotedblright). To make sure that participants were engaged in visual imagery, they performed a 1-back same/different color judgment task on the imagined objects. We trained color classifiers using MVPA to distinguish between fMRI responses to the three color stimuli and cross-validated them on data from real-color or imagery runs. Although real-color percepts could be predicted from all retinotopically mapped visual areas, only color decoders trained on hV4 responses could additionally predict the color category of an object that was being imagined. This suggests that sensory-driven and self-induced colors share a common neural code in hV4. Using a hierarchical drift diffusion model, we furthermore demonstrated that the decoding accuracy in hV4 was predictive of performance in the color judgment task on a trial-by-trial basis. The commonality between neural representations of perceived and imagined object color, in combination with the behavioral modeling evidence, hence identifies area hV4 as a \textquotedblleftperceptual bridge\textquotedblright linking externally triggered color vision with color in self-generated object imagery.}

{Color is special among basic visual features in that it can form a defining part of objects that are engrained in our memory. Whereas most neuroimaging research on human color vision has focused on responses related to external stimulation, the present study investigated how sensory-driven color vision is linked to subjective color perception induced by object imagery. We recorded fMRI activity in male and female volunteers during viewing of abstract color stimuli that were red, green, or yellow in half of the runs. In the other half we asked them to produce mental images of colored, meaningful objects (such as tomato, grapes, banana) corresponding to the same three color categories. Although physically presented color could be decoded from all retinotopically mapped visual areas, only hV4 allowed predicting colors of imagined objects when classifiers were trained on responses to physical colors. Importantly, only neural signal in hV4 was predictive of behavioral performance in the color judgment task on a trial-by-trial basis. The commonality between neural representations of sensory-driven and imagined object color and the behavioral link to neural representations in hV4 identifies area hV4 as a perceptual hub linking externally triggered color vision with color in self-generated object imagery.}

{A key question in vision research concerns how the brain compensates for self-induced eye and head movements to form the world-centered, spatiotopic representations we perceive. Although human V3A and V6 integrate eye movements with vision, it is unclear which areas integrate head motion signals with visual retinotopic representations, as fMRI typically prevents head movement executions. Here we examined whether human early visual cortex V3A and V6 integrate these signals. A previously introduced paradigm allowed participant head movement during trials, but stabilized the head during data acquisition utilizing the delay between blood-oxygen-level-dependent (BOLD) and neural signals. Visual stimuli simulated either a stable environment or one with arbitrary head-coupled visual motion. Importantly, both conditions were matched in retinal and head motion. Contrasts revealed differential responses in human V6. Given the lack of vestibular responses in primate V6, these results suggest multi-modal integration of visual with neck efference copy signals or proprioception in V6.}

{A key question in vision research concerns visual stability: how is visual information in retinal coordinates integrated with non-visual cues of self-induced motion to form the spatiotopic representations of the world that we perceive? Eye movements have been found to modulate retinotopic representations at multiple stages along the visual stream, yet a special role has been attributed to human areas V3A and V6, as both cancel self-induced retinal planar motion during eye movements to a near complete extent (Fischer, B\"ulthoff, Logothetis, Bartels, 2012). Beyond that, only little is known about which human visual processing stages integrate head motion signals with retinotopic representations as human fMRI is typically incompatible with execution of voluntary head movements. We recently circumvented these limitations and introduced a novel paradigm that allows participants to move their heads during fMRI scanning (Schindler and Bartels, 2018). The functional characteristics of the BOLD signal allowed us to temporally decouple stimulus presentation from the acquisition of stimulus evoked responses. Our custom-built air pressure based head-stabilization system permitted head-rotation during trials, but stabilized head position during data acquisition. Video-based head-tracking and head-mounted goggles allowed for real-time generation of visual stimuli taking head-motion into account. Observers viewed approaching visual flow through head-mounted MR-compatible goggles. A congruent condition simulated constant forward motion while the observer rotated the head relative to the body, as when looking around while being driven along a straight road. In the incongruent condition, observers performed identical head rotations, but the visual consequences were inversed such that visual and extra-retinal cues did not combine in any meaningful way. Crucially, both conditions were matched regarding head and retinal motion. Based on this paradigm, we previously examined the integration of head motion and visual signals in regions with established vestibular processing. Here we asked whether early visual cortex as well as areas V3A and V6 may integrate retinotopic visual representations with voluntary head motion. Contrasting congruent versus incongruent conditions revealed differential responses in human V6 but not in early visual regions or V3A, consistent with multi-modal integration of visual cues with head motion in human area V6. Our results extend previous evidence for multimodal integration in V6 to head-motion cues and are in line with the hypothesis of V6 as a crucial hub for compensation of self-induced motion.}

