Brain electrical mechanisms of bilingual speech management: an initial investigation.

This exploratory study deals with EEG changes in 3 professional interpreters while mentally interpreting from their mother language into foreign languages and vice versa. EEGs were recorded while interpreting and compared with the periods at rest between these periods of interpreting. Significant (P < 0.05) changes of coherence between all pairs of electrodes with respect to the averaged EEG at rest were computed for 5 frequency bands between 4 and 32 Hz. The verbal tasks were control-compared with comparable coherence measures for mental arithmetic and listening to music. Interindividual differences predominated, but certain common characteristics of the EEG measures were also found. The temporal regions were most involved in interpreting and particularly in the uppermost beta band (24-32 Hz). More coherence increases--particularly in the right hemisphere--were found while interpreting into the foreign than into the native language. Coherence changes were found to accumulate in certain regions of the scalp as pivots or focal areas which apparently have functional significance for the task in question as nodal points of information exchange and/or transfer. Such pivots were found in T3 more than in T4 (in the right-handers) and vice versa in a left-hander. Theta and alpha bands behaved differently and did not show such clear-cut differences. The results during mental arithmetic and listening to music were different from the ones while interpreting. The results give support to the conception of the cortex as a network serving the greatest possible divergence and convergence of signals.