Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Deep inside the brain: Unraveling the dense networks in the cerebral cortex

25.10.2019

Mammalian brains, with their unmatched number of nerve cells and density of communication, are the most complex networks known. While methods to analyze neuronal networks sparsely have been available for decades, the dense mapping of neuronal circuits is a major scientific challenge. Researchers from the MPI for Brain Research have now succeeded in the dense connectomic mapping of brain tissue from the cerebral cortex, and quantify the possible imprint of learning in the circuit.

Unlike any other organ, our brains contain extremely densely packed networks of membranous cables that are used by our about 86 billion nerve cells for communication amongst each other. Since each nerve cell in the main part of mammalian brains, the so-called cerebral cortex, communicates with about 1,000 other nerve cells via synapses placed along these cables over long distances, one expects a total of about 5 million kilometers of wires packed into our skulls – more than 10 times longer than all highways on our planet, in each of our brains.


Small fraction of dendrites (gray) and synapses (orange) in a piece of mouse cortex, reconstructed from 3D electron microscopy data.

J Kuhl (somedonkey.com), Motta, Wissler (c) MPI for Brain Research


Dense connectome from the mouse cerebral cortex, the largest connectome to date.

Reprinted with permission from A Motta et al., Science. DOI: 10.1126/science.aay3134

The cables we find in our (and other mammalian) brains are as thin as 50 to 100 nanometers in diameter, about 1000th the diameter of our hairs. The resulting cable convolute is of such density and magnitude, that for more than 100 years, researchers have been able to only map connectivity between a miniscule fraction of neurons in a given piece of brain.

Only the development of faster electron microscopic techniques (“3D EM”) and of more efficient image analysis routines has made the dense mapping of neuronal networks possible. The novel field of “connectomics” has been pursuing the dense mapping of ever larger circuits in several species and brain regions.

In the work published today in Science, a team around Max Planck Director Moritz Helmstaedter imaged and analyzed a piece of tissue from the cerebral cortex of a 4-week old mouse, obtained via biopsy from the somatosensory cortex, a part of the cortex occupied with the representation and processing of touch.

Here, the researchers applied optimized AI-based image processing and efficient human-machine interaction to analyze all of the about 400,000 synapses and about 2.7 meters of neuronal cable in the volume. With this, they produced a connectome between about 7,000 axons and about 3,700 postsynaptic neurites, yielding a connectome about 26 times larger than the one obtained from the mouse retina more than half a decade ago.

Importantly, this reconstruction was at the same time larger and about 33-times more efficient than the one applied to the retina, setting a new benchmark for dense connectomic reconstruction in the mammalian brain.

Fueled by this this methodological breakthrough in connectomics, the researchers analyzed the connectome for the patterns of circuitry present. In particular, they asked what fraction of the circuit showed properties that were consistent with the growth of synapses, mechanisms known to contribute to circuit formation and “learning”.

Alessandro Motta, first author of the study and an electrical engineer by training, used particular configurations of synapse pairs to study the degree to which they were in agreement with activity-related learning processes (“LTP”). “Because some models of synaptic plasticity make concrete predictions about the increase in synaptic weight when learning, say, to identify a tree or a cat, we were able to extract the imprint of such potential processes even from a static snapshot of the circuit”, explains Motta.

Since the mouse had had a normal laboratory life until the brain biopsy at 4 weeks of age, the scientists argue that the degree to which circuits are shaped by learning in “normal” sensory states can be mapped using their approach.

“We were surprised how much information and precision is found even in a still relatively small piece of cortex”, says Helmstaedter, and adds “Especially the extraction of the likely learned circuit fraction was a major eye opener for us”.

The reported methods may have substantial implications for the transfer of insights about biological intelligence to what today is called “artificial intelligence”. “The goal of mapping neuronal networks in the cerebral cortex is a major scientific adventure, also because we hope to be able to extract information about how the brain is such an efficient computer, unlike today’s AI”, states Helmstaedter.

And describes a research field with major players including Google and the research program of the intelligence agencies in the US (IARPA): “The ambition to learn from biological neuronal networks about the future of artificial neuronal networks is shared by major initiatives world-wide. We are very proud about having achieved the first milestone, a dense local cortical connectome, using exclusively public funding from the Max Planck Society”.

