Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Clock for brain waves

19.11.2014

Inhibitory neurons and electrical synapses determine the frequency of rhythmic activity in the brain

Oscillations of brain activity influence our attention and many other mental functions. Tatjana Tchumatchenko from the Max Planck Institute for Brain Research in Frankfurt and Claudia Clopath from Imperial College London have now developed a theoretical model that explains the origin of such oscillations in neural networks.


Netzwerk aus Nervenzellen in der Hirnrinde (Federn: elektrische Synapsen, Linien: chemische Synapsen). Die elektrischen Synapsen sind wichtig für rhythmische Netzwerk-weite Aktivitätsschwankungen.

© MPI f. Hirnforschung/ T. Tchumatchenko

Inhibitory neurons and electrical synapses play key roles and could therefore serve as targets for new drugs.

Alpha and gamma brain waves, which are visualized by means of electroencephalography (EEG) measurements, can provide doctors with information about a patient’s mental state for diagnostic purposes.

The mysterious term “brain waves” denotes nothing more than synchronous oscillations in the activity of groups of neurons that are often spread over large parts of the brain. The Greek letters indicate the oscillation frequency, which ranges from one hertz for alpha waves to several hundred hertz for theta waves. The waves act as a clock for the human brain and control attention, perception and memory formation.

The results of numerous experimental studies have shown that certain classes of neurons exert greater influence on network oscillations than others. Inhibitory neurons, which make up about 20 percent of the nerve cells in the cerebral cortex, appear to play a key role in the generation of brain waves.

However, it is unknown how inhibitory neurons control these oscillations. Because brain waves are a network phenomenon, it is also not clear how the properties of individual cells are reflected in network dynamics, or whether only synaptic connections are important.

Tatjana Tchumatchenko from the Max Planck Institute for Brain Research in Frankfurt and Claudia Clopath from Imperial College London are convinced that mathematics can deepen our understanding of the phenomenon of brain waves. In their joint work, they developed a mathematical framework that models the activity of excitatory and inhibitory neurons in a network such as the human cerebral cortex.

“We are able to reliably reproduce results from previous experiments using an analytical and numeric approach and our mathematical model has revealed two new conditions essential for the emergence of brain waves,” says Tatjana Tchumatchenko. “First, the individual inhibitory neurons must exhibit subthreshold resonance of the membrane potential at the preferred network oscillation frequency, i.e. they have to oscillate in time, although their electrical impulses do not necessarily reveal this oscillation.”

But the type of synaptic connectivity is also important, as oscillations occur only if the inhibitory neurons are interlinked by electrical synapses of sufficient connection strength.

Until recently, electrical synapses in the cerebral cortex were largely unknown, but are now known to occur in many areas of the brain. However, only inhibitory neurons are electrically coupled. This type of signal transmission has not been observed between excitatory neurons.

Inhibitory neurons and their synaptic connections therefore play a central role, say the researchers: “Amazingly, our model shows that the oscillation frequency of the entire network is determined only by the properties of inhibitory neurons and their connections, despite the fact that the majority of neurons are of the excitatory type,” says Claudia Clopath. “Of course,” she adds, “the properties of excitatory neurons help shape the dynamics of the network, but they only determine the amplitude of brain waves, not their frequency of oscillation.”

The knowledge gained will advance our understanding of complex systems and help explain the interplay between single network units and the arising network dynamics. The research results may also contribute to the development of more targeted drugs that could improve the chances for successful treatment in psychiatric care.


Contact

Amadeus Dettner
Max Planck Institute for Brain Research, Frankfurt am Main

Email: amadeus.dettner@brain.mpg.de

 
Dr. Tatjana Tchumatchenko
Max Planck Institute for Brain Research, Frankfurt am Main

Email: tatjana.tchumatchenko@brain.mpg.de


Original publication
Tatjana Tchumatchenko und Claudia Clopath

Oscillations emerging from noise-driven steady state in networks with electrical synapses and subthreshold resonance

Nature Communications, 18 November 2014

Amadeus Dettner | Max-Planck-Institute
Further information:
http://www.mpg.de/8764344/brain-waves-clock

More articles from Life Sciences:

nachricht Topologische Quantenchemie
21.07.2017 | Max-Planck-Institut für Chemische Physik fester Stoffe

nachricht Topological Quantum Chemistry
21.07.2017 | Max-Planck-Institut für Chemische Physik fester Stoffe

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

Im Focus: Laser-cooled ions contribute to better understanding of friction

Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision

Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

NASA looks to solar eclipse to help understand Earth's energy system

21.07.2017 | Earth Sciences

Stanford researchers develop a new type of soft, growing robot

21.07.2017 | Power and Electrical Engineering

Vortex photons from electrons in circular motion

21.07.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>