Publications

Abstract

Different frequency bands in the electroencephalogram are postulated to support distinct language functions. Studies have suggested
that alpha–beta power decreases may index word-retrieval processes. In context-driven word retrieval, participants hear
lead-in sentences that either constrain the final word (‘He locked the door with the’) or not (‘She walked in here with the’). The last
word is shown as a picture to be named. Previous studies have consistently found alpha–beta power decreases prior to picture
onset for constrained relative to unconstrained sentences, localised to the left lateral-temporal and lateral-frontal lobes. However,
the relative contribution of temporal versus frontal areas to alpha–beta power decreases is unknown. We recorded the electroencephalogram
from patients with stroke lesions encompassing the left lateral-temporal and inferior-parietal regions or left-lateral
frontal lobe and from matched controls. Individual participant analyses revealed a behavioural sentence context facilitation effect
in all participants, except for in the two patients with extensive lesions to temporal and inferior parietal lobes. We replicated the
alpha–beta power decreases prior to picture onset in all participants, except for in the two same patients with extensive posterior
lesions. Thus, whereas posterior lesions eliminated the behavioural and oscillatory context effect, frontal lesions did not. Hierarchical
clustering analyses of all patients’ lesion profiles, and behavioural and electrophysiological effects identified those two
patients as having a unique combination of lesion distribution and context effects. These results indicate a critical role for the left
lateral-temporal and inferior parietal lobes, but not frontal cortex, in generating the alpha–beta power decreases underlying context-
driven word production.

Abstract

Disagreement exists about how bilingual speakers select words, in particular, whether words in another language compete, or competition is restricted to a target language, or no competition occurs. Evidence that competition occurs but is restricted to a target language comes from response time (RT) effects obtained when speakers name pictures in one language while trying to ignore distractor words in another language. Compared to unrelated distractor words, RT is longer when the picture name and distractor are semantically related, but RT is shorter when the distractor is the translation of the name of the picture in the other language. These effects suggest that distractor words from another language do not compete themselves but activate their counterparts in the target language, thereby yielding the semantic interference and translation facilitation effects. Here, we report an event-related brain potential (ERP) study testing the prediction that priming underlies both of these effects. The RTs showed semantic interference and translation facilitation effects. Moreover, the picture-word stimuli yielded an N400 response, whose amplitude was smaller on semantic and translation trials than on unrelated trials, providing evidence that interference and facilitation priming underlie the RT effects. We present the results of computer simulations showing the utility of a within-language competition account of our findings.

Abstract

Whereas it has long been assumed that competition plays a role in lexical selection in word production (e.g., Levelt, Roelofs, & Meyer, 1999), recently Finkbeiner and Caramazza (2006) argued against the competition assumption on the basis of their observation that visible distractors yield semantic interference in picture naming, whereas masked distractors yield semantic facilitation. We examined an alternative account of these findings that preserves the competition assumption. According to this account, the interference and facilitation effects of distractor words reflect whether or not distractors are strong enough to exceed a threshold for entering the competition process. We report two experiments in which distractor strength was manipulated by means of coactivation and visibility. Naming performance was assessed in terms of mean response time (RT) and RT distributions. In Experiment 1, with low coactivation, semantic facilitation was obtained from clearly visible distractors, whereas poorly visible distractors yielded no semantic effect. In Experiment 2, with high coactivation, semantic interference was obtained from both clearly and poorly visible distractors. These findings support the competition threshold account of the polarity of semantic effects in naming.

Abstract

Picture–word interference is a widely employed paradigm to investigate lexical access in word production: Speakers name pictures while trying to ignore superimposed distractor words. The distractor can be congruent to the picture (pictured cat, word cat), categorically related (pictured cat, word dog), or unrelated (pictured cat, word pen). Categorically related distractors slow down picture naming relative to unrelated distractors, the so-called semantic interference. Categorically related distractors slow down picture naming relative to congruent distractors, analogous to findings in the colour–word Stroop task. The locus of semantic interference and Stroop-like effects in naming performance has recently become a topic of debate. Whereas some researchers argue for a pre-lexical locus of semantic interference and a lexical locus of Stroop-like effects, others localise both effects at the lexical selection stage. We investigated the time course of semantic and Stroop-like interference effects in overt picture naming by means of event-related potentials (ERP) and time–frequency analyses. Moreover, we employed cluster-based permutation for statistical analyses. Naming latencies showed semantic and Stroop-like interference effects. The ERP waveforms for congruent stimuli started diverging statistically from categorically related stimuli around 250 ms. Deflections for the categorically related condition were more negative-going than for the congruent condition (the Stroop-like effect). The time–frequency analysis revealed a power increase in the beta band (12–30 Hz) for categorically related relative to unrelated stimuli roughly between 250 and 370 ms (the semantic effect). The common time window of these effects suggests that both semantic interference and Stroop-like effects emerged during lexical selection.