{Purpose Information on the electrical tissue conductivity might be useful for the diagnosis and characterization of pathologies such as tumors [1]. MRCDI and MREIT are two emerging non-invasive techniques for imaging of weak currents and ohmic conductivities. In this study, we demonstrated human in vivo brain MRCDI to pave the way for its clinical use [2], [3]. Methods In short, weak alternating currents up to 1\textendash2 mA are injected into human head in synchrony with tailored phase-sensitive MRI. The currents create a magnetic field , which shifts the precession frequency of the magnetization and modulates the acquired MR images. The acquired images are used to measure and reconstruct the current flow and conductivity distributions. We employed a steady-state free precession free-induction-decay (SSFP-FID) sequence in five subjects, and injected currents of 1 mA by an MR-conditional current source via electrodes attached to the scalp (two current profiles: Right-left (RL), electrodes placed near the temporoparietal junctions; anterior-posterior (AP), one attached to the forehead and one above the inion). Additionally, an ultra-short-echo-time sequence was performed to track the feeding cables for correcting the stray magnetic fields induced by cable currents. Corrected measurements were used to calculate current flow distributions and compared with Finite-Element simulations of the current flow based on individualized head models [4]. Results The current-induced magnetic field with was reliably measured and the reconstructed current flows showed good agreement with the simulations (average coefficient of determination R2\textequals 71\textpercent). The injected current flow differed substantially among individuals according to the electrode placements and anatomical differences. The calculated currents are stronger in CSF-filled highly conductive regions, e.g. the longitudinal fissure. Conclusions The strong correlation between the simulations and measurements validates the accuracy of the method and demonstrates the potential of the method for determining accurate brain tissue conductivities. These initial current flow recordings pave the way for human brain MREIT that might complement standard MR methods for tumor characterization.}

{Magnetic resonance current density imaging (MRCDI) and MR electrical impedance tomography (MREIT) are two emerging modalities, which combine weak time-varying currents injected via surface electrodes with magnetic resonance imaging (MRI) to acquire information about the current flow and ohmic conductivity distribution at high spatial resolution. The injected current flow creates a magnetic field in the head, and the component of the induced magnetic field $\Delta$Bz,c parallel to the main scanner field causes small shifts in the precession frequency of the magnetization. The measured MRI signal is modulated by these shifts, allowing to determine $\Delta$Bz,c for the reconstruction of the current flow and ohmic conductivity. Here, we demonstrate reliable $\Delta$Bz,c measurements in-vivo in the human brain based on multi-echo spin echo (MESE) and steady-state free precession free induction decay (SSFP-FID) sequences. In a series of experiments, we optimize their robustness for in-vivo measurements while maintaining a good sensitivity to the current-induced fields. We validate both methods by assessing the linearity of the measured $\Delta$Bz,c with respect to the current strength. For the more efficient SSFP-FID measurements, we demonstrate a strong influence of magnetic stray fields on the $\Delta$Bz,c images, caused by non-ideal paths of the electrode cables, and validate a correction method. Finally, we perform measurements with two different current injection profiles in five subjects. We demonstrate reliable recordings of $\Delta$Bz,c fields as weak as 1 nT, caused by currents of 1 mA strength. Comparison of the $\Delta$Bz,c measurements with simulated $\Delta$Bz,c images based on FEM calculations and individualized head models reveals significant linear correlations in all subjects, but only for the stray field-corrected data. As final step, we reconstruct current density distributions from the measured and simulated $\Delta$Bz,c data. Reconstructions from non-corrected $\Delta$Bz,c measurements systematically overestimate the current densities. Comparing the current densities reconstructed from corrected $\Delta$Bz,c measurements and from simulated $\Delta$Bz,c images reveals an average coefficient of determination R2 of 71\textpercent. In addition, it shows that the simulations underestimated the current strength on average by 24\textpercent. Our results open up the possibility of using MRI to systematically validate and optimize numerical field simulations that play an important role in several neuroscience applications, such as transcranial brain stimulation, and electro- and magnetoencephalography.}

{Studies of human and rodent navigation often reveal a remarkable cross-species similarity between the cognitive and neural mechanisms of navigation. Such cross-species resemblance often overshadows some critical differences between how humans and nonhuman animals navigate. In this review, I propose that a navigation system requires both a storage system (i.e., representing spatial information) and a positioning system (i.e., sensing spatial information) to operate. I then argue that the way humans represent spatial information is different from that inferred from the cellular activity observed during rodent navigation. Such difference spans the whole hierarchy of spatial representation, from representing the structure of an environment to the representation of sub-regions of an environment, routes and paths, and the distance and direction relative to a goal location. These cross-species inconsistencies suggest that what we learned from rodent navigation does not always transfer to human navigation. Finally, I argue for closing the loop for the dominant, unidirectional animal-to-human approach in navigation research, so that insights from behavioral studies of human navigation may also flow back to shed light on the cellular mechanisms of navigation for both humans and other mammals (i.e., a human-to-animal approach).}

{Despite its relevance for navigation surprisingly little is known about how goal direction bearings to distant locations are computed. Behavioural and neuroscientific models proposing the path integration of previously navigated routes are supported indirectly by neural data, but behavioral evidence is lacking. We show that humans integrate navigated routes post-hoc and incrementally while conducting goal direction estimates. Participants learned a multi-corridor layout by walking through a virtual environment. Throughout learning, participants repeatedly performed pairwise pointing from the start location, end location, and each turn location between segments. Pointing latency increased with the number of corridors to the target and decreased with pointing experience rather than environmental familiarity. Bimodal pointing distributions indicate that participants made systematic errors, for example, mixing up turns or forgetting segments. Modeling these error sources suggests that pointing did not rely on one unified, but rather multiple representations of the experimental environment. We conclude that participants performed incremental on-the-fly calculations of goal direction estimates within compartmentalised representations, which was quicker for nearby goals and became faster with repeated pointing. Within navigated environments humans do not compute difference vectors from coordinates of a globally consistent integrated \textquotedblleftmap in the head\textquotedblright.}

