Interference and facilitation in overt speech production investigated with event-related potentials

Behavioral and neural measures of semantic conflict monitoring: Findings from a novel picture-word interference task

Conflict monitoring has been studied extensively using experimental paradigms that manipulate perceptual dimensions of stimuli and responses. The picture-word interference (PWI) task has historically been used to examine semantic conflict, but primarily for the purpose of examining lexical retrieval. In this study, we utilized two novel PWI tasks to assess conflict monitoring in the context of semantic conflict. Participants included nineteen young adults (14F, age = 20.79 ± 3.14) who completed two tasks: Animals and Objects. Task and conflict effects were assessed by examining behavioral (reaction time and accuracy) and neurophysiological (oscillations in theta, alpha, and beta band) measures. Results revealed conflict effects within both tasks, but the pattern of findings differed across the two semantic categories. Participants were slower to respond to unmatched versus matched trials on the Objects task only and were less accurate responding to matched versus unmatched trials in the Animals task only. We also observed task differences, with participants responding more accurately on conflict trials for Animals compared to Objects. Differences in neural oscillations were observed, including between-task differences in low beta oscillations and within-task differences in theta, alpha, and low beta. We also observed significant correlations between task performance and standard measures of cognitive control. This work provides new insights into conflict monitoring, highlighting the importance of examining conflict across different semantic categories, especially in the context of animacy. The findings serve as a benchmark to assess conflict monitoring using PWI tasks across populations of varying cognitive ability.

Taxonomic and thematic semantic relationships in picture naming as revealed by Laplacian-transformed event-related potentials

Semantically related concepts co-activate when we speak. Prior research reported both behavioral interference and facilitation due to co-activation during picture naming. Different word relationships may account for some of this discrepancy. Taxonomically related words (e.g., WOLF-DOG) have been associated with semantic interference; thematically related words (e.g., BONE-DOG) have been associated with facilitation. Although these different semantic relationships have been associated with opposite behavioral outcomes, electrophysiological studies have found inconsistent effects on event-related potentials. We conducted a picture-word interference electroencephalography experiment to examine word retrieval dynamics in these different semantic relationships. Importantly, we used traditional monopolar analysis as well as Laplacian transformation allowing us to examine spatially deblurred event-related components. Both analyses revealed greater negativity (150-250 ms) for unrelated than related taxonomic pairs, though more restricted in space for thematic pairs. Critically, Laplacian analyses revealed a larger negative-going component in the 300 to 500 ms time window in taxonomically related versus unrelated pairs which were restricted to a left frontal recording site. In parallel, an opposite effect was found in the same time window but localized to a left parietal site. Finding these opposite effects in the same time window was feasible thanks to the use of the Laplacian transformation and suggests that frontal control processes are concurrently engaged with cascading effects of the spread of activation through semantically related representations.

The beauty of diversity in cognitive neuroscience: The case of sex-related effects in language production networks

Over the past few decades, several studies have focused on potential sex-related differences in the trajectories of language development and functioning. From a behavioral point of view, the available literature shows controversial results: differences between males and females in language production tasks may not always be detectable and, even when they are, are potentially biased by sociological and educational confounding factors. The problem regarding potential sex-related differences in language production has also been investigated at the neural level, again with controversial results. The current minireview focuses on studies assessing sex-related differences in the neural networks of language production. After providing a theoretical framework of language production, it is shown that the few available investigations have provided mixed results. The major reasons for discrepant findings are discussed with theoretical and methodological implications for future studies.

How to do Better N400 Studies: Reproducibility, Consistency and Adherence to Research Standards in the Existing Literature

Given the complexity of ERP recording and processing pipeline, the resulting variability of methodological options, and the potential for these decisions to influence study outcomes, it is important to understand how ERP studies are conducted in practice and to what extent researchers are transparent about their data collection and analysis procedures. The review gives an overview of methodology reporting in a sample of 132 ERP papers, published between January 1980 – June 2018 in journals included in two large databases: Web of Science and PubMed. Because ERP methodology partly depends on the study design, we focused on a well-established component (the N400) in the most commonly assessed population (healthy neurotypical adults), in one of its most common modalities (visual images). The review provides insights into 73 properties of study design, data pre-processing, measurement, statistics, visualization of results, and references to supplemental information across studies within the same subfield. For each of the examined methodological decisions, the degree of consistency, clarity of reporting and deviations from the guidelines for best practice were examined. Overall, the results show that each study had a unique approach to ERP data recording, processing and analysis, and that at least some details were missing from all papers. In the review, we highlight the most common reporting omissions and deviations from established recommendations, as well as areas in which there was the least consistency. Additionally, we provide guidance for a priori selection of the N400 measurement window and electrode locations based on the results of previous studies.

