In this study, we investigated semantic context effects in language production with event-related brain potentials, extracted from the ongoing EEG recorded during overt speech production. We combined the picture-word interference paradigm and the semantic blocking paradigm to investigate the temporal dynamics and functional loci of semantic facilitation and interference effects. Objects were named in the context of semantically homogeneous blocks consisting of related objects and heterogeneous blocks consisting of unrelated objects. In each blocking condition, semantically related and unrelated distractor words were presented. Results show that classic patterns of semantically induced facilitation and interference effects in RTs can be directly related to ERP modulations located at temporal and frontal sites, starting at about 200 msec. Results also suggest that the processes associated with semantic facilitation and interference effects (i.e., conceptual and lexical processing) are highly interactive and coincide in time. Implications for the use of event-related brain potentials in speech production research and implications for current models of speech production are discussed.

Heterogeneous effects of semantic distance in language production have sparked a debate on the central assumption of many language production models, namely that lexical selection is a competitive process. In the present ERP study, we manipulated semantic distance in the picture word interference (PWI) paradigm systematically within taxonomic hierarchies. Target-distractor pairs were either closely related members of the same basic level category, hence sharing many semantic features (e.g., orangutan and gorilla), or distantly related members of the same superordinate category, sharing fewer features (e.g., orangutan and horse). Across related conditions, broad category membership (e.g., animals) was kept constant. Naming times reflected a systematic increase of semantic interference as semantic distance decreased. Early and later ERP modulations related to the semantic distance manipulation were observed at posterior regions starting at 234 ms and with an additional fronto-central cluster starting at 346 ms. Early effects are interpreted as indexing lexical selection while the late effects may reflect an N400-like component. Taking the behavioral and ERP modulations together, these results are in line with models of lexical selection that include an early competitive lexical selection process. (PsycINFO Database Record

In the present study we investigate the communication of different large scale brain sites during an overt language production task with state of the art methods for the estimation of EEG functional connectivity. Participants performed a semantic blocking task in which objects were named in semantically homogeneous blocks of trials consisting of members of a semantic category (e.g., all objects are tools) or in heterogeneous blocks, consisting of unrelated objects. The classic pattern of slower naming times in the homogeneous relative to heterogeneous blocks is assumed to reflect the duration of lexical selection. For the collected data in the homogeneous and heterogeneous conditions the imaginary part of coherency (ImC) was evaluated at different frequencies. The ImC is a measure for detecting the coupling of different brain sites acting on sensor level. Most importantly, the ImC is robust to the artifact of volume conduction. We analyzed the ImC at all pairs of 56 EEG channels across all frequencies. Contrasting the two experimental conditions we found pronounced differences in the theta band at 7 Hz and estimated the most dominant underlying brain sources via a minimum norm inverse solution based on the ImC. As a result of the source localization, we observed connectivity between occipito-temporal and frontal areas, which are well-known to play a major role in lexical-semantic language processes. Our findings demonstrate the feasibility of investigating interactive brain activity during overt language production.

Overt articulation produces strong artifacts in the electroencephalogram and in event-related potentials (ERPs), posing a serious problem for investigating language production with these variables. Here we describe the properties of articulation-related artifacts and propose a novel correction procedure. Experiment 1 co-recorded ERPs and trajectories of the articulators with an electromagnetic articulograph from a single participant. The generalization of the findings from the single participant to standard picture naming was investigated in Experiment 2. Both experiments provided evidence that articulation-induced artifacts may start up to 300 ms or more prior to voice onset or voice key onset-depending on the specific measure; they are highly similar in topography across many different phoneme patterns and differ mainly in their time course and amplitude. ERPs were separated from articulation-related artifacts with residue iteration decomposition (RIDE). After obtaining the artifact-free ERPs, their correlations with the articulatory trajectories dropped near to zero. Artifact removal with independent component analysis was less successful; while correlations with the articulatory movements remained substantial, early components prior to voice onset were attenuated in reconstructed ERPs. These findings offer new insights into the nature of articulation artifacts; together with RIDE as method for artifact removal the present report offers a fresh perspective for ERP studies requiring overt articulation.

Semantic interference effects in the picture-word interference (PWI) paradigm have long been assumed to reflect competitive mechanisms during lexical selection, a core component of the speech production system. However, recent observations of facilitative effects have cast doubt on the usefulness of the paradigm for investigating lexicalization, and on the existence of lexical competition in general. An alternative proposal suggests that lexical selection is not by competition, and that interference effects reflect articulatory processes outside the lexical system. Here, we contrast these theoretical alternatives with semantic distractor effects in the PWI paradigm. In two tasks, pictures were either overtly named or the names were manually classified. Interference effects of comparable magnitude were observed in both response modalities, regardless of whether the names were articulated or not. This finding supports lexical competition models and suggests that the articulators are not the source of interference in the PWI paradigm. Supplemental materials for this article may be downloaded from http://pbr.psychonomic-journals.org/content/supplemental.