{Purpose Treatments using high-intensity focused ultrasound (HIFU) in the abdominal region remain challenging as a result of respiratory organ motion. A novel method is described here to achieve 3D motion-compensated ultrasound (US) MR-guided HIFU therapy using simultaneous ultrasound and MRI. Methods A truly hybrid US-MR-guided HIFU method was used to plan and control the treatment. Two-dimensional ultrasound was used in real time to enable tracking of the motion in the coronal plane, whereas an MR pencil-beam navigator was used to detect anterior\textendashposterior motion. Prospective motion compensation of proton resonance frequency shift (PRFS) thermometry and HIFU electronic beam steering were achieved. Results The 3D prospective motion-corrected PRFS temperature maps showed reduced intrascan ghosting artifacts, a high signal-to-noise ratio, and low geometric distortion. The k-space data yielded a consistent temperature-dependent PRFS effect, matching the gold standard thermometry within approximately 1\mbox{$^\circ$}C. The maximum in-plane temperature elevation ex vivo was improved by a factor of 2. Baseline thermometry acquired in volunteers indicated reduction of residual motion, together with an accuracy/precision of near-harmonic referenceless PRFS thermometry on the order of 0.5/1.0\mbox{$^\circ$}C. Conclusions Hybrid US-MR-guided HIFU ablation with 3D motion compensation was demonstrated ex vivo together with a stable referenceless PRFS thermometry baseline in healthy volunteer liver acquisitions.}

{Manual assembly at production is a mentally demanding task. With rapid prototyping and smaller production lot sizes, this results in frequent changes of assembly instructions that have to be memorized by workers. Assistive systems compensate this increase in mental workload by providing "just-in-time" assembly instructions through in-situ projections. The implementation of such systems and their benefits to reducing mental workload have previously been justified with self-perceived ratings. However, there is no evidence by objective measures if mental workload is reduced by in-situ assistance. In our work, we showcase electroencephalography (EEG) as a complementary evaluation tool to assess cognitive workload placed by two different assistive systems in an assembly task, namely paper instructions and in-situ projections. We identified the individual EEG bandwidth that varied with changes in working memory load. We show, that changes in the EEG bandwidth are found between paper instructions and in-situ projections, indicating that they reduce working memory compared to paper instructions. Our work contributes by demonstrating how design claims of cognitive demand can be validated. Moreover, it directly evaluates the use of assistive systems for delivering context-aware information. We analyze the characteristics of EEG as real-time assessment for cognitive workload to provide insights regarding the mental demand placed by assistive systems.}

{Introduction: Brain morphometry studies typically utilize anatomical data with 1 mm3 isotropic resolution. However, the widespread availability of high-field MRI scanners and receive coil arrays have led to increased interest in submillimeter resolution data. While higher resolution may have an advantage (Bazin et al., 2014; L\"usebrink et al., 2013; Zaretskaya et al., 2017), lifting this constraint on voxel size opens the door to a variety of acquisition protocols with a wide range of image contrast and SNR. Here we aim to systematically investigate the effects of image SNR on surface reconstruction quality based on sub-millimeter MPRAGE data acquired at 3T. Methods: To systematically vary image SNR without changing voxel size, we acquired multiple repetitions of high-resolution (0.6 mm isotropic) MPRAGE data from 9 participants, and for each subject generated multiple image volumes with progressively higher SNR by averaging together increasing number of repetitions (i.e. averaging 1 to 6 (n\textequals5) or 1 to 8 (n\textequals4) repetitions, depending on the total number of repetitions acquired within the session). Images were acquired on a 3T Siemens MAGNETOM Trio Tim system using a 32 channel coil and a 0.6 mm isotropic multiecho MPRAGE (van der Kouwe et al., 2008) protocol (TR/TE1/TE2/TI/FA/BW/ESP/matrix\textequals2510 ms/2.88 ms/ 5.6 ms/1200 ms/7\mbox{$^\circ$}/420 Hz/px/8.4 ms/400$\times$400). To minimize blurring during the inversion recovery, we used acceleration in the partition direction (R\textequals2) without partial Fourier in any direction and a slab-selective axial acquisition (slices per slab\textequals224) to minimize the number of partition encoding steps. Each average volume was used to generate cortical surfaces using FreeSurfer\textquotesingles native "hires" sub-millimeter reconstruction stream (Zaretskaya et al., 2017). To assess surface quality, for each set of surfaces (the gray-white and gray-CSF interface surfaces of each hemisphere) we computed the following parameters: (1) image SNR (the mean divided by the standard deviation of voxel intensities within the FreeSurfer white matter mask), (2) surface smoothness (defined as the median value of per-vertex local mean curvature), (3) number of topological defects in the initial surface, identified by FreeSurfer (Segonne et al., 2007), (4) median defect size. We also report gray-white matter contrast, derived from the reconstruction with 6 repetitions, and defined as the median of vertex-wise contrast values expressed as (white matter intensity \textendash gray matter intensity)/(white matter intensity + gray matter intensity)$\cdot$100. Results: Automatic reconstruction completed successfully in all but 2 cases. Both failed cases were comprised of a single repetition and could not complete automatically due to low SNR. The gray-white matter contrast of our data, based on averaging 6 repetitions for each subject, was 26.8 $\pm$ 0.4 (mean across subjects $\pm$ S.E.M). We observed a consistent increase in image SNR - accompanied by an increase in surface smoothness and by a decrease in the number of topological defects - with increasing number of repetitions included in the average. There was no change in the median defect size. While surface quality clearly improved with increasing SNR, gray-white surface smoothness and the number of defects did not reach a clear plateau even after 7 repetitions, suggesting that more repetitions may be needed to determine the SNR beyond which there is no noticeable improvement in surface quality. However, for this protocol and scanner, and across this small group of subjects, we find that qualitatively the performance of the surface reconstruction is adequate after averaging 5\textendash6 repetitions. Conclusions: Overall we show that averaging multiple repetitions can compensate for the corresponding loss of image SNR due to increase in image resolution. High-quality reconstructions can hence be generated from voxels far smaller than conventional acquisitions, even at standard field strength, provided sufficient data quality.}