Morphological facilitation and semantic interference in compound production: An ERP study

This study investigates the production of nominal compounds (Experiment 1) and simple nouns (Experiment 2) in a picture-word interference (PWI) paradigm to test models of morpho-lexical representation and processing. The continuous electroencephalogram (EEG) was registered and event-related brain potentials [ERPs] were analyzed in addition to picture-naming latencies. Experiment 1 used morphologically and semantically related distractor words to tap into different pre-articulatory planning stages during compound production. Relative to unrelated distractors, naming was speeded when distractors corresponded to morphemes of the compound (sun or flower for the target sunflower), but slowed when distractors were from the same semantic category as the compound (tulip ➔ sunflower). Distractors from the same category as the compound's first constituent (moon ➔ sunflower) had no influence. The diverging effects for semantic and morphological distractors replicate results from earlier studies. ERPs revealed different effects of morphological and semantic distractors with an interesting time course: morphological effects had an earlier onset. Comparable to the naming latencies, no ERP effects were obtained for distractors from the same semantic category as the compound's first constituent. Experiment 2 investigated the effectiveness of the latter distractors, presenting them with pictures of the compounds' first constituents (e.g., moon ➔ sun). Interference was confirmed both behaviorally and in the ERPs, showing that the absence of an effect in Experiment 1 was not due to the materials used. Considering current models of speech production, the data are best explained by a cascading flow of activation throughout semantic, lexical and morpho-phonological steps of speech planning.

Can gesture observation help people with aphasia name actions?

It has been suggested that gesture can play a role in the treatment of naming impairments in aphasia, however investigation is still sparse, especially when compared to research on verbal treatments. Critically, previous studies have included either verbal or gesture production in the training. However, while in speakers without language impairment, action naming is facilitated by gesture observation, no study has yet systematically determined whether gesture observation alone influences word retrieval in people with aphasia. This is the aim of the research presented here. In a gesture priming experiment, participants with aphasia named actions that were preceded by the observation of videos of congruent or unrelated gestures or a non-gesture control condition. At the group-level, action naming was facilitated by observation of congruent gestures. However, single-case analyses revealed variability in the extent to which the participants benefited from gesture cueing. The potential mechanisms underlying the effects of gesture observation on action picture naming in people with aphasia were examined by exploring participant-related and item-related predictors of improvement. It is concluded that gesture observation may facilitate verb retrieval at either semantic or lexical levels. In addition, and despite variability across individuals, gesture observation seems more likely to facilitate action naming in people with spared gesture semantics and mild-moderate deficits in lexical-semantic or post-semantic processing.

The time course of colour congruency effects in picture naming

In our interactions with people and objects in the world around us, as well as in communicating our thoughts, we rely on the use of conceptual knowledge stored in long-term memory. From a frame-theoretic point of view, a concept is represented by a central node and recursive attribute-value structures further specifying the concept. The present study explores whether and how the activation of an attribute within a frame might influence access to the concept's name in language production, focussing on the colour attribute. Colour has been shown to contribute to object recognition, naming, and memory retrieval, and there is evidence that colour plays a different role in naming objects that have a typical colour (high colour-diagnostic objects such as tomatoes) than in naming objects without a typical colour (low colour-diagnostic objects such as bicycles). We report two behavioural experiments designed to reveal potential effects of the activation of an object's typical colour on naming the object in a picture-word interference paradigm. This paradigm was used to investigate whether naming is facilitated when typical colours are presented alongside the to-be-named picture (e.g., the word "red" superimposed on the picture of a tomato), compared to atypical colours (such as "brown"), unrelated adjectives (such as "fast"), or random letter strings. To further explore the time course of these potential effects, the words were presented at different time points relative to the to-be-named picture (Exp. 1: -400 ms, Exp. 2: -200 ms, 0 ms, and + 200 ms). By including both high and low colour-diagnostic objects, it was possible to explore whether the activation of a colour differentially affects naming of objects that have a strong association with a typical colour. The results showed that (pre-)activation of the appropriate colour attribute facilitated naming compared to an inappropriate colour. This was only the case for objects closely connected with a typical colour. Consequences of these findings for frame-theoretic accounts of conceptual representation are discussed.

