Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Hidden dynamics detected in neuronal networks

23.07.2019

Scientists from Forschungszentrum Jülich and RWTH Aachen University show that neuronal networks can assume a second, previously unknown critical mode

Neuronal networks in the brain can process information particularly well when they are close to a critical point - or so brain researchers had assumed based on theoretical considerations. However, experimental investigations of brain activity revealed much fewer indicators of such critical states than expected.


The heterogeneous, critical dynamics show no avalanche-like increase, instead manifesting in specific projections of nerve cell activity in which neurons are weighted differently -- which corresponds to a different degree of excitatory or inhibitory influence of individual neurons.

Copyright: Forschungszentrum Jülich / David Dahmen

Scientists from Forschungszentrum Jülich and RWTH Aachen University have now proposed a possible explanation. They showed that neuronal networks can assume a second, previously unknown critical mode whose hidden dynamics are almost impossible to measure with conventional methods.

Critical points, at which complex systems abruptly change their characteristics, are familiar concepts in physics. Ferromagnetic materials are one example.

Below the critical temperature, also known as the Curie temperature, the electron spins of the material align so that they all point in the same direction. The tiny magnetic moments of the individual spins thus add together, which can be measured from the outside as a spontaneous magnetization of the material.

Very similar dynamics were previously detected in measurements of brain activity. Brain signals are a typical case, where large areas of the network become active simultaneously in an avalanche-like fashion within a very short time.

Overall, however, the phenomenon occurs much more rarely than expected. Scientists from Forschungszentrum Jülich and RWTH Aachen University have now presented a solution for this apparent contradiction in the journal PNAS. They showed that neuronal networks can exhibit a second, previously unknown type of criticality.

An analysis of the simultaneous activity of 155 nerve cells showed that for this second type of criticality, a large number of nerve cells also exhibit coordinated behaviour.

However, the interaction comprises not only the simultaneous activation but also the targeted inhibition of large groups of neurons. This newly discovered criticality permits the network to represent signals in numerous combinations of activated neurons and therefore - according to the researchers - to efficiently process information in parallel.

This also explains why no sudden increase in network activity can be detected from the outside. Standard methods such as EEG or LFP essentially add the signals of many neurons together. In this second critical state, however, the number of active nerve cells remains mostly constant.

The heterogeneous dynamics can therefore not be recorded with these methods. Only by using highly developed mathematical methods borrowed from statistical physics could the researchers, headed by Prof. Moritz Helias, make experimentally verifiable predictions of the correlations between the nerve cells.

For the direct experimental detection of the network state they had predicted by means of theory and simulation, the researchers, working with lead author Dr. David Dahmen, drew on Prof. Sonja Grün's expertise in analysing the joint activity of many nerve cells.

"This study has a far-reaching impact in that Prof. Helias and his team succeeded in applying field theory, which is a very successful method in physics, to neuroscience. We can thus hope for further insights in future," explains institute head Prof. Markus Diesmann (INM-6). Diesmann plays a major role in the EU's Human Brain Project (HBP), one of the largest neuroscientific projects worldwide, which unites the work of 500 researchers in 19 EU member states.

"In the HBP, we are concerned with the technology required to simulate large parts of the brain with all their nerve cells. These simulations on their own do not yet yield insights, however. They simply result in simulated data which are just as complicated as the data from nature.

However, they allow us to modify networks in a much more targeted manner than would be possible using experimental methods. But only by simplifying them, in a controlled way, into manageable mathematical models with fewer equations will we have the potential to understand the underlying mechanisms," explains Diesmann.

Media Contact

Tobias Schlößer
t.schloesser@fz-juelich.de
49-246-161-4771

 @fz_juelich

http://www.fz-juelich.de 

Tobias Schlößer | EurekAlert!
Further information:
https://www.fz-juelich.de/SharedDocs/Pressemitteilungen/UK/EN/2019/notifications/2019-07-12-hidden-dynamics.html
http://dx.doi.org/10.1073/pnas.1818972116

Further reports about: Forschungszentrum Jülich data nerve cells neurons process information

More articles from Life Sciences:

nachricht New technique to determine protein structures may solve biomedical puzzles
12.12.2019 | Dana-Farber Cancer Institute

nachricht NTU Singapore scientists convert plastics into useful chemicals using su
12.12.2019 | Nanyang Technological University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Cheers! Maxwell's electromagnetism extended to smaller scales

More than one hundred and fifty years have passed since the publication of James Clerk Maxwell's "A Dynamical Theory of the Electromagnetic Field" (1865). What would our lives be without this publication?

It is difficult to imagine, as this treatise revolutionized our fundamental understanding of electric fields, magnetic fields, and light. The twenty original...

Im Focus: Highly charged ion paves the way towards new physics

In a joint experimental and theoretical work performed at the Heidelberg Max Planck Institute for Nuclear Physics, an international team of physicists detected for the first time an orbital crossing in the highly charged ion Pr⁹⁺. Optical spectra were recorded employing an electron beam ion trap and analysed with the aid of atomic structure calculations. A proposed nHz-wide transition has been identified and its energy was determined with high precision. Theory predicts a very high sensitivity to new physics and extremely low susceptibility to external perturbations for this “clock line” making it a unique candidate for proposed precision studies.

Laser spectroscopy of neutral atoms and singly charged ions has reached astonishing precision by merit of a chain of technological advances during the past...

Im Focus: Ultrafast stimulated emission microscopy of single nanocrystals in Science

The ability to investigate the dynamics of single particle at the nano-scale and femtosecond level remained an unfathomed dream for years. It was not until the dawn of the 21st century that nanotechnology and femtoscience gradually merged together and the first ultrafast microscopy of individual quantum dots (QDs) and molecules was accomplished.

Ultrafast microscopy studies entirely rely on detecting nanoparticles or single molecules with luminescence techniques, which require efficient emitters to...

Im Focus: How to induce magnetism in graphene

Graphene, a two-dimensional structure made of carbon, is a material with excellent mechanical, electronic and optical properties. However, it did not seem suitable for magnetic applications. Together with international partners, Empa researchers have now succeeded in synthesizing a unique nanographene predicted in the 1970s, which conclusively demonstrates that carbon in very specific forms has magnetic properties that could permit future spintronic applications. The results have just been published in the renowned journal Nature Nanotechnology.

Depending on the shape and orientation of their edges, graphene nanostructures (also known as nanographenes) can have very different properties – for example,...

Im Focus: Electronic map reveals 'rules of the road' in superconductor

Band structure map exposes iron selenide's enigmatic electronic signature

Using a clever technique that causes unruly crystals of iron selenide to snap into alignment, Rice University physicists have drawn a detailed map that reveals...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

The Future of Work

03.12.2019 | Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

 
Latest News

Weizmann physicists image electrons flowing like water

12.12.2019 | Physics and Astronomy

Revealing the physics of the Sun with Parker Solar Probe

12.12.2019 | Physics and Astronomy

New technique to determine protein structures may solve biomedical puzzles

12.12.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>