{Reliable assessment and analysis of spontaneous mechanical activities in musculature (SMAM) visible in repetitive DWI is a relatively new technique for non-invasive characterization of skeletal musculature. To correct for data corrupted by intentional contractions, a surface electromyography-based contraction state analysis was investigated to reject undesired DWI data. It is demonstrated that the presented method enables a more reliable quantification of SMAMs and improved spontaneous activity maps.}

{Purpose To perform exchange-rate measurements on the in vivo human brain downfield spectrum (5\textendash10 ppm) at 9.4 T and to compare the variation in concentrations of the downfield resonances and of known upfield metabolites to determine potential peak labels. Methods Non-water-suppressed metabolite cycling was used in combination with an inversion transfer technique in two brain locations in healthy volunteers to measure the exchange rates and T1 values of exchanging peaks. Spectra were fitted with a heuristic model of a series of 13 or 14 Voigt lines, and a Bloch\textendashMcConnell model was used to fit the exchange rate curves. Concentrations from non-water-inverted spectra upfield and downfield were compared. Results Mean T1 values ranged from 0.40 to 0.77 s, and exchange rates from 0.74 to 13.8 s\textminus1. There were no significant correlations between downfield and upfield concentrations, except for N-acetylaspartate, with a correlation coefficient of 0.63 and P \textless 0.01. Conclusions Using ultrahigh field allowed improved separation of peaks in the 8.2 to 8.5 ppm amide proton region, and the exchange rates of multiple downfield resonances including the 5.8-ppm peak, previously tentatively assigned to urea, were measured in vivo in human brain. Downfield peaks consisted of overlapping components, and largely missing correlations between upfield and downfield resonances\textemdashalthough not conclusive\textemdashindicate limited contributions from metabolites present upfield to the downfield spectrum. Magn Reson Med, 2017. \copyright 2017 International Society for Magnetic Resonance in Medicine.}

{Purpose The transverse relaxation times T2 of 17 metabolites in vivo at 3T is reported and region specific differences are addressed. Methods An echo-time series protocol was applied to one, two, or three volumes of interest with different fraction of white and gray matter including a total number of 106 healthy volunteers and acquiring a total number of 128 spectra. The data were fitted with the 2D fitting tool ProFit2, which included individual line shape modeling for all metabolites and allowed the T2 calculation of 28 moieties of 17 metabolites. Results The T2 of 10 metabolites and their moieties have been reported for the first time. Region specific T2 differences in white and gray matter enriched tissue occur in 16 of 17 metabolites examined including single resonance lines and coupled spin systems. Conclusion The relaxation time T2 is regions specific and has to be considered when applying tissue composition correction for internal water referencing.}

{We investigated the possibility to observe the anatomical details of the superior colliculus (SC), a layered structure located on the tectum of the midbrain, by in vivo MRI at 9.4T. Through image analysis in native space, several brain structures of the mid brain could be identified. The signal variation of all imaging modalities (T1, R2\textasteriskcentered and QSM) along and across the superior colliculus consistently highlighted the deep white layer VII, adjacent to the periaqueductal grey; the myelinated fibres in the superficial optic layer (layer III) and an iron-rich layer attributed to the intermediate grey layer (IV).}

{Off-resonant spin-lock imaging enables a lot of possibilities for T1$\varrho$ and chemical exchange (CE) sensitive applications. For this purpose, a matching amplitude of the tipping and the locking pulse is required, which can be difficult due to the high power requirements of adiabatic pulses. In this work, we present a newly shaped adiabatic half-passage pulse, usable at low power to match the amplitude of the pulses. Off- and on-resonant saturated images acquired at 9.4T are shown. The new pulse shape is able to generate robust images with comparatively low power at ultra-high-field strengths.}

{Aims and objectives: Alzheimer\textquoterights Disease (AD) is the most common cause of dementia worldwide. So far univocal diagnosis of AD is only achieved by postmortem histology. Beta-Amyloid plaques are known to be classical hallmarks of the post mortem Alzheimer\textasciiacutes Disease brain. In-vivo, Beta-Amyloid deposits are currently detec[...] Methods and materials: Two patients with autosomal dominant AD (female 51y, male 35y) and two age and sex-matched healthy subjects (HS) were scanned at 9.4T using a multi-echo (N\textequals5) 3D-GRE sequence (0.375x0.375x0.8mm3 voxel size, TR\textequals35ms; TE\textequals6 to 30ms in steps of 6ms, TA\textequals9min, FOV\textequals192x174x70.4mm3, matrix size\textequals512x464x88) [...] Results: A variation of 70ms-1ca. in the effective transverse relaxation rate was observed between grey and white matter in AD patient compared to healthy subject (Figure 1). A pattern between grey and white matter, corresponding to paramagnetic effects, was also detected in the susceptibility map (0-0.04 pp[...] Conclusion: Both R2\textasteriskcentered and QSM methods at ultra-high field hold promise for detecting Beta-Amyloid load within the cortical rim providing a potential means for early diagnosis of AD in-vivo. Optimization of the QSM algorithm would likely increase the power of Beta-Amyloid detection ex-vivo and in-vivo.}

