[mehr]

[mehr]

The search for the structures underlying human cognition, and their corresponding neural substrates, has preoccupied many psychologists and neuroscientists in recent decades. How should scientists best carve up the many dimensions of cognition, emotion, and action into distinct functions or faculties? Do the terms "working memory" and "executive control" reflect the same or different underlying processes? Are there such things as "basic" emotions, and if so, how many? Such questions are difficult to answer but important to ask. Unfortunately, none of them will be directly addressed in this talk. Instead, I will focus on a number of important methodological and conceptual issues surrounding our collective efforts to study the structure of the human mind via brain imaging methods. These include low sensitivity and specificity, poor construct validity, and a lack of isomorphism between constructs at different levels of description. Drawing on a series of recent studies, I demonstrate how large-scale meta-analyses of thousands of published fMRI studies can help us overcome many, but perhaps not all, of these issues. I conclude with a speculative discussion of the short-term and long-term prospects for a fully realized cognitive neuroscience of the human mind. [mehr]

[mehr]

Behavioral reports have traditionally been the gold standard for evaluating the presence of consciousness. However, it is becoming clear that consciousness can be present even in the absence of overt behavior and in unresponsive subjects. I will present neurophysiological evidence supporting the presence of consciousness in dissociated states from several domains. Measures of cortical integration and differentiation have recently proven to be the most reliable marker of consciousness irrespective of behavior and have been validated in a large number of different conditions. The most common dissociation between consciousness and behavior occurs every night during dreaming sleep. Recent work using both within-state, no-task paradigms and TMS-EEG shows that consciousness can be present during non REM sleep when the front of the brain shows high amplitude slow waves, as long as a posterior cortical hot zone is activated. Studies using different anesthetics have also shown that fully unresponsive subjects anesthetized with ketamine (as compared to propofol or xenon) retrospectively report intense dreams, which are again associated with high complexity responses to TMS, despite the occurrence of slow waves. High complexity responses can also be observed in about 20% of patients in a vegetative state suggesting, in line with previous findings using active paradigms, that a number of completely unresponsive patients may retain consciousness. Finally, a number of studies in healthy awake volunteers have emphasized frequent dissociations between consciousness and task-related cognitive functions. Overall, recent findings show that the anatomical neural correlates of consciousness are primarily localized to a posterior cortical hot zone that includes sensory areas, rather than to a fronto-parietal network involved in task monitoring and reporting. I will end by discussing promising avenues of future research. [mehr]

[mehr]

[mehr]

To better understand the normal and diseased human brain, reliable knowledge at the microstructural level is key. While ex-vivo histology remains the standard, advances in magnetic resonance imaging are making it increasingly possible to directly estimate histological markers and microstructural characteristics of brain tissue non-invasively. We have previously established methods for quantitative mapping of MR parameters at standard resolutions. However, to achieve the goal of integrating multi-modal MRI data into a unified model of MRI contrasts, cortical anatomy and tissue microstructure, unprecedented imaging resolutions will be required. As well as showing some of our latest 400 µm quantitative data, in this presentation I will outline our plans for developing in-vivo histology, and from an MR physics perspective highlight some of the technical challenges. Critical to achieving the necessary data quality are higher field strengths, RF coils, optical prospective motion correction and the retrospective correction of instrumental and physiological artefacts. While there is still much development to be done, data we are now acquiring holds promise for future studies of the microstructure and structure-function relationship of the living human brain. [mehr]

Registration: http://survey.cbs.mpg.de/index.php/437517/lang-en [mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

Embedded in an EU supported clinical trial (NISCI), we provide technical legwork concerning the setup of MRI sequences, quality assurence and data processing. The NISCI study concentrates on the treatment of spinalcord injury. Performing brain imaging within that context is supposed toserve as a new biomarker for de- and regeneration. The quantitative MRI technique of multi-parameter mapping will be the main draught horse. The application in clinical contexts requires some modifications. The most important differences to the research routine are (I) the use of vendor sequences instead of custom made ones and (II) the reduction of scanning time and resolution. To evaluate the protocol setup for consistency between and within sites (test-retest) we performed a traveling heads study with healthy subjects at four clinical sites. For processing the data we used the newly published hMRI-toolbox for quantitative MRI data (formerly VBQ-toolbox), which was further developed during the last year. In addition quality assurance scripts were designed to gain access to basic measures from specific brain regions within the processed quantitative maps. Also a promising solution for correcting susceptibility distortions from bipolar readout without the need of additional measurements (e.g. a fieldmap) will be presented. [mehr]