Early and Late Effects of Semantic Distractors on Electroencephalographic Responses During Overt Picture Naming

This study investigated the nature of the interference effect of semantically related distractors in the picture-word interference paradigm, which has been claimed to be caused by either competition between lexical representations of target and distractor or by a late response exclusion mechanism that removes the distractor from a response buffer. EEG was recorded while participants overtly named pictures accompanied by categorically related versus unrelated written distractor words. In contrast to previous studies, stimuli were presented for only 250 ms to avoid any re-processing. ERP effects of relatedness were found around 290, 470, 540, and 660 ms post stimulus onset. In addition, related distractors led to an increase in midfrontal theta power, especially from about 440 to 540 ms, as well as to decreased high beta power between 40 and 110 ms and increased high beta power between 275 and 340 ms post stimulus onset. Response-locked analyses showed no differences in ERPs, however increased low and high beta power for related distractors in various time windows, most importantly a high beta power increase between -175 and -155 ms before speech onset. These results suggest that the semantic distractor effect is a combination of various effects and that the lexical competition account and the response exclusion account each capture a part, but not all aspects of the effect.

Morphological encoding beyond slots and fillers: An ERP study of comparative formation in English

One important organizational property of morphology is competition. Different means of expression are in conflict with each other for encoding the same grammatical function. In the current study, we examined the nature of this control mechanism by testing the formation of comparative adjectives in English during language production. Event-related brain potentials (ERPs) were recorded during cued silent production, the first study of this kind for comparative adjective formation. We specifically examined the ERP correlates of producing synthetic relative to analytic comparatives, e.g. angrier vs. more angry. A frontal, bilaterally distributed, enhanced negative-going waveform for analytic comparatives (vis-a-vis synthetic ones) emerged approximately 300ms after the (silent) production cue. We argue that this ERP effect reflects a control mechanism that constrains grammatically-based computational processes (viz. more comparative formation). We also address the possibility that this particular ERP effect may belong to a family of previously observed negativities reflecting cognitive control monitoring, rather than morphological encoding processes per se.

When Wine and Apple Both Help the Production of Grapes: ERP Evidence for Post-lexical Semantic Facilitation in Picture Naming

Background: Producing a word in referential naming requires to select the right word in our mental lexicon among co-activated semantically related words. The mechanisms underlying semantic context effects during speech planning are still controversial, particularly for semantic facilitation which investigation remains under-represented in contrast to the plethora of studies dealing with interference. Our aim is to study the time-course of semantic facilitation in picture naming, using a picture-word "interference" paradigm and event-related potentials (ERPs). Methods: We compared two different types of semantic relationships, associative and categorical, in a single word priming and a double word priming paradigm. The primes were presented visually with a long negative Stimulus Onset Asynchrony (SOA), which is expected to cause facilitation. Results: Shorter naming latencies were observed after both associative and categorical primes, as compared to unrelated primes, and even shorter latencies after two primes. Electrophysiological results showed relatively late modulations of waveform amplitudes for both types of primes (beginning ~330 ms post picture onset with a single prime and ~275 ms post picture onset with two primes), corresponding to a shift in latency of similar topographic maps across conditions. Conclusion: The present results are in favor of a post-lexical locus of semantic facilitation for associative and categorical priming in picture naming and confirm that semantic facilitation is as relevant as semantic interference to inform on word production. The post-lexical locus argued here might be related to self-monitoting or/and to modulations at the level of word-form planning, without excluding the participation of strategic processes.

