The separation of processing stages in a lexical interference fMRI-paradigm

In picture-word interference paradigms, the picture naming process is influenced by an additional presentation of linguistic distractors. Naming response times (RTs) are speeded (facilitation) by associatively-related and phonologically-related words when compared to unrelated words, while they are slowed down by categorically-related words (inhibition), given that distractor onsets occur at appropriate stimulus onset asynchronies (SOAs). In the present study with healthy subjects, we for the first time integrated all four auditorily presented distractor types into a single paradigm at an SOA of -200 ms, in order to directly compare behavioral and neural interference effects between them. The behavioral study corroborated results of previous studies and revealed that associatively-related distractors speeded RTs even more than phonologically-related distractors, thereby becoming equally fast as naming without distractors. Distractors were assumed to specifically enhance activation of brain areas corresponding to processing stages as determined in a cognitive model of word production (Indefrey, P., Levelt, W.J.M., 2004. The spatial and temporal signatures of word production components. Cognition 92, 101-144.). Functional magnetic resonance imaging (fMRI) at 3 T revealed activation of left superior temporal gyrus exclusively for phonologically-related distractors, and activation of left or right lingual gyrus exclusively for associatively-related and categorically-related distractors, respectively. Moreover, phonologically-related distractors elicited phonological-phonetic networks, and both semantic distractors evoked areas associated with mental imagery, semantics, and episodic memory retrieval and associations. While processes involved in distractor inhibition (e. g., conflict/competition monitoring) and high articulatory demands were observed for categorically-related distractors, priming of articulatory planning was revealed for associatively-related distractors. We conclude that activations of neural networks as obtained by the fMRI interference paradigm can be predicted from a cognitive model. (C) 2008 Elsevier Inc. All rights reserved.