[mehr]

When we demonstrate children (or adults) a sequence of visibly causally irrelevant and relevant actions to reach a goal, they tend to imitate both, the irrelevant and the relevant actions - they 'overimitate'. Strikingly, apes don't do so. It is much debated what the underlying motivations for this human-specific apparently inefficient behavior could be. Do we overimitate because we draw erroneous causal conclusions from action observations or is it rather a strategy to affiliate with another person? Do we simply try to follow a social convention or a rule? In this talk we present a set of behavioral experiments, in which we contrasted explanatory models focusing on erroneous causal reasoning or social motivations; and present a new integrative explanatory model for overimitation. [mehr]

To optimally adapt to our ever-changing environments, our brain continuously integrates exteroceptive and interoceptive information, that is, signals received from external (e.g., through vision or touch) and internal sources (e.g., through viscerosensation or proprioception). Particularly the coupling between the heart and the brain or - more generally - between the autonomic and the central nervous system plays a major role for mental processes and behavior. I will present studies, in which we found (1) an association between resting heart rate variability (HRV) and resting-state functional connectivity, (2) task-related HRV changes in response to emotion or stress, and (3) that perception and behavior vary across the cardiac cycle. Showing the psychological relevance of both directions of the heart-brain axis suggests the "rest of the body’s" importance for the mind and contributes to a more comprehensive investigation of mind-brain-body interactions. [mehr]

[mehr]

[mehr]

The medial prefrontal cortex (mPFC) is part of a core network that not only supports the recollection of past episodes but also the imagining of prospective events (e.g., meeting a person at a particular place). Here, we use such episodic simulation and fMRI to provide insights into the exact functions supported by the mPFC. In the first part, RMWJB reports graph analytical evidence that the ventral mPFC acts as a hub that coordinates whole-brain connectivity. This region thus seems to support episodic simulation by effectively integrating distributed information (e.g., about the people and places featuring in an imagined event). In the second part, PCP uses representational-similarity analysis to examine the nature of the representations in the mPFC. Specifically, he tests the hypothesis that this region codes for affective associative representations of our environment. Together, the two parts will shed light on the functions supported by the mPFC by highlighting both, its internal representations and its influence on the brain’s overall functional connectivity. [mehr]

The arrangement, length, and microstructural properties of long-range connections in the central nervous system determine how information is distributed across the brain. To date, diffusion magnetic resonance imaging (dMRI)-based tractography is the only in vivo technique for mapping structural connections in the human brain. However, mapping from diffusion to fiber pathways is still ill-posed. As a result, tractography algorithms can take "wrong turns" and produce false positive and/or false negative connections. To address this problem, microstructure-informed tractography has been suggested. It is an emerging computational framework that associates each computed fiber tract with microstructural properties, e.g., metrics for axon diameter or density, using the dMRI technique. Our highly inter-disciplinary project with the above title is funded by the German Research Foundation (DFG) under the Priority Programme "Computational Connectomics" (SPP 2041). Four Principal Investigators (Siawoosh Mohammadi, Univ. Hamburg; Alfred Anwander & Stefan Geyer, MPI CBS Leipzig; Markus Morawski, Univ. Leipzig) plan to develop a computational framework for microstructure-informed tractography that addresses these limitations using multi-modal quantitative MRI at ultra-high spatial resolution. Moreover, we will develop an advanced ex vivo histology analysis strategy based on complementary 2-D (high-resolution semithin and ultrathin sectioning) and 3-D (CLARITY) techniques. We will combine histology with MRI ex vivo to validate the model at central junctions of long-range fiber pathways within the well characterized human voluntary motor control network. Our project aims at innovative new insights into MRI-based computational models for in vivo tractography. Funding started in May 2018. In this Institute Colloquium I will elaborate on the conceptual background from a neuroanatomical point of view and present first microstructural results. [mehr]

[mehr]

[mehr]

[mehr]

Compared to the spatial synchronization, temporal dynamics of neuronal activity only recently gained a widespread attention in neuroscience. A particularly interesting discovery was a demonstration of Long-Range Temporal Correlations (LRTC) in the amplitude dynamics of neuronal oscillations. Neuronal LRTC might indicate a presence of a critical state in neuronal dynamics which was previously shown to be beneficial for the optimal processing of information in the brain. In my talk I will review studies showing relevance of LRTC for cognitive and motor tasks. Moreover, I will show that LRTC can serve as clinical biomarkers sensitive to pathological neuronal activations in Schizophrenia, Depression and Parkinson’s Disease. [mehr]