Dutch-Cantonese Bilinguals Show Segmental Processing during Sinitic Language Production

This study addressed the debate on the primacy of syllable vs. segment (i.e., phoneme) as a functional unit of phonological encoding in syllabic languages by investigating both behavioral and neural responses of Dutch-Cantonese (DC) bilinguals in a color-object picture naming task. Specifically, we investigated whether DC bilinguals exhibit the phonemic processing strategy, evident in monolingual Dutch speakers, during planning of their Cantonese speech production. Participants named the color of colored line-drawings in Cantonese faster when color and object matched in the first segment than when they were mismatched (e.g., 藍駱駝, /laam4/ /lok3to4/, “blue camel;” 紅饑駝, /hung4/ /lok3to4/, “red camel”). This is in contrast to previous studies in Sinitic languages that did not reveal such phoneme-only facilitation. Phonemic overlap also modulated the event-related potentials (ERPs) in the 125–175, 200–300, and 300–400 ms time windows, suggesting earlier ERP modulations than in previous studies with monolingual Sinitic speakers or unbalanced Sinitic-Germanic bilinguals. Conjointly, our results suggest that, while the syllable may be considered the primary unit of phonological encoding in Sinitic languages, the phoneme can serve as the primary unit of phonological encoding, both behaviorally and neurally, for DC bilinguals. The presence/absence of a segment onset effect in Sinitic languages may be related to the proficiency in the Germanic language of bilinguals.

Electrophysiological characterization of facilitation and interference in the picture-word interference paradigm

The picture-word interference paradigm is often used to investigate the processes underlying word production. In this paradigm, participants name pictures while ignoring distractor words. The aim of this study is to investigate the processes underlying this task and how/when they differ from those involved in simple picture naming. It examines the electrophysiological signature of general interference (longer response times with than without distractors) and facilitation (shorter response times for distractor-word stimuli overlapping in phonemes/orthography) effects. Mass univariate analyses are used to determine the temporal boundaries and spatial distribution of these effects without a priori restrictions in the time/space dimensions. Topographic pattern analyses complement this information by indicating whether (and when) the neural networks differ across conditions. Results suggest that the general interference effect has two loci, the grammatical encoding and the phonological encoding of the target word, with different neural networks involved in the two tasks during part of the grammatical encoding process. Furthermore, the electrophysiological signature of interference and facilitation effects in the time window of phonological encoding is highly similar, suggesting that the two effects could result from the same underlying mechanism. These findings are discussed in the light of existing accounts of interference and facilitation effects.

The Temporal Courses of Phonological and Orthographic Encoding in Handwritten Production in Chinese: An ERP Study

A central issue in written production concerns how phonological codes influence the output of orthographic codes. We used a picture-word interference paradigm combined with the event-related potential technique to investigate the temporal courses of phonological and orthographic activation and their interplay in Chinese writing. Distractors were orthographically related, phonologically related, orthographically plus phonologically related, or unrelated to picture names. The behavioral results replicated the classic facilitation effect for all three types of relatedness. The ERP results indicated an orthographic effect in the time window of 370–500 ms (onset latency: 370 ms), a phonological effect in the time window of 460–500 ms (onset latency: 464 ms), and an additive pattern of both effects in both time windows, thus indicating that orthographic codes were accessed earlier than, and independent of, phonological codes in written production. The orthographic activation originates from the semantic system, whereas the phonological effect results from the activation spreading from the orthographic lexicon to the phonological lexicon. These findings substantially strengthen the existing evidence that shows that access to orthographic codes is not mediated by phonological information, and they provide important support for the orthographic autonomy hypothesis.

Temporal dynamics of sensorimotor integration in speech perception and production: independent component analysis of EEG data

Activity in anterior sensorimotor regions is found in speech production and some perception tasks. Yet, how sensorimotor integration supports these functions is unclear due to a lack of data examining the timing of activity from these regions. Beta (~20 Hz) and alpha (~10 Hz) spectral power within the EEG μ rhythm are considered indices of motor and somatosensory activity, respectively. In the current study, perception conditions required discrimination (same/different) of syllables pairs (/ba/ and /da/) in quiet and noisy conditions. Production conditions required covert and overt syllable productions and overt word production. Independent component analysis was performed on EEG data obtained during these conditions to (1) identify clusters of μ components common to all conditions and (2) examine real-time event-related spectral perturbations (ERSP) within alpha and beta bands. 17 and 15 out of 20 participants produced left and right μ-components, respectively, localized to precentral gyri. Discrimination conditions were characterized by significant (pFDR < 0.05) early alpha event-related synchronization (ERS) prior to and during stimulus presentation and later alpha event-related desynchronization (ERD) following stimulus offset. Beta ERD began early and gained strength across time. Differences were found between quiet and noisy discrimination conditions. Both overt syllable and word productions yielded similar alpha/beta ERD that began prior to production and was strongest during muscle activity. Findings during covert production were weaker than during overt production. One explanation for these findings is that μ-beta ERD indexes early predictive coding (e.g., internal modeling) and/or overt and covert attentional/motor processes. μ-alpha ERS may index inhibitory input to the premotor cortex from sensory regions prior to and during discrimination, while μ-alpha ERD may index sensory feedback during speech rehearsal and production.

