Clusters of synaptic inputs on dendrites of layer 5 pyramidal cells in mouse visual cortex

The spatial organization of synaptic inputs on the dendritic tree of cortical neurons plays a major role for dendritic integration and neural computations, yet, remarkably little is known about it. We mapped the spatial organization of glutamatergic synapses between layer 5 pyramidal cells by combining optogenetics and 2-photon calcium imaging in mouse neocortical slices. To mathematically characterize the organization of inputs we developed an approach based on combinatorial analysis of the likelihoods of specific synapse arrangements. We found that the synapses of intralaminar inputs form clusters on the basal dendrites of layer 5 pyramidal cells. These clusters contain 4 to 14 synapses within <= 30 mu m of dendrite. According to the spatiotemporal characteristics of synaptic summation, these numbers suggest that there will be non-linear dendritic integration of synaptic inputs during synchronous activation

NMDA receptor subunit-dependent [Ca2+] signaling in individual hippocampal dendritic spines

Ca2+ influx through synaptic NMDA receptors (NMDA-Rs) triggers a variety of adaptive cellular processes. To probe NMDA-R-mediated [Ca2+] signaling, we used two-photon glutamate uncaging to stimulate NMDA-Rs on individual dendritic spines of CA1 pyramidal neurons in rat brain slices. We measured NMDA-R currents at the soma and NMDA-R-mediated [Ca2+] transients in stimulated spines (Delta[Ca2+]). Uncaging-evoked NMDA-R current amplitudes were independent of the size of the stimulated spine, implying that smaller spines contain higher densities of functional NMDA-Rs. The ratio of Delta[Ca2+] over NMDA-R current was highly variable (factor of 10) across spines, especially for small spines. These differences were not explained by heterogeneity in spine sizes or diffusional coupling between spines and their parent dendrites. In addition, we find that small spines have NMDA-R currents that are sensitive to NMDA-R NR2B subunit-specific antagonists. With block of NR2B-containing receptors, the range of Delta[Ca2+]/NMDA-R current ratios and their average value were much reduced. Our data suggest that individual spines can regulate the subunit composition of their NMDA-Rs and the effective fractional Ca2+ current through these receptors

Individual(l)tag : Single-day Novels zwischen Augenblicksästhetik und Alltagskritik

