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Axon to dendrite5/16/2023 Moreover, AcDs were rarely found in the upper layers of the neocortex: these layers are thicker in non-human primates and humans, and are associated with complex behaviors and higher cortical functions. This revealed that the proportion of pyramidal neurons with an AcD was around 10–20% in non-primate mammals (rat, cat and ferret), but much lower (typically a few percent) in macaque monkeys and humans. used a range of histological techniques to compare the morphology and structure of pyramidal neurons in postmortem tissue samples extracted from six cortical areas at different stages of the animals’ development ( Figure 2). Now, in eLife, Petra Wahle from Ruhr University Bochum and co-workers in Germany, Austria and Spain report that the proportion of axon carrying dendrites (AcDs) varies between mammalian species and different areas of the brain ( Wahle et al., 2022). Researchers are particularly interested in features that only occur in humans and primates, as these may be associated with cognitive behaviors as well as neurological and psychiatric conditions. These kinds of morphological differences are important because they influence how individual neurons and neuronal groups compute information. These ‘axon carrying dendrites’ are unusual because the signals dendrites receive are usually processed in the soma before they are sent out via the axon to other neurons ( Förster, 2014). Image credit: Adapted from Figure 1 in Wahle et al., 2022 Scale bars represent 100 micrometers for panel A, and 25 micrometers for the other panels. In some neurons, however, the axon emerges from a dendrite ( C), or initially co-joins with a dendrite as it exits from the soma ( D). Most pyramidal neurons contain an axon (indicated by the white arrow) that exits from the base of the soma ( B). Branching off the base of the soma are several basal dendrites, and a single apical dendrite protrudes from its apex. Dieser Mechanismus ermöglicht neue Wege der Informationsverarbeitung im Hippocampus und erweitert damit unser Verständnis über die biophysikalischen Vorgänge, denen Lernen und Gedächtnisbildung zugrunde liegen.( A) The neocortex of an infant macaque monkey that has been stained with dyes that label the dendrites and axons (initial segment only) of pyramidal neurons (shown in green). Mittels verschiedener neurowissenschaftlicher Techniken konnten wir nachweisen, dass axon-tragende Dendriten einen neuen und elektrisch begünstigten Typus von Signaleingängen darstellen, der sich in Stärke und Netzwerkverhalten von klassischen Dendriten hervorhebt. Diese Studie widmet sich der Charakterisierung dieses anatomischen Phänomens und untersucht dessen Einfluss auf die zelluläre Signalverarbeitung. Wir konnten jedoch bei einer großen Anzahl von hippocampalen Zellen den Axon-Ursprung am Dendritenbaum nachweisen. Beide Strukturen entspringen in der Regel direkt am Zellkörper. Baumartig verzweigte Dendriten empfangen Eingangssignale, während ein einzelnes Axon das Ausgangssignal erzeugt und an nachgeschaltete Zellen weiterleitet. Dortige Nervenzellen besitzen zwei spezialisierte Typen von Fortsätzen, welche eine gerichtete Informationsverarbeitung gewährleisten. Das Areal des Hippocampus gilt dabei als Schlüsselregion für den Transfer von neuen Erinnerungen ins Langzeitgedächtnis. This mechanism enables new ways to process information within the hippocampal structure and extends our knowledge about the biophysical foundations underlying memory formation.Įine der bedeutsamsten Leistungen unseres Gehirns besteht in der Fähigkeit, sich an vielfältige Ereignisse zu erinnern, Informationen zu verknüpfen und aus Vergangenem zu lernen. Using complementary techniques such as immunohistochemistry, electrophysiology and computer simulations we demonstrated that these axon-carrying dendrites constitute a privileged channel for excitatory synaptic input. This study focusses on the characterization of this particular anatomy and its influence on neuronal signal processing. However, we could show that in a large fraction of hippocampal neurons, the axon derives from one of the dendrites. Dendrites and axon arise usually directly from the somatic compartment. Their widely ramified dendrites receive input from other cells, whereas a single axon transmits output to subsequent cells of the network. Its neurons possess two specialized extensions to process information in a directed manner. The hippocampus, a part of the limbic system, is suspected to play a key role in the transformation of new experiences into long term memory. The ability to remember old events poses one of the most remarkable talents of the human brain. Neuroscience, axon, dendrite, AIS, axon-carrying dendrite, synaptic integration, hippocampus, CA1 pyramidal cell, Neurowissenschaften, Elektrophysiologie
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