When the mouse is spatially oriented and then increase the likelihood of dendritic spikes by signaling molecules, astrocytes (yellow) find. Credit: Dr. Kirsten Bohmbach/University Hospital Bonn
Study at the University of Bonn illuminates previously unidentified mechanism for spatial learning.
There are two basically various cell key ins the brain, nerve cells, and glial cells. One function of the latter is to insulate the “circuitry” of nerve cells or guarantee optimum working conditions for them. A new study led by the University of Bonn has now discovered another function in rodents: The results suggest that a certain kind of glial cell plays an essential role in spatial knowing. The German Center for Neurodegenerative Diseases (DZNE) was involved in the work. The outcomes have actually now been published in the journal Nature Communications.
Each place has various characteristics that distinguish it and make it unmistakable as a whole. When we check out a location for the first time, we save this combination of functions. When we then experience the interplay of tree, brook, and wildflower meadow another time, our brain acknowledges it: We remember having been there in the past.
This is enabled by mechanisms such as the so-called dendritic combination of synaptic activity. “We had the ability to show that the so-called astroglial cells or astrocytes play a necessary role in this integration,” describes Prof. Dr. Christian Henneberger from the Institute of Cellular Neuroscience at the University Hospital Bonn. “They control how sensitive neurons are to a specific combination of functions.”
One million location cells in the mouse brain
In their study, the scientists took a close look at nerve cells in the hippocampus of rodents. There are about one million of these place cells in the mouse hippocampus alone.
Location cells have long extensions, the dendrites. These are branched like the crown of a tree and dotted with numerous contact points. Information that our senses convey to us about a location arrives here. These contacts are called synapses. “When signals come to numerous neighboring synapses at the very same time, a strong voltage pulse takes place in the dendrite– a so-called dendritic spike,” explains Dr. Kirsten Bohmbach, who carried out most of the experiments in the research study. “This process is what we call dendritic integration: The spike just occurs when an adequate variety of synapses are active at the exact same time. Such spikes travel towards the cell body, where they can set off another voltage pulse– an action potential.”
Place cells in attention mode
Place cells create action capacities at regular periods. The speed at which they do this can differ extensively. Nevertheless, when mice orient themselves in a new environment, their location cells constantly oscillate in an unique rhythm– they then create 5 to 10 voltage pulses per second. This rhythm causes the nerve cells to launch particular messenger compounds. And this is where astrocytes come in: They have sensing units to which these messenger compounds dock, and in turn, release a substance called D-serine.
” The D-serine then moves to the dendrites of the place cells,” Bohmbach discusses. “There, it ensures that the dendritic spikes can establish more easily and are also much more powerful.” This makes it easier for them to store and recognize new areas when mice are in orientation mode. It resembles a taxi driver focusing on browsing through the city center and remembering altering areas. The traveler next to the chauffeur is also taking a look at the roadway, but his ideas are elsewhere and he notifications less (nevertheless, there are likewise quite different procedures included in such attention phenomena).
” If we hinder the assistance provided by astrocytes in mice, they are less likely to acknowledge familiar places,” Henneberger says. However, this does not use to locations that are particularly relevant– for example, because they pose a potential risk: These continue to be prevented by the animals. “The system we discovered therefore manages the threshold at which location info is stored or acknowledged.” The results supply a new insight into how memory is and works managed. In the medium term, they may also help to address the question of how specific forms of memory disorders develop.
The research study outcomes are also an expression of fruitful intra-university cooperation: “They would not have been possible without the intensive collaboration with Prof. Dr. Heinz Becks lab at the Institute of Experimental Epileptology and Cognitive Sciences and, in specific, his coworkers Dr. Nicola Masala and Dr. Thoralf Opitz,” Henneberger highlights.
Recommendation: “An astrocytic signaling loop for frequency-dependent control of dendritic integration and spatial learning” by Kirsten Bohmbach, Nicola Masala, Eva M. Schönhense, Katharina Hill, André N. Haubrich, Andreas Zimmer, Thoralf Opitz, Heinz Beck and Christian Henneberger, 24 December 2022, Nature Communications.DOI: 10.1038/ s41467-022-35620-8.
In addition to the University of Bonn and the University Hospital Bonn, the German Center for Neurodegenerative Diseases (DZNE) and University College London were involved in the work. The research study was funded by the German Research Foundation (DFG) and the returnee program of the state of North Rhine-Westphalia.
There are two fundamentally various cell types in the brain, nerve cells, and glial cells. There are about one million of these location cells in the mouse hippocampus alone. Location cells create action potentials at regular intervals. When mice orient themselves in a brand-new environment, their place cells always oscillate in a special rhythm– they then create 5 to ten voltage pulses per second.” The D-serine then moves to the dendrites of the place cells,” Bohmbach describes.
