Brain researchers discover the evolutionary traces ...( sonance imaging (fMRI) with humans. ...),Health

To this end, the scientists created artificial grammars with meaningless but structured syllables (e.g., de bo gi to). The ordering of these syllables was based upon either the simple rule ("local probability") or the complex rule ("hierarchy"). The syllables were divided into two categories. Syllables of category A ended with (in German) phonetically bright vowels (de, gi, le ), and category B with dark vowels (bo, fo, gu). The simple rule involved alternating sequences from categories A and B (e.g., AB AB = de bo gi ku); the complex rules on the other hand required hierarchies to link both categories (e.g., AA BB = de gi ku bo). This principle was meant to reduce grammar into the simplest formal rules. The advantage of experimenting with artificial grammars - as opposed to naturally spoken grammars - lies in the fact that other elements of language (semantics, phonology, morphology) do not have additional influences on neurological processing.

The participants were trained with both types of grammars two days before the scanning session. One group learned "local probability", the other "hierarchy". During the fMRI session, new syllable sequences were presented on a monitor that were either syntactically "right" (correct sequences) or "wrong" (incorrect sequences). This measured the ability of the subjects to use the rules they had learned as they evaluated each sequence as grammatically "right" or "wrong".

In the processing of both rule types, the researchers from Leipzig were able to show activity in a phylogenetically older brain area, the frontal operculum. As they had suspected, a younger brain structure, Broca's Area, showed activity only when the participants processed hierarchical rules.

In the second step, diffusion tensor imaging (DTI) was used to investigate the structural connectivity of the two brain regions. The result was that both areas were again clearly differentiated from each ot
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Contact: Profs. Angela D. Friederici und Jrg Bahlmann
bahlmann@cbs.mpg.de
49-341-9940-112
Max-Planck-Gesellschaft
16-Feb-2006