The semantic interference effect in the picture-word paradigm: An event-related fMRI study employing overt responses

We used event-related functional magnetic resonance imaging (fMRI) to inves tigate neural responses associated with the semantic interference (SI) effe ct in the picture-word task. Independent stage models of word production as sume that the locus of the SI effect is at the conceptual processing level (Levelt et al. [1999]: Behav Brain Sci 22:1-75), whereas interactive models postulate that it occurs at phonological retrieval (Starreveld and La Heij [1996]: J Exp Psychol Learn Mem Cogn 22:896-918). In both types of model r esolution of the SI effect occurs as a result of competitive, spreading act ivation without the involvement of inhibitory links. These assumptions were tested by randomly presenting participants with trials from semantically-r elated and lexical control distractor conditions and acquiring image volume s coincident with the estimated peak hemodynamic response for each trial. O vert vocalization of picture names occurred in the absence of scanner noise , allowing reaction time (RT) data to be collected. Analysis of the RT data confirmed the SI effect. Regions showing differential hemodynamic response s during the SI effect included the left mid section of the middle temporal gyrus, left posterior superior temporal gyrus, left anterior cingulate cor tex, and bilateral orbitomedial prefrontal cortex. Additional responses wer e observed in the frontal eye fields, left inferior parietal lobule, and ri ght anterior temporal and occipital cortex. The results are interpreted as indirectly supporting interactive models that allow spreading activation be tween both conceptual processing and phonological retrieval levels of word production. In addition, the data confirm that selective attention/response suppression has a role in resolving the SI effect similar to the way in wh ich Stroop interference is resolved. We conclude that neuroimaging studies can provide information about the neuroanatomical organization of the lexic al system that may prove useful for constraining theoretical models of word production. (C) 2001 Wiley-Liss, Inc.