{We explored anatomical details of the superior colliculus (SC) by in vivo magnetic resonance imaging (MRI) at 9.4T. The high signal-to-noise ratio allowed the acquisition of high resolution, multi-modal images with voxel sizes ranging between 176 $\times$ 132 $\times$ 600 $\mu$m and (800)3$\mu$m. Quantitative mapping of the longitudinal relaxation rate R1, the effective transverse relaxation rate R2\textasteriskcentered, and the magnetic susceptibility QSM was performed in 14 healthy volunteers. The images were analyzed in native space as well as after normalization to a common brain space (MNI). The coefficient-of-variation (CoV) across subjects was evaluated in prominent regions of the midbrain, reaching the best reproducibility (CoV of 5) in the R2\textasteriskcentered maps of the SC in MNI space, while the CoV in the QSM maps remained high regardless of brain-space. To investigate whether more complex neurobiological architectural features could be detected, depth profiles through the SC layers towards the red nucleus (RN) were evaluated at different levels of the SC along the rostro-caudal axis. This analysis revealed alterations of the quantitative MRI parameters concordant with previous post mortem histology studies of the cyto- and myeloarchitecture of the SC. In general, the R1 maps were hyperintense in areas characterized by the presence of abundant myelinated fibers, and likely enabled detection of the deep white layer VII of the SC adjacent to the periaqueductal gray. While R1 maps failed to reveal finer details, possibly due to the relatively coarse spatial sampling used for this modality, these could be recovered in R2\textasteriskcentered maps and in QSM. In the central part of the SC along its rostro-caudal axis, increased R2\textasteriskcentered values and decreased susceptibility values were observed 2 mm below the SC surface, likely reflecting the myelinated fibers in the superficial optic layer (layer III). Towards the deeper layers, a second increase in R2\textasteriskcentered was paralleled by a paramagnetic shift in QSM suggesting the presence of an iron-rich layer about 3 mm below the surface of the SC, attributed to the intermediate gray layer (IV) composed of multipolar neurons. These results dovetail observations in histological specimens and animal studies and demonstrate that high-resolution multi-modal MRI at 9.4T can reveal several microstructural features of the SC in vivo.}

{Our phenomenological experience of the stable world is maintained by continuous integration of visual self-motion with extra-retinal signals. However, due to conventional constraints of fMRI acquisition in humans, neural responses to visuo-vestibular integration have only been studied using artificial stimuli, in the absence of voluntary head-motion. We here circumvented these limitations and let participants to move their heads during scanning. The slow dynamics of the BOLD signal allowed us to acquire neural signal related to head motion after the observer\textquotesingles head was stabilized by inflatable aircushions. Visual stimuli were presented on head-fixed display goggles and updated in real time as a function of head-motion that was tracked using an external camera. Two conditions simulated forward translation of the participant. During physical head rotation, the congruent condition simulated a stable world, whereas the incongruent condition added arbitrary lateral motion. Importantly, both conditions were precisely matched in visual properties and head-rotation. By comparing congruent with incongruent conditions we found evidence consistent with the multi-modal integration of visual cues with head motion into a coherent \textquotedblleftstable world\textquotedblright percept in the parietal operculum and in an anterior part of parieto-insular cortex (aPIC). In the visual motion network, human regions MST, a dorsal part of VIP, the cingulate sulcus visual area (CSv) and a region in precuneus (Pc) showed differential responses to the same contrast. The results demonstrate for the first time neural multimodal interactions between precisely matched congruent versus incongruent visual and non-visual cues during physical head-movement in the human brain. The methodological approach opens the path to a new class of fMRI studies with unprecedented temporal and spatial control over visuo-vestibular stimulation.}

{Deep generative models such as Generative Ad- versarial Networks (GANs) and Variational Auto- Encoders (VAEs) are important tools to capture and investigate the properties of complex empiri- cal data. However, the complexity of their inner elements makes their functioning challenging to interpret and modify. In this respect, these archi- tectures behave as black box models. In order to better understand the function of such network, we analyze the modularity of these system by quantifying the disentanglement of their intrinsic parameters. This concept relates to a notion of invariance to transformations of internal variables of the generative model, recently introduced in the field of causality. Our experiments on generation of human faces with VAEs supports that modu- larity between weights distributed over layers of generator architecture is achieved to some degree, and can be used to understand better the function- ing of these architectures. Finally, we show that modularity can be enhanced during optimization.}

