Lexical retrieval during fluent speech production: an fMRI study

We investigated the neural correlates of lexical retrieval during fluent sp eech production using MRI. Blood oxygenation level dependent (BOLD) contras t was measured while subjects spoke about 7 Rorschach inkblots for 3 min ea ch. Varying degrees of speech rate were elicited during each run. In a with in-subject design, the number of words produced was correlated with the BOL D contrast in the two runs in each subject that showed the highest variance of speech output. The rate of articulation was positively correlated with activation in the left superior temporal (BA 22) and supramarginal (BA 39/4 0) gyri. The main negative correlations were in the fusiform gyri bilateral ly (BA 19), the posterior cingulate (BA 30) and superior occipital gyrus (B A 19). Lexical retrieval during continuous language production engages area s in the left temporal and inferior parietal cortex. This pattern of activa tion differs from that evident during the generation of single words (verba l fluency), which is more associated with left prefrontal activation. Neuro Report 11:4093-4096 (C) 2000 Lippincott Williams & Wilkins.