SUCCESSIVE ACTIVATION OF BOTH CEREBRAL HEMISPHERES DURING CUED WORD GENERATION

MOST humans have a left hemispheric dominance for language. However, d uring diagnostic language testing there also is activation of the righ t hemisphere, which is probably related to attention. To investigate f urther the role of attention during language production we monitored c erebral blood flow velocities in the middle cerebral arteries by conti nuous bilateral transcranial Doppler ultrasonography (TCD) in nine rig ht-handed subjects. During cued word generation, a successive activati on of the right hemisphere in the preparatory phase, and of the left h emisphere during word searching was demonstrated. These findings indic ate that attentional processes precede verbal activation and that the two procedures can be separated by comparative blood flow velocity mea surement.