Besonderes Verdienst für die kulturwissenschaftliche Entdeckung des Alltags gebührt den Sozial- und Kulturkritikern Henri Lefebvre und Michel de Certeau, deren Schriften zum Verhältnis von Alltag und Gesellschaft in den 1960er bis 1980er Jahren maßgeblich zu einer Rehabilitation dieses bis dato gemeinhin mit der Vorstellung von Routine, habitualisierten Abläufen und Trivialität verbundenen Phänomens der modernen Lebenswelt beitrugen. Inzwischen gelten die Critiques de la vie quotidienne (1957-1981) sowie L’invention du quotidien (1980) zu den Gründungstexten der modernen Kulturwissenschaft und haben darüber hinaus maßgeblich zur Etablierung einer ganz und gar dem Phänomen Alltag gewidmeten Unterdisziplin, den Everyday Life Studies, beigetragen. Doch lange bevor der Alltag zu einem Objekt der wissenschaftlichen Neugier avancierte, war er bereits Gegenstand literarischer Darstellung. Davon zeugt der Roman des 18. Jahrhunderts ebenso wie der realistische Roman des 19. Jahrhunderts und die literarischen Produktionen des Naturalismus. Doch erst im Roman der Moderne gelangt der Alltag zu seinem vollen Recht, tritt er doch dort erstmals als spezifische Modalität der Erfahrung und des individuellen Bewusstseins in Erscheinung. Indem insbesondere das Subgenre des Single-day Novel Alltäglichkeit – so die zentrale These dieser Arbeit – als besondere Form von Wahrnehmung und Bewusstseinsaktivität fasst, also das Wahrnehmungsverhalten von Individuen in Alltagssituationen beobachtet und dabei immer wieder neu auszuhandelnde Ichentwürfe nachvollzieht, wird kulturwissenschaftliche Alltagsforschung avant la lettre betrieben. Dabei markiert der Tag als einziges sinnlich erfahrbares Zeitmaß die elementare temporale Kategorie der Alltagserfahrung, in der sich Triviales und Bedeutungsvolles begegnen. Als integraler Bestandteil solcher alltäglicher Bewusstseinsaktivität stellt sich die poetische Figuration des Augenblicks, wie sie etwa in den Epiphanien bei James Joyce oder den moments of being bei Virginia Woolf begegnet, heraus, die hier entgegen der literaturwissenschaftlichen Tendenz nicht als Gegenmodell zum Alltag sondern bereits seit den Vorläufermodellen aus dem 19. Jahrhundert maßgeblich als im Alltag befindlich beobachtet werden können. Dieser systematische Zusammenhang zwischen der Augenblicksästhetik der literarischen Moderne und ihrem lange übersehenen Interesse an Alltäglichkeit wird in dieser Arbeit entlang der Analyse der Single-day Novels Ulysses (James Joyce), Mrs Dalloway und Between the Acts (Virginia Woolf), Tauben im Gras (Wolfgang Koeppen), La Modifiaction (Michel Butor) sowie A Single Man (Christopher Isherwood) entwickelt.The social and cultural critics Henri Lefebvre and Michel de Certeau deserve particular credit for the discovery of everyday life in cultural studies. Their writings on the relationship between everyday life and society, dated in the 1960s to 1980s, made a significant contribution to the rehabilitation of this phenomenon of modern life, which until then had generally been associated with the idea of routine, habits and triviality. Critiques de la vie quotidienne (1957-1981) and L'invention du quotidien (1980) are now regarded as the founding texts of modern cultural studies and have also contributed significantly to the establishment of Everyday Life Studies, a sub-discipline dedicated entirely to the phenomenon of everyday life. But long before everyday life became an object of academic curiosity, it was already the subject of literary representation. The 18th century novel, the realistic novel of the 19th century and the literary productions of naturalism bear witness to this, but it is only in the modernist novel that everyday life comes into its own, appearing for the first time as a specific modality of experience and individual consciousness. The subgenre of the single-day novel, in particular, understands everydayness - according to the central thesis of this work - as a special form of perception and activity of consciousness, i.e. it observes the perceptual behaviour of individuals in everyday situations and, in doing so, by retracing the constantly renegotiated concepts of the self, cultural-scientific research into everyday life is being carried out avant la lettre. The day as the only sensually perceptible measure of time marks the elementary temporal category of everyday experience as the realm in which the trivial and the meaningful meet. The poetic figuration of the moment, as encountered in James Joyce's epiphanies or Virginia Woolf's moments of being, emerges as an integral part of such everyday activity of consciousness. Contrary to the tendency of literary studies so far, which used to take the moment as a counter-model to everyday life, it turns out as a significant part of everyday life, already since the predecessor models from the 19th century. This systematic connection between the momentary aesthetics of literary modernism and its long-overlooked interest in everydayness is explored by analysing the single-day novels Ulysses (James Joyce), Mrs Dalloway and Between the Acts (Virginia Woolf), Tauben im Gras (Wolfgang Koeppen), La Modifiaction (Michel Butor) and A Single Man (Christopher Isherwood)

Nonlinear [Ca2+] signaling in dendrites and spines caused by activity-dependent depression of Ca2+ extrusion

Spine Ca2+ triggers the induction of synaptic plasticity and other adaptive neuronal responses. The amplitude and time course of Ca2+ signals specify the activation of the signaling pathways that trigger different forms of plasticity such as long-term potentiation and depression. The shapes of Ca2+ signals are determined by the dynamics of Ca2+ sources, Ca2+ buffers, and Ca2+ extrusion mechanisms. Here we show in rat CA1 pyramidal neurons that plasma membrane Ca2+ pumps (PMCAs) and Na+/Ca2+ exchangers are the major Ca2+ extrusion pathways in spines and small dendrites. Surprisingly, we found that Ca2+ extrusion via PMCA and Na+/Ca2+ exchangers slows in an activity-dependent manner, mediated by intracellular Na+ and Ca2+ accumulations. This activity-dependent depression of Ca2+ extrusion is, in part, attributable to Ca2+-dependent inactivation of PMCAs. Ca2+ extrusion recovers from depression with a time constant of 0.5 s. Depression of Ca2+ extrusion provides a positive feedback loop, converting small differences in stimuli into large differences in Ca2+ concentration. Depression of Ca2+ extrusion produces Ca2+ concentration dynamics that depend on the history of neuronal activity and therefore likely modulates the induction of synaptic plasticity

Quantitative Analysis of the Spatial Organization of Synaptic Inputs on the Postsynaptic Dendrite