Real-time processing in picture naming in adults who stutter: ERP evidence

OBJECTIVE

The aim was to compare real-time language/cognitive processing in picture naming in adults who stutter (AWS) versus typically-fluent adults (TFA).

METHODS

Participants named pictures preceded by masked prime words. Primes and target picture labels were identical or mismatched. Priming effects on naming and picture-elicited ERP activity were analyzed. Vocabulary knowledge correlations with these measures were assessed.

RESULTS

Priming improved naming RTs and accuracy in both groups. RTs were longer for AWS, and correlated positively with receptive vocabulary in TFA. Electrophysiologically, posterior-P1 amplitude negatively correlated with expressive vocabulary in TFA versus receptive vocabulary in AWS. Frontal/temporal-P1 amplitude correlated positively with expressive vocabulary in AWS. Identity priming enhanced frontal/posterior-N2 amplitude in both groups, and attenuated P280 amplitude in AWS. N400 priming was topographically-restricted in AWS.

CONCLUSIONS

Results suggest that conceptual knowledge was perceptually-grounded in expressive vocabulary in TFA versus receptive vocabulary in AWS. Poorer expressive vocabulary in AWS was potentially associated with greater suppression of irrelevant conceptual information. Priming enhanced N2-indexed cognitive control and visual attention in both groups. P280-indexed focal attention attenuated with priming in AWS only. Topographically-restricted N400 priming suggests that lemma/word form connections were weaker in AWS.

SIGNIFICANCE

Real-time language/cognitive processing in picture naming operates differently in AWS.

Twisting tongues to test for conflict-monitoring in speech production

A number of recent studies have hypothesized that monitoring in speech production may occur via domain-general mechanisms responsible for the detection of response conflict. Outside of language, two ERP components have consistently been elicited in conflict-inducing tasks (e.g., the flanker task): the stimulus-locked N2 on correct trials, and the response-locked error-related negativity (ERN). The present investigation used these electrophysiological markers to test whether a common response conflict monitor is responsible for monitoring in speech and non-speech tasks. Electroencephalography (EEG) was recorded while participants performed a tongue twister (TT) task and a manual version of the flanker task. In the TT task, people rapidly read sequences of four nonwords arranged in TT and non-TT patterns three times. In the flanker task, people responded with a left/right button press to a center-facing arrow, and conflict was manipulated by the congruency of the flanking arrows. Behavioral results showed typical effects of both tasks, with increased error rates and slower speech onset times for TT relative to non-TT trials and for incongruent relative to congruent flanker trials. In the flanker task, stimulus-locked EEG analyses replicated previous results, with a larger N2 for incongruent relative to congruent trials, and a response-locked ERN. In the TT task, stimulus-locked analyses revealed broad, frontally-distributed differences beginning around 50 ms and lasting until just before speech initiation, with TT trials more negative than non-TT trials; response-locked analyses revealed an ERN. Correlation across these measures showed some correlations within a task, but little evidence of systematic cross-task correlation. Although the present results do not speak against conflict signals from the production system serving as cues to self-monitoring, they are not consistent with signatures of response conflict being mediated by a single, domain-general conflict monitor.

Distinct patterns of brain activity characterise lexical activation and competition in spoken word production

According to a prominent theory of language production, concepts activate multiple associated words in memory, which enter into competition for selection. However, only a few electrophysiological studies have identified brain responses reflecting competition. Here, we report a magnetoencephalography study in which the activation of competing words was manipulated by presenting pictures (e.g., dog) with distractor words. The distractor and picture name were semantically related (cat), unrelated (pin), or identical (dog). Related distractors are stronger competitors to the picture name because they receive additional activation from the picture relative to other distractors. Picture naming times were longer with related than unrelated and identical distractors. Phase-locked and non-phase-locked activity were distinct but temporally related. Phase-locked activity in left temporal cortex, peaking at 400 ms, was larger on unrelated than related and identical trials, suggesting differential activation of alternative words by the picture-word stimuli. Non-phase-locked activity between roughly 350-650 ms (4-10 Hz) in left superior frontal gyrus was larger on related than unrelated and identical trials, suggesting differential resolution of the competition among the alternatives, as reflected in the naming times. These findings characterise distinct patterns of activity associated with lexical activation and competition, supporting the theory that words are selected by competition.

