FRONTAL-LOBE ACTIVATION DURING WORD GENERATION STUDIED BY FUNCTIONAL MRI

Aims - To further delimit the specific verbal operations occurring in the dorsolateral frontal cortex during the generation of words, method s different verbal fluency tasks guided by distinct specifications (ph onological, semantic, or automatic production of words) were used in a functional magnetic resonance study. The study group comprised 10 rig ht-handed normal subjects ranging in age from 23 to 27 years. Function al magnetic resonance images were obtained in a 1.5-Tesla magnet using a spoiled GRASS sequence. Results - Noticeable activation was found d uring the word generation tasks in the dorsolateral frontal cortex. Th e region showing the most prominent activation was the posterior part of the left middle frontal gyrus. Nevertheless, the different tasks ea ch had a different activation effect. The phonologically guided genera tion of words produced the most consistent activation of the middle fr ontal gyrus, which mainly involved the premotor cortex. Conclusion The results suggest that operations concerned with the generation of soun d sequences, rather than the amount of produced words or their semanti cs, are responsible for sustained focal activity observed in the front al lobes during verbal fluency tasks.