Glial cells help memory along

Study at the University of Bonn elucidates previously unknown mechanism for spatial learning

There are two fundamentally different cell types in the brain, neurons and glial cells. The latter, for example, insulate the “wiring” of nerve cells or guarantee optimal 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 type of glial cell plays an important role in spatial learning. The German Center for Neurodegenerative Diseases (DZNE) was involved in the work. The results have now been published in the journal Nature Communications.

Each place has numerous characteristics that distinguish it and make it unmistakable as a whole. A gnarled tree. A babbling brook at its foot. Fragrant wildflowers in the meadow behind. When we visit a place for the first time, we store this combination of features. When we then encounter the interplay of tree, brook, and wildflower meadow another time, our brain recognizes it: We remember having been there before.

This is made possible by mechanisms such as the so-called dendritic integration of synaptic activity. “We were able to show that the so-called astroglial cells or astrocytes play an essential role in this integration,” explains Prof. Dr. Christian Henneberger from the Institute of Cellular Neuroscience at the University Hospital Bonn. “They regulate how sensitive neurons are to a specific combination of features.”

In their study, the researchers took a close look at neurons in the hippocampus of rodents. The hippocampus is a region in the brain that plays a central role in memory processes. This is especially true for spatial memory: “In the hippocampus, there are neurons that specialize in just that – place cells,” says Henneberger, who is also a member of the Collaborative Research Center 1089 – where the research project was based – and the Transdisciplinary Research Area “Life & Health” at the University of Bonn. There are about one million of these place cells in the mouse hippocampus alone. Each responds to a specific combination of environmental characteristics.

Place 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 arrive at many neighboring synapses at the same time, a strong voltage pulse occurs in the dendrite – a so-called dendritic spike,” explains Dr. Kirsten Bohmbach, who performed most of the experiments in the study. “This process is what we call dendritic integration: The spike only occurs when a sufficient number of synapses are active at the same time. Such spikes travel toward the cell body, where they can trigger another voltage pulse – an action potential.” […]

Participating Core Facilities: The authors acknowledge the support from the Virus Core Facility.

Participating institutions and funding:
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 Study was funded by the German Research Foundation (DFG) and the returnee program of the state of North Rhine-Westphalia.

Publication: K. Bohmbach et al.: An astrocytic signaling loop for frequency-dependent control of dendritic integration and spatial learning; Nature Communications; DOI: 10.1038/s41467-022-35620-8

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