{Introduction \& Aim: Mentally demanding tasks are often, but not always, those that place a high load on working memory. In fact, the N-back task is often relied on as the "ground truth" for evaluating brain-computer interfaces that seek to infer user experienced workload [Brouwer2011]. Manual production lines is a real-world example that requires workers to memorize complex assembly instructions, an aspect that is becoming more demanding in recent times as production lot sizes decrease. To assist manual assembly, in-situ displays have been developed that provide just-in-time instructions for assembly [Funk2016]. The utility of this in alleviating mental workload has been validated with measures such as questionnaires or semi-structured interviews, but never with neuroimaging. In this work, we employ electroencephalography (EEG) to evaluate the extent to which in-situ displays alleviate visuospatial working memory during manual assembly. Methods: An Emotiv Epoc was used to record EEG data throughout the whole experiment. In a within-subject study design (N\textequals12), participants were instructed to use either paper or projected in-situ instructions to assemble a Lego Duplo construction [Funk2016]. Paper instructions were printed on A4 sized sheets of paper. In-situ instructions were projected directly into the workplace (see Figure 1). Before the start of the assembly task, participants performed a one-minute eyes-opened/eyes-closed task followed by two N-back tasks (N\textequals0 and N\textequals2) to ensure a correct setup of the Emotiv Epoc through alpha desynchronization and to determine the individual bandwidth for alpha power. Afterward, participants started to assemble two different Lego Duplo starting with either paper or projected in-situ instructions based on the balanced Latin square. Ground truth for perceived workload is measured via NASA-TLX questionnaires filled out by participants after every N-back and assembly trial. Results: Alpha power was derived and noise suppressed by using a spatio-spectral decomposition filter [Nikulin2011]. Our findings show significantly higher alpha desynchronization when conducting an N-back task with N\textequals2 than N\textequals0, F(1, 11) \textequals 34.82, p \textless 0.001. By comparing projected in-situ and paper instructions, projected in-situ instructions showed significantly less alpha desynchronization than paper instructions, F(1, 11) \textequals 14.92, p \textless 0.003. This converges with collected NASA-TLX questionnaires evaluating perceived workload levels. We also found that item selection errors have significantly increased when using paper instructions instead of projected in-situ instructions, F(1, 11) \textequals 10.75, p \textless 0.007. Discussion and Conclusion: Our study shows encouraging results of using a low-cost EEG to evaluate assembly instruction system. Possible reasons for paper instructions causing higher alpha desynchronization, and thus working memory load, might be that every step (e.g. picking and placing a brick) has to be remembered by participants while projected in-situ instructions obviate the need for remembering single steps. This is backed up by a reduced number of item selection errors and supported by NASA-TLX questionnaires. This provides insights for developers to evaluate the feasibility of their assistive system design on a cognitive basis.}

{Touch is interpersonal, as it is shared between beings who have some mutual relation to one another, whether an intimate long-term relationship or a superficial one, and can be used to convey thoughts and feelings between conspecifics. We asked, participants to evaluate their own and someone else\textquoterights preference of \textquotedblleftwhich body part they prefer to touch\textquotedblright, during observed human social touch. Participants were shown pictures of an avatar, face-on, which had an upper body to either side of it, comprised of the neck, arm and palm. Avatars expressed preferences to one of the two bodies (left or right) and one of the three body parts (neck, arm and palm), indicated through combining positive/negative facial expressions, positive/negative gestures, and head orientation. Participants were asked to infer their own (1st-person mentalising) and the avatar\textquoterights (3rd-person mentalising) preference. Furthermore, driven by the notion that humans are highly susceptible to the happenings in their social environment, we introduced a third condition where the avatar showed no preference towards either body/body part (neutral condition), and asked participants to again evaluate their own preference. This allowed us to examine how social touch interactions may influence our subjective preferences. Overall, participants were faster in the neutral condition, than in the 1st-person mentalising and 3rd-person mentalising conditions. Although, participants\textquoteright preference was centred on the palm during the neutral condition, this was extended to include the arm and neck during 1st-person mentalising condition, suggesting that the avatar\textquoterights interaction with a specific body part influenced participants\textquoteright preference. In addition, participants were highly accurate in inferring the avatar\textquoterights \textquoteleftpreference\textquoteright, and showed that they were inclined to respond faster to positive facial expressions and gestures than negative, implying that they may share the touch recipient\textquoterights experience.}

{Information integration across the senses is fundamental for effective interactions with our environment. The extent to which signals from different senses can interact in the absence of awareness is controversial. Combining the spatial ventriloquist illusion and dynamic continuous flash suppression (dCFS), we investigated in a series of two experiments whether visual signals that observers do not consciously perceive can influence spatial perception of sounds. Importantly, dCFS obliterated visual awareness only on a fraction of trials allowing us to compare spatial ventriloquism for physically identical flashes that were judged as visible or invisible. Our results show a stronger ventriloquist effect for visible than invisible flashes. Critically, a robust ventriloquist effect emerged also for invisible flashes even when participants were at chance when locating the flash. Collectively, our findings demonstrate that signals that we are not aware of in one sensory modality can alter spatial perception of signals in another sensory modality.}

{Previous research on own body size estimation has only looked at estimates made by comparing own body size to a test body in front view (e.g., M\"olbert et al. 2017). However, people constantly see and compare themselves to bodies in different viewpoints. Depending on the viewpoint, shape cues potentially used to judge body size, such as the waist-to-hip ratio or the overall body outline, vary. Here, we asked whether viewpoint influences estimates of own body size in female participants. For each participant, a personalized female avatar was generated using weight, height, inseam, and arm span, and then variations of the personalized avatar having different weights ($\pm$5, $\pm$10, $\pm$15, $\pm$20, and $\pm$25) were created using a statistical body model. These eleven test bodies were presented in life-size in immersive virtual reality in six viewpoints: 0\mbox{$^\circ$}, $\pm$45\mbox{$^\circ$}, $\pm$90\mbox{$^\circ$}, 180\mbox{$^\circ$}. In a one-alternative forced choice paradigm, participants were asked to judge whether the test body was thinner or fatter than themselves. Results showed no significant influence of viewpoint on either the accuracy of body size estimation (PSE) or the sensitivity to weight changes (JND). Across all viewpoints, participants on average slightly overestimated their body weight (3.1) and could detect a weight difference of 5.2 in 50 of the trials. To further investigate whether females are also able to estimate own body size when the shape of the test bodies is clearly different to theirs, a set of personalized male avatars was generated for each participant and presented in front view using the same task. There was no difference in results between female and male test bodies. These results suggest that people are rather good at extracting body size independent of the viewpoint, and also from bodies with a very different shape.}

{In this work, we combined scanner\textquotesingles spherical harmonic shim coils with a local multi-coil shim array to work in parallel for dynamic shimming of the human brain at 9.4 T. Performance of the combined method is compared with global shimming with scanner\textquotesingles built-in shim setup, global shimming with multi-coil and dynamic shimming with multi-coil.}

