Sentence superiority in the reading brain.

When a sequence of written words is briefly presented and participants are asked to identify just one word at a post-cued location, then word identification accuracy is higher when the word is presented in a grammatically correct sequence compared with an ungrammatical sequence. This sentence superiority effect has been reported in several behavioral studies and two EEG investigations. Taken together, the results of these studies support the hypothesis that the sentence superiority effect is primarily driven by rapid access to a sentence-level representation via partial word identification processes that operate in parallel over several words. Here we used MEG to examine the neural structures involved in this early stage of written sentence processing, and to further specify the timing of the different processes involved. Source activities over time showed grammatical vs. ungrammatical differences first in the left inferior frontal gyrus (IFG: 321-406 ms), then the left anterior temporal lobe (ATL: 466-531 ms), and finally in both left IFG (549-602 ms) and left posterior superior temporal gyrus (pSTG: 553-622 ms). We interpret the early IFG activity as reflecting the rapid bottom-up activation of sentence-level representations, including syntax, enabled by partly parallel word processing. Subsequent activity in ATL and pSTG is thought to reflect the constraints imposed by such sentence-level representations on on-going word-based semantic activation (ATL), and the subsequent development of a more detailed sentence-level representation (pSTG). These results provide further support for a cascaded interactive-activation account of sentence reading.

Orthographic and Phonological Code Activation in Deaf and Hearing Readers.

Grainger et al. (2006) were the first to use ERP masked priming to explore the differing contributions of phonological and orthographic representations to visual word processing. Here we adapted their paradigm to examine word processing in deaf readers. We investigated whether reading-matched deaf and hearing readers (n = 36) exhibit different ERP effects associated with the activation of orthographic and phonological codes during word processing. In a visual masked priming paradigm, participants performed a go/no-go categorization task (detect an occasional animal word). Critical target words were preceded by orthographically-related (transposed letter - TL) or phonologically-related (pseudohomophone - PH) masked non-word primes were contrasted with the same target words preceded by letter substitution (control) non-words primes. Hearing readers exhibited typical N250 and N400 priming effects (greater negativity for control compared to TL or PH primed targets), and the TL and PH priming effects did not differ. For deaf readers, the N250 PH priming effect was later (250-350 ms), and they showed a reversed N250 priming effect for TL primes in this time window. The N400 TL and PH priming effects did not differ between groups. For hearing readers, those with better phonological and spelling skills showed larger early N250 PH and TL priming effects (150-250 ms). For deaf readers, those with better phonological skills showed a larger reversed TL priming effect in the late N250 window. We speculate that phonological knowledge modulates how strongly deaf readers rely on whole-word orthographic representations and/or the mapping from sublexical to lexical representations.

Different language control mechanisms in comprehension and production: Evidence from paragraph reading.

Chinese-English bilinguals read paragraphs with language switches using a rapid serial visual presentation paradigm silently while ERPs were measured (Experiment 1) or read them aloud (Experiment 2). Each paragraph was written in either Chinese or English with several function or content words switched to the other language. In Experiment 1, language switches elicited an early, long-lasting positivity when switching from the dominant language to the nondominant language, but when switching to the dominant language, the positivity started later, and was never larger than when switching to the nondominant language. In addition, switch effects on function words were not significantly larger than those on content words in any analyses. In Experiment 2, participants produced more cross-language intrusion errors when switching to the dominant than to the nondominant language, and more errors on function than content words. These results implicate different control mechanisms in bilingual language selection across comprehension and production.

Asymetric Event-Related Potential Priming Effects Between English Letters and American Sign Language Fingerspelling Fonts.

Letter recognition plays an important role in reading and follows different phases of processing, from early visual feature detection to the access of abstract letter representations. Deaf ASL-English bilinguals experience orthography in two forms: English letters and fingerspelling. However, the neurobiological nature of fingerspelling representations, and the relationship between the two orthographies, remains unexplored. We examined the temporal dynamics of single English letter and ASL fingerspelling font processing in an unmasked priming paradigm with centrally presented targets for 200 ms preceded by 100 ms primes. Event-related brain potentials were recorded while participants performed a probe detection task. Experiment 1 examined English letter-to-letter priming in deaf signers and hearing non-signers. We found that English letter recognition is similar for deaf and hearing readers, extending previous findings with hearing readers to unmasked presentations. Experiment 2 examined priming effects between English letters and ASL fingerspelling fonts in deaf signers only. We found that fingerspelling fonts primed both fingerspelling fonts and English letters, but English letters did not prime fingerspelling fonts, indicating a priming asymmetry between letters and fingerspelling fonts. We also found an N400-like priming effect when the primes were fingerspelling fonts which might reflect strategic access to the lexical names of letters. The studies suggest that deaf ASL-English bilinguals process English letters and ASL fingerspelling differently and that the two systems may have distinct neural representations. However, the fact that fingerspelling fonts can prime English letters suggests that the two orthographies may share abstract representations to some extent.