Brain Oscillations and Functional Connectivity during Overt Language Production

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.

Enhancement and suppression in a lexical interference fMRI-paradigm

Previous picture-word interference (PWI) fMRI-paradigms revealed ambiguous mechanisms underlying facilitation and inhibition in healthy subjects. Lexical distractors revealed increased (enhancement) or decreased (suppression) activation in language and monitoring/control areas. Performing a secondary examination and data analysis, we aimed to illuminate the relation between behavioral and neural interference effects comparing target-related distractors (REL) with unrelated distractors (UNREL). We hypothesized that interference involves both (A) suppression due to priming and (B) enhancement due to simultaneous distractor and target processing. Comparisons to UNREL should remain distractor unspecific even at a low threshold. (C) Distractor types with common characteristics should reveal overlapping brain areas. In a 3T MRI scanner, participants were asked to name pictures while auditory words were presented (stimulus onset asynchrony [SOA] = -200 msec). Associatively and phonologically related distractors speeded responses (facilitation), while categorically related distractors slowed them down (inhibition) compared to UNREL. As a result, (A) reduced brain activations indeed resembled previously reported patterns of neural priming. Each target-related distractor yielded suppressions at least in areas associated with vision and conflict/competition monitoring (anterior cingulate cortex [ACC]), revealing least priming for inhibitors. (B) Enhancements concerned language-related but distractor-unspecific regions. (C) Some wider brain regions were commonly suppressed for combinations of distractor types. Overlapping areas associated with conceptual priming were found for facilitatory distractors (inferior frontal gyri), and areas related to phonetic/articulatory processing (precentral gyri and left parietal operculum/insula) for distractors sharing feature overlap. Each distractor with semantic relatedness revealed nonoverlapping suppressions in lexical-phonological areas (superior temporal regions). To conclude, interference combines suppression of areas well known from neural priming and enhancement of language-related areas caused by dual activation from target and distractor. Differences between interference and priming need to be taken into account. The present interference paradigm has the potential to reveal the functioning of word-processing stages, cognitive control, and responsiveness to priming at the same time.

A funny thing happened on the way to articulation: N400 attenuation despite behavioral interference in picture naming

We measured Event-Related Potentials (ERPs) and naming times to picture targets preceded by masked words (stimulus onset asynchrony: 80 ms) that shared one of three different types of relationship with the names of the pictures: (1) Identity related, in which the prime was the name of the picture ("socks" - <picture of socks>), (2) Phonemic Onset related, in which the initial segment of the prime was the same as the name of the picture ("log" - <picture of a leaf>), and (3) Semantically related in which the prime was a co-category exemplar and associated with the name of the picture ("cake" - <picture of a pie>). Each type of related picture target was contrasted with an Unrelated picture target, resulting in a 3×2 design that crossed Relationship Type between the word and the target picture (Identity, Phonemic Onset and Semantic) with Relatedness (Related and Unrelated). Modulation of the N400 component to related (versus unrelated) pictures was taken to reflect semantic processing at the interface between the picture's conceptual features and its lemma, while naming times reflected the end product of all stages of processing. Both attenuation of the N400 and shorter naming times were observed to pictures preceded by Identity related (versus Unrelated) words. No ERP effects within 600 ms, but shorter naming times, were observed to pictures preceded by Phonemic Onset related (versus Unrelated) words. An attenuated N400 (electrophysiological semantic priming) but longer naming times (behavioral semantic interference) were observed to pictures preceded by Semantically related (versus Unrelated) words. These dissociations between ERP modulation and naming times suggest that (a) phonemic onset priming occurred late, during encoding of the articulatory response, and (b) semantic behavioral interference was not driven by competition at the lemma level of representation, but rather occurred at a later stage of production.