[mehr]

[mehr]

[mehr]

[mehr]

Stroke is a leading cause of life-long disability. The improvement of acute treatment has increased stroke survival, leaving more people in rehabilitative care than ever. Here, the recovery of function typically reaches a plateau after initial progress. Transcranial direct current stimulation (tDCS) has been suggested to facilitate recovery beyond this plateau, even in the chronic stage. However, no clear pattern of tDCS-induced effects could be established in patients yet, likely due to inconsistent experimental designs in previous studies. In this talk I will present data from two studies I performed during my PhD here at the MPI CBS. The first (pilot) study covers differential effects of tDCS on proprioception in healthy ageing and introduces and applies an individualised current modelling approach to explain differences between age groups. In the second study, we have investigated a large array of sensorimotor functions in chronic stroke patients and the impact of two different tDCS protocols on the kinematics of those functions. [mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

The human medial temporal lobe (MTL) is essential for episodic memory, but the roles of its individual subregions remain a matter of debate. Anatomical and functional evidence suggests a division of labour based on stimulus domain: The MTL cortex may process domain-specific aspects of memory, with the anterior MTL cortex [perirhinal and anterolateral entorhinal cortices (PRC, alEC)] supporting object-related memory, and the posterior MTL cortex [parahippocampal and posteriormedial entorhinal cortices (PHC, pmEC)] supporting spatial memory. The hippocampus, on the other hand, may contribute to memory in a domain-general fashion. Here, I present data from three studies. Studies 1 and 2 investigated the domain-specificity of episodic memory using 3T fMRI. During incidental encoding (study 1) and associative recall (study 2), PRC and PHC contributed to object and scene memory, respectively. Study 3 utilised the ultra-high spatial resolution afforded by 7T fMRI to investigate the role of alEC, pmEC, and hippocampal subfields during associative encoding and retrieval of objects and scenes. Here, I will present preliminary results and highlight methodological challenges. In sum, these studies emphasise the role of the human MTL in episodic memory, with subregional differences that depend on stimulus domain. [mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

[mehr]

The OMEGA Lab’s research goal is to investigate lifestyle factors on brain health. In this colloquium, we will report on findings from the GUT-BRAIN study, a MPI in-house conducted double-blind cross-over within-subject designed randomized controlled trial. The study investigates potential effects of a two-week high-fiber diet in overweight healthy adults. We will report on a series of four projects, spanning from cross-sectional to longitudinal analyses. Associations of dietary and serum tyrosine on white matter microstructure and executive function Neurocognitive predictors of food memory Effects of a high-fiber diet on hypothalamic and peripheral inflammation Effects of a high-fiber diet on neural and behavioural correlates of food wanting Further studies on meal choices and methodological advances from the OMEGA Lab will be touched upon briefly. [mehr]

[mehr]

[mehr]

The spinal cord is not only the first part of the central nervous system where somatosensory information is processed, but also plays a substantial role in both acute and chronic forms of pain. While there is thus a clear incentive for investigating this structure in humans, assessing spinal cord function non-invasively comes with several unique obstacles. I will describe the approaches we have taken to address these challenges, focusing on fMRI data at 3T and 7T as well as electrophysiological work, which together aim to provide a spatiotemporal window into this underexplored part of the central nervous system. [mehr]

[mehr]

[mehr]

[mehr]

[mehr]

Magnetic fields are ubiquitous in nature and since a long time also in technology. Yet, there are many open questions, needs for research and emerging new applications. Standards need to be set or refined, and more accurate calibrations are required by industrial adopters of new technologies. A particular challenge and opportunity arise at the lowest end of the spectrum of magnetic fields. With demonstrated measurement sensitivities beyond the femtotesla (per root Hertz) scale, the neuronal activities of the brain following a peripheral nerve stimulus become detectable in a single trial, for example. While even the foundations of physics can be tested at the frontier of lowest metrological noise floors, a current trend is to make magnetic field measurement and imaging viable in application contexts beyond quantum physics laboratories. Here, we will discuss such developments in terms of sensor developments, measurement environments and key use cases. We will focus on atomic gas-based probes of stationary and slowly varying magnetic fields. With trapped ultracold gases, high resolution field mapping can be achieved with relevance to material developments such as indium tin oxide replacements for next-generation touch screens and solar panels. On the other hand, cells containing thermal atomic vapours can provide highest field sensitivities as part of optically pumped magnetometers with use in clinical neurology or current-density imaging in electric vehicle batteries. [mehr]