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 journal 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 avai
'"/>

Contact: Gernot Supp
g.supp@uke.uni-hamburg.de
Public Library of Science
5-Aug-2007