Publications by authors named "Martin K Schwarz"

Transplantation of induced pluripotent stem cell-derived neural cells represents a promising strategy for treating neurodegenerative diseases. However, reprogramming of somatic cells and their subsequent neural differentiation is complex and time-consuming, thereby impeding autologous applications. Recently, direct transcription factor-based conversion of blood cells into induced neural stem cells (iNSCs) has emerged as a potential alternative.

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To identify and extract naturalistic behavior, two methods have become popular: supervised and unsupervised. Each approach carries its own strengths and weaknesses (for example, user bias, training cost, complexity and action discovery), which the user must consider in their decision. Here, an active-learning platform, A-SOiD, blends these strengths, and in doing so, overcomes several of their inherent drawbacks.

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Common light sheet microscopy comes with a trade-off between light sheet width defining the optical sectioning and the usable field of view arising from the divergence of the illuminating Gaussian beam. To overcome this, low-diverging Airy beams have been introduced. Airy beams, however, exhibit side lobes degrading image contrast.

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Structural changes of astrocytes and their perisynaptic processes occur in response to various physiological and pathophysiological stimuli. They are thought to profoundly affect synaptic signalling and neuron-astrocyte communication. Understanding the causal relationship between astrocyte morphology changes and their functional consequences requires experimental tools to selectively manipulate astrocyte morphology.

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Organoids are stem cell-derived three-dimensional cultures offering a new avenue to model human development and disease. Brain organoids allow the study of various aspects of human brain development in the finest details in vitro in a tissue-like context. However, spatial relationships of subcellular structures, such as synaptic contacts between distant neurons, are hardly accessible by conventional light microscopy.

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Aggressive behavior is one of the most conserved social interactions in nature and serves as a crucial evolutionary trait. Serotonin (5-HT) plays a key role in the regulation of our emotions, such as anxiety and aggression, but which molecules and mechanisms in the serotonergic system are involved in violent behavior are still unknown. In this study, we show that deletion of the P/Q-type calcium channel selectively from serotonergic neurons in the dorsal raphe nuclei (DRN) augments aggressive behavior in male mice, while anxiety is not affected.

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In general, animal behavior can be described as the neuronal-driven sequence of reoccurring postures through time. Most of the available current technologies focus on offline pose estimation with high spatiotemporal resolution. However, to correlate behavior with neuronal activity it is often necessary to detect and react online to behavioral expressions.

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Stroke leads to the degeneration of short-range and long-range axonal connections emanating from peri-infarct tissue, but it also induces novel axonal projections. However, this regeneration is hampered by growth-inhibitory properties of peri-infarct tissue and fibrotic scarring. Here, we tested the effects of epothilone B and epothilone D, FDA-approved microtubule-stabilizing drugs that are powerful modulators of axonal growth and scar formation, on neuroplasticity and motor outcomes in a photothrombotic mouse model of cortical stroke.

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The controlled differentiation of pluripotent stem cells (PSCs) into neurons and glia offers a unique opportunity to study early stages of human central nervous system development under controlled conditions in vitro. With the advent of cell reprogramming and the possibility to generate induced pluripotent stem cells (iPSCs) from any individual in a scalable manner, these studies can be extended to a disease- and patient-specific level. Autism spectrum disorder (ASD) is considered a neurodevelopmental disorder, with substantial evidence pointing to early alterations in neurogenesis and network formation as key pathogenic drivers.

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Article Synopsis
  • Synaptic transmission in the hippocampus relies on astrocyte processes to clear the neurotransmitter glutamate, and the effectiveness of this process varies based on the coverage of individual synapses by astrocytes.
  • Smaller postsynaptic spines receive better protection from excess glutamate due to their stronger coverage by astroglial transporters compared to larger spines.
  • The study suggests that the size of the spine affects its sensitivity to glutamate levels and can influence synaptic communication, with smaller spines being more vulnerable to disruption from excess glutamate.
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Key Points: Thalamic activity is regulated by corticothalamic feedback from layers 5B and 6. To selectively study the importance of the layer 6 corticothalamic (L6 CT) projection, a transgenic mouse line was used in which layer 6 cells projecting to posterior medial thalamus (POm) were targeted for expression of channelrhodopsin-2. Repetitive optogenetic stimulation of this sub-type of L6 cells caused a rapid adaptation in POm spiking output, but had little effect on the spiking activity in the other cortical layers.

