1,721,072 research outputs found
Multimodal cortical neuronal cell type classification
No full textAbstract
Since more than a century, neuroscientists have distinguished excitatory (glutamatergic) neurons with long-distance projections from inhibitory (GABAergic) neurons with local projections and established layer-dependent schemes for the ~ 80% excitatory (principal) cells as well as the ~ 20% inhibitory neurons. Whereas, in the early days, mainly morphological criteria were used to define cell types, later supplemented by electrophysiological and neurochemical properties, nowadays. single-cell transcriptomics is the method of choice for cell type classification. Bringing recent insight together, we conclude that despite all established layer- and area-dependent differences, there is a set of reliably identifiable cortical cell types that were named (among others) intratelencephalic (IT), extratelencephalic (ET), and corticothalamic (CT) for the excitatory cells, which altogether comprise ~ 56 transcriptomic cell types (t-types). By the same means, inhibitory neurons were subdivided into parvalbumin (PV), somatostatin (SST), vasoactive intestinal polypeptide (VIP), and “other (i.e. Lamp5/Sncg)” subpopulations, which altogether comprise ~ 60 t-types. The coming years will show which t-types actually translate into “real” cell types that show a common set of multimodal features, including not only transcriptome but also physiology and morphology as well as connectivity and ultimately function. Only with the better knowledge of clear-cut cell types and experimental access to them, we will be able to reveal their specific functions, a task which turned out to be difficult in a part of the brain being so much specialized for cognition as the cerebral cortex
A special electrode holder for simultaneous intracellular patch recording and optical stimulation
No full text
A special electrode holder for simultaneous intracellular patch recording and optical stimulation
No full textThe Functioning of a Cortex without Layers
No full textA major hallmark of cortical organization is the existence of a variable number of layers, i.e., sheets of neurons stacked on top of each other, in which neurons have certain commonalities. However, even for the neocortex, variable numbers of layers have been described and it is just a convention to distinguish six layers from each other. Whether cortical layers are a structural epiphenomenon caused by developmental dynamics or represent a functionally important modularization of cortical computation is still unknown. Here we present our insights from the reeler mutant mouse, a model for a developmental, "molecular lesion"-induced loss of cortical layering that could serve as ground truth of what an intact layering adds to the cortex in terms of functionality. We could demonstrate that the reeler neocortex shows no inversion of cortical layers but rather a severe disorganization that in the primary somatosensory cortex leads to the complete loss of layers. Nevertheless, the somatosensory system is well organized. When exploring an enriched environment with specific sets of whiskers, activity-dependent gene expression takes place in the corresponding modules. Precise whisker stimuli lead to the functional activation of somatotopically organized barrel columns as visualized by intrinsic signal optical imaging. Similar results were obtained in the reeler visual system. When analyzing pathways that could be responsible for preservation of tactile perception, lemniscal thalamic projections were found to be largely intact, despite the smearing of target neurons across the cortical mantle. However, with optogenetic experiments we found evidence for a mild dispersion of thalamic synapse targeting on layer IV-spiny stellate cells, together with a general weakening in thalamocortical input strength. This weakening of thalamic inputs was compensated by intracortical mechanisms involving increased recurrent excitation and/or reduced feedforward inhibition. In conclusion, a layer loss so far only led to the detection of subtle defects in sensory processing by reeler mice. This argues in favor of a view in which cortical layers are not an essential component for basic perception and cognition. A view also supported by recent studies in birds, which can have remarkable cognitive capacities despite the lack of a neocortex with multiple cortical layers. In conclusion, we suggest that future studies directed toward understanding cortical functions should rather focus on circuits specified by functional cell type composition than mere laminar location
Persistence of Functional Sensory Maps in the Absence of Cortical Layers in the Somsatosensory Cortex of Reeler Mice
No full textIn rodents, layer IV of the primary somatosensory cortex contains the barrel field, where individual, large facial whiskers are represented as a dense cluster of cells. In the reeler mouse, a model of disturbed cortical development characterized by a loss of cortical lamination, the barrel field exists in a distorted manner. Little is known about the consequences of such a highly disturbed lamination on cortical function in this model. We used in vivo intrinsic signal optical imaging together with piezo-controlled whisker stimulation to explore sensory map organization and stimulus representation in the barrel field. We found that the loss of cortical layers in reeler mice had surprisingly little incidence on these properties. The overall topological order of whisker representations is highly preserved and the functional activation of individual whisker representations is similar in size and strength to wild-type controls. Because intrinsic imaging measures hemodynamic signals, we furthermore investigated the cortical blood vessel pattern of both genotypes, where we also did not detect major differences. In summary, the loss of the reelin protein results in a widespread disturbance of cortical development which compromises neither the establishment nor the function of an ordered, somatotopic map of the facial whiskers.Deutsche Forschungsgemeinschaft (DFG) via CRC [889
Neuromodulation Leads to a Burst-Tonic Switch in a Subset of VIP Neurons in Mouse Primary Somatosensory (Barrel) Cortex
No full textOptopatcher-An electrode holder for simultaneous intracellular patch-clamp recording and optical manipulation
No full textOptogenetics has rapidly become a standard method in neuroscience research. Although significant progress has been made in the development of molecular tools, refined techniques for combined light delivery and recording in vivo are still lacking. For example, simultaneous intracellular recording and light stimulation have only been possible by using two separate positioning systems. To overcome this limitation, we have developed a glass pipette holder which contains an additional port for the insertion of an optical fiber into the pipette. This device, which we called "optopatcher allows whole cell patch-clamp recording simultaneously with direct projection of light from the recording pipette. The holder spares the use of an additional manipulator and, importantly, enables accurate, stable and reproducible illumination. In addition, replacement of standard pipettes is done as easily as with the available commercial holders. Here we used the optopatcher in vivo to record the membrane potential of neurons from different cortical layers in the motor cortex of transgenic mice expressing channelrhodopsin-2 under the Thy1 promoter. We demonstrate the utility of the optopatcher by recording LFP and intracellular responses to light stimulation. (C) 2013 Elsevier B.V. All rights reserved
Functional thalamocortical innervation of VIP- and SST-expressing GABAergic interneurons in mouse barrel cortex
No full texthttp://dx.doi.org/10.13039/501100001659 German Research FoundationOpen-Access-Publikationsfonds 202
Direction selectivity of inhibitory interneurons in mouse barrel cortex differs between interneuron subtypes
No full texthttp://dx.doi.org/10.13039/501100001659 Deutsche Forschungsgemeinschaf
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