Electrophysiological patterns of visual word recognition in deaf and hearing readers: An ERP mega-study.

Deaf and hearing readers have different access to spoken phonology which may affect the representation and recognition of written words. We used ERPs to investigate how a matched sample of deaf and hearing adults (total n = 90) responded to lexical characteristics of 480 English words in a go/no-go lexical decision task. Results from mixed effect regression models showed a) visual complexity produced small effects in opposing directions for deaf and hearing readers, b) similar frequency effects, but shifted earlier for deaf readers, c) more pronounced effects of orthographic neighborhood density for hearing readers, and d) more pronounced effects of concreteness for deaf readers. We suggest hearing readers have visual word representations that are more integrated with phonological representations, leading to larger lexically-mediated effects of neighborhood density. Conversely, deaf readers weight other sources of information more heavily, leading to larger semantically-mediated effects and altered responses to low-level visual variables.

ERPs Reveal How Semantic and Syntactic Processing Unfold across Parafoveal and Foveal Vision during Sentence Comprehension.

We examined how readers process content and function words in sentence comprehension with ERPs. Participants read simple declarative sentences using a rapid serial visual presentation (RSVP) with flankers paradigm. Sentences contained either an unexpected semantically anomalous content word, an unexpected syntactically anomalous function word or were well formed with no anomalies. ERPs were examined when target words were in the parafoveal or foveal vision. Unexpected content words elicited a typically distributed N400 when displayed in the parafovea, followed by a longer-lasting, widely distributed positivity starting around 300 ms once foveated. Unexpected function words elicited a left lateralized LAN-like component when presented in the parafovea, followed by a left lateralized, posteriorly distributed P600 when foveated. These results suggested that both semantic and syntactic processing involve two stages-the initial, fast process that can be completed in parafovea, followed by a more in depth attentionally mediated assessment that occurs with direct attention.

How (and why) does iconicity effect lexical access: An electrophysiological study of American sign language.

Prior research has found that iconicity facilitates sign production in picture-naming paradigms and has effects on ERP components. These findings may be explained by two separate hypotheses: (1) a task-specific hypothesis that suggests these effects occur because visual features of the iconic sign form can map onto the visual features of the pictures, and (2) a semantic feature hypothesis that suggests that the retrieval of iconic signs results in greater semantic activation due to the robust representation of sensory-motor semantic features compared to non-iconic signs. To test these two hypotheses, iconic and non-iconic American Sign Language (ASL) signs were elicited from deaf native/early signers using a picture-naming task and an English-to-ASL translation task, while electrophysiological recordings were made. Behavioral facilitation (faster response times) and reduced negativities were observed for iconic signs (both prior to and within the N400 time window), but only in the picture-naming task. No ERP or behavioral differences were found between iconic and non-iconic signs in the translation task. This pattern of results supports the task-specific hypothesis and provides evidence that iconicity only facilitates sign production when the eliciting stimulus and the form of the sign can visually overlap (a picture-sign alignment effect).

Sensitivity to orthographic vs. phonological constraints on word recognition: An ERP study with deaf and hearing readers.

The role of phonology in word recognition has previously been investigated using a masked lexical decision task and transposed letter (TL) nonwords that were either pronounceable (barve) or unpronounceable (brvae). We used event-related potentials (ERPs) to investigate these effects in skilled deaf readers, who may be more sensitive to orthotactic than phonotactic constraints, which are conflated in English. Twenty deaf and twenty hearing adults completed a masked lexical decision task while ERPs were recorded. The groups were matched in reading skill and IQ, but deaf readers had poorer phonological ability. Deaf readers were faster and more accurate at rejecting TL nonwords than hearing readers. Neither group exhibited an effect of nonword pronounceability in RTs or accuracy. For both groups, the N250 and N400 components were modulated by lexicality (more negative for nonwords). The N250 was not modulated by nonword pronounceability, but pronounceable nonwords elicited a larger amplitude N400 than unpronounceable nonwords. Because pronounceable nonwords are more word-like, they may incite activation that is unresolved when no lexical entry is found, leading to a larger N400 amplitude. Similar N400 pronounceability effects for deaf and hearing readers, despite differences in phonological sensitivity, suggest these TL effects arise from sensitivity to lexical-level orthotactic constraints. Deaf readers may have an advantage in processing TL nonwords because of enhanced early visual attention and/or tight orthographic-to-semantic connections, bypassing the phonologically mediated route to word recognition.

On letter-specific crowding and reading: Evidence from ERPs.