{Background Ketamine is receiving increasing attention as a rapid-onset antidepressant in patients suffering from major depressive disorder (MDD) with treatment resistance or severe suicidal ideation. Ketamine modulates several neurotransmitter systems, including norepinephrine via the norepinephrine transporter (NET), both peripherally and centrally. The locus coeruleus (LC), which has high NET concentration, has been attributed to brain networks involved in depression. Thus we investigated the effects of single-dose of racemic ketamine on the LC using resting state functional MRI. Methods Fifty-nine healthy participants (mean age 25.57 $\pm$ 4.72) were examined in a double-blind, randomized, placebo-controlled study with 7 Tesla MRI. We investigated the resting state functional connectivity (rs-fc) of the LC before and one hour after subanesthetic ketamine injection (0.5 mg/kg), as well as associations between its rs-fc and a common polymorphism in the NET gene (rs28386840). Results A significant interaction of drug and time was revealed, and post hoc testing showed decreased rs-fc between LC and the thalamus after ketamine administration compared with baseline levels, including the mediodorsal, ventral anterior, ventral lateral, ventral posterolateral and centromedian nuclei. The rs-fc reduction was more pronounced in NET rs28386840 [AA] homozygous subjects than in [T] carriers. Conclusions We demonstrated acute rs-fc changes after ketamine administration in the central node of the norepinephrine pathway. These findings may contribute to understanding the antidepressant effect of ketamine at the system level, supporting modes of action on networks subserving aberrant arousal regulation in depression.}

{One of the principal goals in functional magnetic resonance imaging (fMRI) is the detection of local activation in the human brain. However, lack of statistical power and inflated false positive rates have recently been identified as major problems in this regard. Here, we propose a non-parametric and threshold-free framework called LISA to address this demand. It uses a non-linear filter for incorporating spatial context without sacrificing spatial precision. Multiple comparison correction is achieved by controlling the false discovery rate in the filtered maps. Compared to widely used other methods, it shows a boost in statistical power and allows to find small activation areas that have previously evaded detection. The spatial sensitivity of LISA makes it especially suitable for the analysis of high-resolution fMRI data acquired at ultrahigh field ($\geq$7 Tesla).}

{Long-TE gradient recalled-echo (GRE) scans are prone to phase artifacts due to B0 inhomogeneity. We propose a learning-based approach that does not rely on navigator readouts and allows to infer phase error offsets directly from corrupted data. Our method does not need to be pre-trained on a database of medical images that match a contrast/acquisition protocol of the input image. A sufficient input is a raw multi-coil spectrum of the image that needs to be corrected. We train a convolutional neural network to predict phase offsets for each k-space line of a 2D image. We synthesize training examples online by reconvolving the corrupted spectrum with point spread functions (PSFs) of the coil sensitivity profiles and superimposing artificial phase errors, which we attempt to predict. We evaluate our approach on \textquotedblleftin vivo\textquotedblright data acquired with GRE sequence, and demonstrate an improvement in image quality after phase error correction.}

{Neurodevelopmental disorders, such as ASD and ADHD, affect males about three to four times more often than females. 16p11.2 hemideletion is a copy number variation that is highly associated with neurodevelopmental disorders. Previous work from our lab has shown that a mouse model of 16p11.2 hemideletion (del/+) exhibits male-specific behavioral phenotypes. We, therefore, aimed to investigate with magnetic resonance imaging (MRI), whether del/+ animals also exhibited a sex-specific neuroanatomical endophenotype. Using the Allen Mouse Brain Atlas, we analyzed the expression patterns of the 27 genes within the 16p11.2 region to identify which gene expression patterns spatially overlapped with brain structural changes. MRI was performed ex vivo and the resulting images were analyzed using Voxel-based morphometry for T1-weighted sequences and tract-based spatial statistics for diffusion-weighted images. In a subsequent step, all available in situ hybridization (ISH) maps of the genes involved in the 16p11.2 hemideletion were aligned to Waxholm space and clusters obtained by sex-specific group comparisons were analyzed to determine which gene(s) showed the highest expression in these regions. We found pronounced sex-specific changes in male animals with increased fractional anisotropy in medial fiber tracts, especially in those proximate to the striatum. Moreover, we were able to identify gene expression patterns spatially overlapping with male-specific structural changes that were associated with neurite outgrowth and the MAPK pathway. Of note, previous molecular studies have found convergent changes that point to a sex-specific dysregulation of MAPK signaling. This convergent evidence supports the idea that ISH maps can be used to meaningfully analyze imaging data sets.}

{The invention relates to a liquid supply device for animals, especially for rodents, wherein a bottom of a liquid supply channel connecting a container and a tray is inclined by at least 1\mbox{$^\circ$} and by at most 5\mbox{$^\circ$} with respect to a reference plane.}