The spatial organization of synaptic inputs on the dendritic tree of cortical neurons is considered to play an important role in the dendritic integration of synaptic activity. Active electrical properties of dendrites and mechanisms of dendritic integration have been studied for a long time. New technological developments are now enabling the characterization of the spatial organization of synaptic inputs on dendrites. However, quantitative methods for the analysis of such data are lacking. In order to place cluster parameters into the framework of dendritic integration and synaptic summation, these parameters need to be assessed rigorously in a quantitative manner. Here I present an approach for the analysis of synaptic input clusters on the dendritic tree that is based on combinatorial analysis of the likelihoods to observe specific input arrangements. This approach is superior to the commonly applied analysis of nearest neighbor distances between synaptic inputs comparing their distribution to simulations with random reshuffling or bootstrapping. First, the new approach yields exact likelihood values rather than approximate numbers obtained from simulations. Second and more importantly, the new approach identifies individual clusters and thereby allows to quantify and characterize individual cluster properties

Multisensor für Bier-Qualität

In der heutigen Zeit ist es unumgänglich, die Qualität seiner Produkte darzulegen. Deshalb genügt es auch bei Getränken wie Bier nicht, das Bier zu probieren und eine vage Aussage zur Qualität zu machen. Es müssen genaue Parameter offengelegt und ausgewiesen werden, an welchen sich die Qualität des Bieres messen lasst. Des Weiteren wird zunehmend mit Bier betrogen, indem Etikettenschwindel betrieben wird. Da viele Messgerate für die Qualität von Bier teuer und nicht überall vorhanden sind, eignen sich diese Gerate nicht für den schnellen Einsatz. Ausserdem werden für verschiedene Parameter unterschiedliche einzelne Geräte benötigt, was ein zusätzliches Problem darstellt. Die Forschungsfrage in dieser Arbeit lautet daher: Ist es möglich ein preiswertes, optisches Wasser-Analysegerat so zu adaptieren, dass sich qualitätsrelevante Bierparameter messen und vergleichen lassen? Das Ziel ist, zu überprüfen ob sich ein preiswertes Wasser-Analyse Gerat zur Qualitätsmässig von Bier verwenden lasst. Des Weiteren soll überprüft werden, ob sich die Messung von Fluoreszenz bei Bier ebenfalls eignen konnte, um Aussagen über die Qualität zu treffen. Dies stellt eine bislang wenig erforschte Möglichkeit zur Bestimmung von Bierqualität dar. Die Methodik zur Erreichung der Ziele ist die Inbetriebnahme des Wasser-Analysegeräts und das Verstehen dessen Funktionsweise. Durch Recherchearbeit soll die Theorie zum Messprinzip und Normen zur Bierqualität aufgearbeitet werden. Anschliessend soll die Software auf der Grundlage der Theorie so adaptiert werden, dass sich qualitätsrelevante Bierparameter messen lassen. Mit einer ausführlichen Messreihe im Labor sollen die Messergebnisse verglichen und kalibriert werden können. Es zeigt sich, dass sich Farbe, Trübheit und Fluoreszenz mit dem Wasser-Analysegerat durch Adaption der Software messen lassen. Das adaptierte Analysegerat liefert nach ersten Kalibrierungen Messwerte, die gut mit den Referenzmesswerten aus dem Labor vergleichbar sind. Es zeigt sich ebenfalls, dass die Fluoreszenz bei Bier gut messbar ist. Jedoch stimmen die Ergebnisse mit dem Labor nicht gut mit den Messungen des adaptierten Analysegeräts überein. Dies konnte jedoch auf die Auswahl eines ungeeigneten Filters zurückzuführen sein. Es ist also durchaus sinnvoll, den Einsatz eines preiswerten optischen Analysegeräts für den schnellen und unkomplizierten Einsatz weiter zu prüfen. Zudem bietet die Messung der Fluoreszenz von Bier neue Möglichkeiten bei der Qualitätsmessung. Dafür muss ferner analysiert werden, welche Stoffe im Bier welchen Anteil Fluoreszenz aufweisen und wie sie in Relation zur Bierqualität stehen.In today’s world it is inevitable to state the quality of one’s products. Therefore, even with beverages such as beer, it is not enough to taste the beer and make a vague statement about its quality. Precise parameters must be disclosed and shown against which the quality of the beer can be measured. Furthermore, there is also increasing fraud with beer by labeling fraud. Since many measuring devices for the quality of beer are expensive and not available everywhere, these devices are not suitable for quick use. Furthermore, different individual instruments are needed for different parameters, which is an additional problem. The research question in this thesis is therefore: Is it possible to adapt an inexpensive optical water analyzer in such a way that quality-relevant beer parameters can be measured and compared? The objective is to verify whether a low-cost water analyzer can be used to measure the quality of beer. Furthermore, it is to be examined whether the measurement of fluorescence in beer could also be suitable for making statements about the quality. So far, this is a little researched possibility for the determination of beer quality. The methodology to achieve the objectives is to commission the water analyzer and understand how it works. Through research work, the theory on the measurement principle and standards on beer quality will be reviewed. Subsequently, the software is to be adapted on the basis of the theory in such a way that quality-relevant beer parameters can be measured. With an extensive series of measurements in the laboratory, the measurement results are to be compared and calibrated. It is shown that color, turbidity and fluorescence can be measured with the water analyzer by adapting the software. After initial calibrations, the adapted analyzer delivers measured values that compare well with the reference measured values from the laboratory. It also shows that the fluorescence in beer can be measured well. However, the results with the laboratory do not agree well with the measurements from the adapted analyzer. This could be due to the selection of an inappropriate filter. Thus, it is quite reasonable to further investigate the use of an inexpensive optical analyzer for quick and easy use. In addition, measuring the fluorescence of beer may offer new possibilities in quality measurement. For this purpose, it must also be analyzed which substances in the beer exhibit which proportion of fluorescence and how they relate to the beer quality

