Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Human knowledge is based upon directed connectivity between brain areas: How dynamic brain networks enable object recognition

06.08.2007
Which brain processes enable humans to rapidly access their personal knowledge? What happens if humans perceive either familiar or unfamiliar objects? The answer to these questions may lie in the direction of information flow transmitted between specialized brain areas that together establish a dynamic cortical network. This finding is reported in the latest issue of the scientific magazine PLoS ONE published on August 1st, 2007 [http://www.plosone.org/doi/pone.0000684].

Fruit or vegetable, insect or bird, familiar or unfamiliar – humans are used to classify objects in the world around them and group them into categories that have been formed and shaped constantly through every day's experience. Categorization during visual perception is exceptionally fast. Within just a fraction of a second we effortlessly access object-based knowledge, in particular if sufficient sensory information is available and the respective category is distinctly characterized by object features.

The precise neural mechanisms behind this brain function are currently not well understood. Several theoretical models are available, but empirical data and detailed measurements of brain processes in humans are still rare. In the last years of research evidence has accumulated to regard the brain as a parallel system with highly specialized compartments, so that different processing stages take place at different brain sites. According to the prominent theory of neuronal synchronization, cooperation between different brain areas is realized through synchronization of their rhythmic activity (30-100 Hz) leading to emergence of short-lasting dynamic networks.

An international team of scientists that includes biologists, engineers, physicists and psychologists has now investigated this network in humans by measuring electrical brain currents (EEG) and by applying the most advanced analysis techniques currently available.

”Human knowledge is definitely not stored in one single brain area. Access to knowledge results from the cooperation of several brain areas that jointly build a dynamic brain network. In this study we were not only able to confirm that recognition of familiar and unfamiliar objects activates a set of distributed brain areas. Rather, importantly, for the first time we have measured in humans how brain areas communicate with each other by directed information transfer, depending whether object-specific knowledge was available or not,' tells co-author and initiator of the study, Thomas Gruber of the Department of Psychology of the University of Leipzig.

The participants in Gruber's study were asked to categorize objects that were subsequently presented on a screen either as familiar or unfamiliar during the registration of their brain waves (EEG). Unfamiliar objects represented complex visual patterns, physically resembling the familiar ones in every possible way, except for familiarity. Familiar objects represented objects of every day's life such as cup, dog or violin. Actually, in the experiment only the factor familiarity was manipulated. Both conditions just differed in the possibility of the subjects to access specific, object-related knowledge in the course of recognition.

Based on previous studies the scientists expected to find not only a different level of brain activation in a set of distributed areas but also a different number of interactions between these areas.

“We expected that a larger number of brain interactions, a stronger degree of connectivity occurs, whenever a perceived object is familiar, that is whenever specific knowledge is available and can be used for processing. The contribution of our study is that by using a new method of signal analysis we succeeded in measuring the directionality of neuronal interactions. Cooperating brain areas forming a dynamic network are not just connected, but rather each area can be engaged either in receiving or sending signals or both. Until now this has been difficult to investigate, but our analysis suggests that most areas are involved in both during access to object-related knowledge,” states first author Gernot Supp with the Department of Neurophysiology, University Medical Center Hamburg-Eppendorf and the Max-Planck Institute of Human Cognitive and Brain Science, Leipzig, Germany.

“Traditional methods of analysis are insensitive to the true directionality of information flow. Here, for the first time, we investigated object recognition in humans by applying a new method, which in fact represents a measure of causality. With this measure, we were able to distinguish between feed-forward and feed-backward information flow and quantified the interaction between brain areas in greater detail”, reports Alois Schlögl, expert for biomedical signal processing at the University of Technology Graz, Austria and at the Fraunhofer Institute Berlin. He has made this new type of coupling analysis freely available for the scientific community in his open-source software-project BioSig (http://biosig.sf.net).

Together with the new method of directional coupling analysis these results may open a new perspective on brain processes. For the accurate execution of brain functions it might be crucial not only which brain areas are involved but, perhaps even more importantly, how they cooperate with each other. The investigation of this new dimension in brain research is just beginning.

The results are published in the August 1st issue of the online, open-access journal PloS ONE.

Andrew Hyde | alfa
Further information:
http://www.plosone.org
http://biosig.sf.net
http://www.plosone.org/doi/pone.0000684

More articles from Health and Medicine:

nachricht A promising target for kidney fibrosis
21.04.2017 | Brigham and Women's Hospital

nachricht Stem cell transplants: activating signal paths may protect from graft-versus-host disease
20.04.2017 | Technische Universität München

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

NASA's Fermi catches gamma-ray flashes from tropical storms

25.04.2017 | Physics and Astronomy

Researchers invent process to make sustainable rubber, plastics

25.04.2017 | Materials Sciences

Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017

25.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>