After almost a decade of work, the researchers are enthusiastic about their achievements. “Being able to take a piece of cortex, process it diligently, and then obtain the entire communication map from that beautiful network is what we have been working for over the last decade”, describes Helmstaedter.

The researchers conclude: “We think that our methods, applied over a large range of cortical tissues from different brain areas, cortical layers, developmental time points, and species will tell us how evolution has designed these networks, and what impact experience has on shaping their fine-grained structure”.

“Moreover, connectomic screening will allow the description of circuit phenotypes of psychiatric and related disorders – and tell us to what degree some important brain disorders are in fact connectopathies, circuit diseases.”

Wissenschaftliche Ansprechpartner:

Dr. Moritz Helmstaedter
Email: mh@brain.mpg.de
Phone: 0049 (0) 69 850033 3001

Originalpublikation:

Motta, Berning, Boergens, Staffler, Beining, Loomba, Hennig, Wissler, Helmstaedter. Dense connectomic reconstruction in layer 4 of the somatosensory cortex.
Science. October 24, 2019. DOI:http://science.sciencemag.org/lookup/doi/10.1126/science.aay3134.

Weitere Informationen:

https://youtu.be/bpIKBkf5QRE Analysis of neurons and their synapses in a dense reconstruction from the cerebral cortex. Credits: Wissler, Motta, Helmstaedter (c) MPI for Brain Research

Dr. Irina Epstein | Max-Planck-Institut für Hirnforschung
Further information:
http://www.brain.mpg.de/

More articles from Life Sciences:

nachricht Turning carbon dioxide into liquid fuel
06.08.2020 | DOE/Argonne National Laboratory

nachricht Tellurium makes the difference
06.08.2020 | Friedrich-Schiller-Universität Jena

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: ScanCut project completed: laser cutting enables more intricate plug connector designs

Scientists at the Fraunhofer Institute for Laser Technology ILT have come up with a striking new addition to contact stamping technologies in the ERDF research project ScanCut. In collaboration with industry partners from North Rhine-Westphalia, the Aachen-based team of researchers developed a hybrid manufacturing process for the laser cutting of thin-walled metal strips. This new process makes it possible to fabricate even the tiniest details of contact parts in an eco-friendly, high-precision and efficient manner.

Plug connectors are tiny and, at first glance, unremarkable – yet modern vehicles would be unable to function without them. Several thousand plug connectors...

Im Focus: New Strategy Against Osteoporosis

An international research team has found a new approach that may be able to reduce bone loss in osteoporosis and maintain bone health.

Osteoporosis is the most common age-related bone disease which affects hundreds of millions of individuals worldwide. It is estimated that one in three women...

Im Focus: AI & single-cell genomics

New software predicts cell fate

Traditional single-cell sequencing methods help to reveal insights about cellular differences and functions - but they do this with static snapshots only...

Im Focus: TU Graz Researchers synthesize nanoparticles tailored for special applications

“Core-shell” clusters pave the way for new efficient nanomaterials that make catalysts, magnetic and laser sensors or measuring devices for detecting electromagnetic radiation more efficient.

Whether in innovative high-tech materials, more powerful computer chips, pharmaceuticals or in the field of renewable energies, nanoparticles – smallest...

Im Focus: Tailored light inspired by nature

An international research team with Prof. Cornelia Denz from the Institute of Applied Physics at the University of Münster develop for the first time light fields using caustics that do not change during propagation. With the new method, the physicists cleverly exploit light structures that can be seen in rainbows or when light is transmitted through drinking glasses.

Modern applications as high resolution microsopy or micro- or nanoscale material processing require customized laser beams that do not change during...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“Conference on Laser Polishing – LaP 2020”: The final touches for surfaces

23.07.2020 | Event News

Conference radar for cybersecurity

21.07.2020 | Event News

Contact Tracing Apps against COVID-19: German National Academy Leopoldina hosts international virtual panel discussion

07.07.2020 | Event News

 
Latest News

Rare Earth Elements in Norwegian Fjords?

06.08.2020 | Earth Sciences

Anode material for safe batteries with a long cycle life

06.08.2020 | Power and Electrical Engineering

Turning carbon dioxide into liquid fuel

06.08.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>