Characterization and subcellular targeting of GCaMP-type genetically-encoded calcium indicators

Genetically-encoded calcium indicators (GECIs) hold the promise of monitoring [Ca(2+)] in selected populations of neurons and in specific cellular compartments. Relating GECI fluorescence to neuronal activity requires quantitative characterization. We have characterized a promising new genetically-encoded calcium indicator-GCaMP2-in mammalian pyramidal neurons. Fluorescence changes in response to single action potentials (17+/-10% DeltaF/F [mean+/-SD]) could be detected in some, but not all, neurons. Trains of high-frequency action potentials yielded robust responses (302+/-50% for trains of 40 action potentials at 83 Hz). Responses were similar in acute brain slices from in utero electroporated mice, indicating that long-term expression did not interfere with GCaMP2 function. Membrane-targeted versions of GCaMP2 did not yield larger signals than their non-targeted counterparts. We further targeted GCaMP2 to dendritic spines to monitor Ca(2+) accumulations evoked by activation of synaptic NMDA receptors. We observed robust DeltaF/F responses (range: 37%-264%) to single spine uncaging stimuli that were correlated with NMDA receptor currents measured through a somatic patch pipette. One major drawback of GCaMP2 was its low baseline fluorescence. Our results show that GCaMP2 is improved from the previous versions of GCaMP and may be suited to detect bursts of high-frequency action potentials and synaptic currents in vivo

Inducing Different Neuronal Subtypes from Astrocytes in the Injured Mouse Cerebral Cortex

Astrocytes are particularly promising candidates for reprogramming into neurons, as they maintain some of the original patterning information from their radial glial ancestors. However, to which extent the position of astrocytes influences the fate of reprogrammed neurons remains unknown. To elucidate this, we performed stab wound injury covering an entire neocortical column, including the gray matter (GM) and white matter (WM), and targeted local reactive astrocytes via injecting FLEx switch (Cre-On) adeno-associated viral (AAV) vectors into mGFAP-Cre mice. Single proneural factors were not sufficient for adequate reprogramming, although their combination with the nuclear receptor-related 1 protein (Nurr1) improved reprogramming efficiency. Nurr1 and Neurogenin 2 (Ngn2) resulted in high-efficiency reprogramming of targeted astrocytes into neurons that develop lamina-specific hallmarks, including the appropriate long-distance axonal projections. Surprisingly, in the WM, we did not observe any reprogrammed neurons, thereby unveiling a crucial role of region- and layer-specific differences in astrocyte reprogramming

Live cell imaging reveals 3 '-UTR dependent mRNA sorting to synapses

mRNA transport restricts translation to specific subcellular locations, which is the basis for many cellular functions. However, the precise process of mRNA sorting to synapses in neurons remains elusive. Here we use Rgs4 mRNA to investigate 3'-UTR-dependent transport by MS2 live-cell imaging. The majority of observed RNA granules display 3'-UTR independent bidirectional transport in dendrites. Importantly, the Rgs4 3'-UTR causes an anterograde transport bias, which requires the Staufen2 protein. Moreover, the 3'-UTR mediates dynamic, sustained mRNA recruitment to synapses. Visualization at high temporal resolution enables us to show mRNA patrolling dendrites, allowing transient interaction with multiple synapses, in agreement with the sushi-belt model. Modulation of neuronal activity by either chemical silencing or local glutamate uncaging regulates both the 3'-UTR-dependent transport bias and synaptic recruitment. This dynamic and reversible mRNA recruitment to active synapses would allow translation and synaptic remodeling in a spatially and temporally adaptive manner