{Several well-established methods exist for recording and measuring the underlying signals of the brain; methods such as electrophysiology and fMRI, when taken together, have the capacity to disclose both local and global neuronal activity. Thus, we aimed to employ both techniques to construct a functional model of the insular cortex (IC), a recipient of afferents relaying information from the body\textquoterights viscera. For our work, we performed a series of fMRI experiments in the anesthetized macaque (n \textequals 11), where we measured the responses to interoceptive stimulation (e.g. lower gastrointestinal tract, cutaneous temperature, auricular vagus nerve branch, gustation); and exploited the gross functional anatomical localizations (area: 4mm2) of these functions to establish a foundation for subsequent electrophysiological sampling (area: 1mm2, n \textequals 4) across the IC. Using these methods, our results reveal a topographic organization of interoceptive processing and highlight its functional similarity to that of the human insular cortex. As localized by fMRI and electrophysiology, two anatomically discrete areas along the mid-anterior dorsal IC were responsive to oral and gustatory sensations. However, our fMRI results disclosed lower gastrointestinal activity to be predominantly correlated with the ventral anterior IC. Such results already depict a select arrangement of multi-modal inputs within the macaque insula. As the IC is the primary cortical recipient of interoceptive inputs, the manner in which this information is organized may disclose how these inputs are relayed to form a conscious percept of the body\textquoterights physiological state, contribute to emotional embodiment, and provide top-down influence on bodily function.}

{The Locus Coeruleus (LC) noradrenergic (NE) neuromodulatory system is critically involved in regulation of neural excitability via its diffuse ascending projections. Tonic NE release in the forebrain is essential for maintenance of vigilant states and increases the signal-to-noise ratio of cortical sensory responses. The impact of phasic NE release on cortical activity and sensory processing is less explored. We have previously reported that LC microstimulation caused a transient desynchronization of the population activity in the medial prefrontal cortex (mPFC), similar to noxious somatosensory stimuli. The LC receives nociceptive information from the medulla and therefore may mediate sensory signaling to its forebrain targets. Here, we performed extracellular recordings in LC and mPFC while presenting noxious stimuli in urethane-anesthetized rats. A brief train of foot shocks produced a robust phasic response in the LC and a transient change in the mPFC power spectrum with the strongest modulation in gamma (30-90 Hz) range. The LC phasic response preceded prefrontal gamma power increase and cortical modulation was proportional to the LC excitation. We also quantitatively characterized distinct cortical states and showed that sensory responses in both LC and mPFC depend on the ongoing cortical state. Finally, cessation of the LC firing by bilateral local iontophoretic injection of clonidine, $\alpha$2-adrenoreceotor agonist, completely eliminated sensory responses in the mPFC without shifting cortex to less excitable state. Together, our results suggest that the LC phasic response induces gamma power increase in the prefrontal cortex and is essential for mediating sensory information along ascending noxious pathway.}

{Measuring longitudinal relaxation times is a requirement for absolute quantification. In this work, to more accurately measure the concentrations of metabolites in vivo at 9.4T, the relaxation of 5 metabolites was measured using an inversion recovery MC-STEAM technique.}

{Looming sounds can be an ideal warning notification for emergency braking. This agrees with studies that have consistently demonstrated preferential brain processing for looming stimuli. This study investigates and demonstrates that looming sounds can similarly benefit emergency braking in managing a vehicle with adaptive cruise control (ACC). Specifically, looming auditory notifications induced the faster emergency braking times relative to a static auditory notification. Next, we compare the event-related potential (ERP) evoked by a looming notification, relative to its static equivalent. Looming notifications evoke a smaller fronto-central N2 amplitude than their static equivalents. Thus, we infer that looming sounds are consistent with the visual experience of an approaching collision and, hence, induced a corresponding performance benefit. Subjective ratings indicate no significant differences in the perceived workload across the notification conditions. Overall, this work suggests that auditory warnings should have congruent physical properties with the visual events that they warn for.}

{Braking responses are faster when drivers hear looming sounds that increase in intensity, relative to sounds with constant intensity (Gray, 2011). This finding agrees with research that has shown preferential neural processing for looming stimuli (e.g., Tyll et al., 2013). It remains unknown if the looming benefit reported by Gray (2011) was due to the perceived saliency of looming sounds, or as a result of their ability to re-direct attention away from vehicle control to braking. The current study was conducted in a driving simulation for a vehicle with automated lateral and longitudinal control. Participants were only required to perform emergency braking if the lead vehicle suddenly braked. We found fastest braking times when these instances were accompanied by a looming sound (M\textequals825 ms), relative to a constant sound (M\textequals844 ms), or no sound (M\textequals1098 ms; F(1.29, 23.3)\textequals200, p\textless.05, ?2\textequals0.9). There was no significant difference in false brakings induced by looming and constant sounds (t(18)\textequals.57, p\textequals.58). Thus, we find that looming sounds facilitate braking without increasing a bias for braking. This work demonstrates that looming sounds can hasten braking directly, even in the absence of task-switching. We discuss the implications of this work to auditory warning design.}

{A snapCEST sequence was optimized for imaging of protein CEST effects at 3T with low saturation power. Full Z-spectrum sampling allows Lorentzian fitting of amide, NOE, semisolid MT, and water pools. Validation against data acquired at 9.4T demonstrates effective labeling of selective amide and NOE CEST effects at 3T. Data acquired in a brain tumor patients demonstrates clinical feasibility.}

{MRI of post mortem samples in formalin is an essential tool for validation purposes and comparison with clinical histology, since fixation preserve several microstructural tissue features. We found that the dielectric properties of the fixative influences image quality attained in whole brain post mortem samples at 9.4T. The standard fixative prevented high quality MRI across the entire sample. By using a high conductivity fixative with less field focussing, a more homogeneous excitation was achieved without any drop outs and T1 mapping could be performed using rapid inversion recovery techniques.}

{Spinal cord injury (SCI) is a very heterogeneous disease that makes it difficult to identify a single biomarker during rehabilitation therapy in order to predict the future patient status. In this study, we applied Magnetic Resonance Spectroscopy to examine specific metabolic markers in the pons 10 weeks after injury and correlated them with changes of the clinical status obtained twice during early rehabilitation.}