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Light-sheet fluorescence microscopy (LSFM) helps investigate small structures in developing cells and tissue for three-dimensional localization microscopy and large-field brain imaging in neuroscience. Lattice light-sheet microscopy is a recent development with great potential to improve axial resolution and usable field sizes, thus improving imaging speed. In contrast to the commonly employed Gaussian beams for light-sheet generation in conventional LSFM, in lattice light-sheet microscopy an array of low diverging Bessel beams with a suppressed side lobe structure is used.

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Resilience to stress is critical for the development of depression. Enhanced adenosine A receptor (AR) signaling mediates the antidepressant effects of acute sleep deprivation (SD). However, chronic SD causes long-lasting upregulation of brain AR and increases the risk of depression.

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The cerebellar involvement in cognitive functions such as attention, language, working memory, emotion, goal-directed behavior and spatial navigation is constantly growing. However, an exact connectivity map between the hippocampus and cerebellum in mice is still unknown. Here, we conducted a tracing study to identify the sequence of transsynaptic, cerebellar-hippocampal connections in the mouse brain using combinations of Recombinant adeno-associated virus (rAAV) and pseudotyped deletion-mutant rabies (RABV) viruses.

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Conventional antidepressants have limited efficacy and many side effects, highlighting the need for fast-acting and specific medications. Induction of the synaptic protein Homer1a mediates the effects of different antidepressant treatments, including the rapid action of ketamine and sleep deprivation (SD). We show here that mimicking Homer1a upregulation via intravenous injection of cell-membrane-permeable TAT-Homer1a elicits rapid antidepressant effects in various tests.

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An understanding of how the brain processes information requires knowledge of its underlying wiring diagrams, as well as insights into the relationship between circuit architecture and physiological function. Notably, rabies virus based single-cell genetic manipulations that can facilitate an experimental link between physiology and genetics have recently advanced the field of systems neuroscience. It allows capturing the synaptic and the anatomical receptive fields of individual neurons.

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Understanding the individual timeline of stem cell differentiation in vivo is critical for evaluating stem cell properties in animal models. However, with conventional ex vivo techniques, such as histology, the individual timeline of differentiation is not accessible. Therefore, we designed lentiviral plasmids with cell-specific promoters to control the expression of bioluminescence and fluorescence imaging reporters.

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The goal of understanding the architecture of neural circuits at the synapse level with a brain-wide perspective has powered the interest in high-speed and large field-of-view volumetric imaging at subcellular resolution. Here, we developed a method combining tissue expansion and light-sheet fluorescence microscopy to allow extended volumetric super resolution high-speed imaging of large mouse brain samples. We demonstrate the capabilities of this method by performing two color fast volumetric super resolution imaging of mouse CA1 and dentate gyrus molecular-, granule cell-, and polymorphic layers.

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A sudden aversive event produces escape behaviors, an innate response essential for survival in virtually all-animal species. Nuclei including the lateral habenula (LHb), the lateral hypothalamus (LH), and the midbrain are not only reciprocally connected, but also respond to negative events contributing to goal-directed behaviors. However, whether aversion encoding requires these neural circuits to ultimately prompt escape behaviors remains unclear.

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Dysfunctional astrocytes are increasingly recognized as key players in the development and progression of mesial temporal lobe epilepsy (MTLE). One of the dramatic changes astrocytes undergo in MTLE with hippocampal sclerosis (HS) is loss of gap junction coupling. To further elucidate molecular mechanism(s) underlying this alteration, we assessed expression, cellular localization and phosphorylation status of astrocytic gap junction proteins in human and experimental MTLE-HS.

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The concept of the tripartite synapse states that bi-directional signalling between perisynaptic astrocyte processes, presynaptic axonal boutons and postsynaptic neuronal structures defines the properties of synaptic information processing. Ca-dependent vesicular release from astrocytes, as one of the mechanisms of astrocyte-neuron communication, has attracted particular attention but has also been the subject of intense debate. In neurons, regulated vesicular release is a strongly coordinated process.

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Spike timing-dependent synaptic plasticity (STDP) serves as a key cellular correlate of associative learning, which is facilitated by elevated attentional and emotional states involving activation of adrenergic signaling. At cellular levels, adrenergic signaling increases dendrite excitability, but the underlying mechanisms remain elusive. Here we show that activation of β2-adrenoceptors promoted STD long-term synaptic potentiation at mouse hippocampal excitatory synapses by inactivating dendritic Kv1.

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While transplantation represents a key tool for assessing in vivo functionality of neural stem cells and their suitability for neural repair, little is known about the integration of grafted neurons into the host brain circuitry. Rabies virus-based retrograde tracing has developed into a powerful approach for visualizing synaptically connected neurons. Here, we combine this technique with light sheet fluorescence microscopy (LSFM) to visualize transplanted cells and connected host neurons in whole-mouse brain preparations.

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