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 eng
Contact: Gernot Supp
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