The spatial and temporal signatures of word production components: a critical update

In the first decade of neurocognitive word production research the predominant approach was brain mapping, i.e., investigating the regional cerebral brain activation patterns correlated with word production tasks, such as picture naming and word generation. Indefrey and Levelt (2004) conducted a comprehensive meta-analysis of word production studies that used this approach and combined the resulting spatial information on neural correlates of component processes of word production with information on the time course of word production provided by behavioral and electromagnetic studies. In recent years, neurocognitive word production research has seen a major change toward a hypothesis-testing approach. This approach is characterized by the design of experimental variables modulating single component processes of word production and testing for predicted effects on spatial or temporal neurocognitive signatures of these components. This change was accompanied by the development of a broader spectrum of measurement and analysis techniques. The article reviews the findings of recent studies using the new approach. The time course assumptions of Indefrey and Levelt (2004) have largely been confirmed requiring only minor adaptations. Adaptations of the brain structure/function relationships proposed by Indefrey and Levelt (2004) include the precise role of subregions of the left inferior frontal gyrus as well as a probable, yet to date unclear role of the inferior parietal cortex in word production.

The use of electroencephalography in language production research: a review

Speech production long avoided electrophysiological experiments due to the suspicion that potential artifacts caused by muscle activity of overt speech may lead to a bad signal-to-noise ratio in the measurements. Therefore, researchers have sought to assess speech production by using indirect speech production tasks, such as tacit or implicit naming, delayed naming, or meta-linguistic tasks, such as phoneme-monitoring. Covert speech may, however, involve different processes than overt speech production. Recently, overt speech has been investigated using electroencephalography (EEG). As the number of papers published is rising steadily, this clearly indicates the increasing interest and demand for overt speech research within the field of cognitive neuroscience of language. Our main goal here is to review all currently available results of overt speech production involving EEG measurements, such as picture naming, Stroop naming, and reading aloud. We conclude that overt speech production can be successfully studied using electrophysiological measures, for instance, event-related brain potentials (ERPs). We will discuss possible relevant components in the ERP waveform of speech production and aim to address the issue of how to interpret the results of ERP research using overt speech, and whether the ERP components in language production are comparable to results from other fields.

Language production and working memory in classic galactosemia from a cognitive neuroscience perspective: future research directions

Most humans are social beings and we express our thoughts and feelings through language. In contrast to the ease with which we speak, the underlying cognitive and neural processes of language production are fairly complex and still little understood. In the hereditary metabolic disease classic galactosemia, failures in language production processes are among the most reported difficulties. It is unclear, however, what the underlying neural cause of this cognitive problem is. Modern brain imaging techniques allow us to look into the brain of a thinking patient online - while she or he is performing a task, such as speaking. We can measure indirectly neural activity related to the output side of a process (e.g. articulation). But most importantly, we can look into the planning phase prior to an overt response, hence tapping into subcomponents of speech planning. These components include verbal memory, intention to speak, and the planning of meaning, syntax, and phonology. This paper briefly introduces cognitive theories on language production and methods used in cognitive neuroscience. It reviews the possibilities of applying them in experimental paradigms to investigate language production and verbal memory in galactosemia.

ERP Evidence for Ultra-Fast Semantic Processing in the Picture-Word Interference Paradigm

We used the event-related potential (ERP) approach combined with a subtraction technique to explore the timecourse of activation of semantic and phonological representations in the picture–word interference paradigm. Subjects were exposed to to-be-named pictures superimposed on to-be-ignored semantically related, phonologically related, or unrelated words, and distinct ERP waveforms were generated time-locked to these different classes of stimuli. Difference ERP waveforms were generated in the semantic condition and in the phonological condition by subtracting ERP activity associated with unrelated picture–word stimuli from ERP activity associated with related picture–word stimuli. We measured both latency and amplitude of these difference ERP waveforms in a pre-articulatory time-window. The behavioral results showed standard interference effects in the semantic condition, and facilitatory effects in the phonological condition. The ERP results indicated a bimodal distribution of semantic effects, characterized by the extremely rapid onset (at about 100 ms) of a primary component followed by a later, distinct, component. Phonological effects in ERPs were characterized by components with later onsets and distinct scalp topography of ERP sources relative to semantic ERP components. Regression analyses revealed a covariation between semantic and phonological behavioral effect sizes and ERP component amplitudes, and no covariation between the behavioral effects and ERP component latency. The early effect of semantic distractors is thought to reflect very fast access to semantic representations from picture stimuli modulating on-going orthographic processing of distractor words.

Electrophysiological chronometry of semantic context effects in language production

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.