We compared processing of letter and symbol stimuli presented briefly in the right or left visual field, and either in isolation or surrounded by two flanking characters of the same category. The flankers could be arranged horizontally or vertically. Participants performed a two-alternative forced choice (2AFC) task with the isolated character or the central character in flanked displays as target. Alternatives in the 2AFC task were characters from the same category as the target that were not present in the display. We recorded EEG in order to investigate the timing of crowding effects (isolated vs. flanked conditions) and the hypothesized differential impact of crowding on letters and symbols. Behavioral results showed no significant difference between isolated letters and symbols, but significantly higher accuracy to flanked letters compared with flanked symbols - and the effect of stimulus type was significantly greater with horizontally aligned stimuli. Likewise, amplitude of the N170 and a following negativity (identified here as the N250) did not differ significantly when comparing isolated letters and symbols but did differ for flanked stimuli. Flanked letters showed significantly greater N170 and N250 amplitudes compared with flanked symbols. N170 and N250 amplitudes were also significantly greater for flanked vs. isolated letters whereas symbols showed a significant difference in the opposite direction for the N250. We conclude that the processing of compact strings of letters is optimized for skilled reading via changes in the mapping of visual features onto letter identities in multi-letter arrays in order to reduce the interfering effects of excessive crowding.

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.

Are form priming effects phonological or perceptual? Electrophysiological evidence from American Sign Language.

Form priming has been used to identify and demarcate the processes that underlie word and sign recognition. The facilitation that results from the prime and target being related in form is typically interpreted in terms of pre-activation of linguistic representations, with little to no consideration for the potential contributions of increased perceptual overlap between related pairs. Indeed, isolating the contribution of perceptual similarity is impossible in spoken languages; there are no listeners who can perceive speech but have not acquired a sound-based phonological system. Here, we compared the electrophysiological indices of form priming effects in American Sign Language between hearing non-signers (i.e., who had no visual-manual phonological system) and deaf signers. We reasoned that similarities in priming effects between groups would most likely be perceptual in nature, whereas priming effects that are specific to the signer group would reflect pre-activation of phonological representations. Behavior in the go/no-go repetition detection task was remarkably similar between groups. Priming in a pre-N400 window was also largely similar across groups, consistent with an early effect of perceptual similarity. However, priming effects diverged between groups during the subsequent N400 and post-N400 windows. Signers had more typical form priming effects and were especially attuned to handshape overlap, whereas non-signers did not exhibit an N400 component and were more sensitive to location overlap. We attribute this pattern to an interplay between perceptual similarity and phonological knowledge. Perceptual similarity contributes to early phonological priming effects, while phonological knowledge tunes sensitivity to linguistically relevant dimensions of perceptual similarity.

Tracking the time course of sign recognition using ERP repetition priming.

Repetition priming and event-related potentials (ERPs) were used to investigate the time course of sign recognition in deaf users of American Sign Language. Signers performed a go/no-go semantic categorization task to rare probe signs referring to people; critical target items were repeated and unrelated signs. In Experiment 1, ERPs were time-locked either to the onset of the video or to sign onset within the video; in Experiment 2, the same full videos were clipped so that video and sign onset were aligned (removing transitional movements), and ERPs were time-locked to video/sign onset. All analyses revealed an N400 repetition priming effect (less negativity for repeated than unrelated signs) but differed in the timing and/or duration of the N400 effect. Results from Experiment 1 revealed that repetition priming effects began before sign onset within a video, suggesting that signers are sensitive to linguistic information within the transitional movement to sign onset. The timing and duration of the N400 for clipped videos were more parallel to that observed previously for auditorily presented words and was 200 ms shorter than either time-locking analysis from Experiment 1. We conclude that time-locking to full video onset is optimal when early ERP components or sensitivity to transitional movements are of interest and that time-locking to the onset of clipped videos is optimal for priming studies with fluent signers.

Matching pictures and signs: An ERP study of the effects of iconic structural alignment in American sign language.

Event-related potentials (ERPs) were used to explore the effects of iconicity and structural visual alignment between a picture-prime and a sign-target in a picture-sign matching task in American Sign Language (ASL). Half the targets were iconic signs and were presented after a) a matching visually-aligned picture (e.g., the shape and location of the hands in the sign COW align with the depiction of a cow with visible horns), b) a matching visually-nonaligned picture (e.g., the cow's horns were not clearly shown), and c) a non-matching picture (e.g., a picture of a swing instead of a cow). The other half of the targets were filler signs. Trials in the matching condition were responded to faster than those in the non-matching condition and were associated with smaller N400 amplitudes in deaf ASL signers. These effects were also observed for hearing non-signers performing the same task with spoken-English targets. Trials where the picture-prime was aligned with the sign target were responded to faster than non-aligned trials and were associated with a reduced P3 amplitude rather than a reduced N400, suggesting that picture-sign alignment facilitated the decision process, rather than lexical access. These ERP and behavioral effects of alignment were found only for the ASL signers. The results indicate that iconicity effects on sign comprehension may reflect a task-dependent strategic use of iconicity, rather than facilitation of lexical access.

Lexical selection in bimodal bilinguals: ERP evidence from picture-word interference.

The picture word interference (PWI) paradigm and ERPs were used to investigate whether lexical selection in deaf and hearing ASL-English bilinguals occurs via lexical competition or whether the response exclusion hypothesis (REH) for PWI effects is supported. The REH predicts that semantic interference should not occur for bimodal bilinguals because sign and word responses do not compete within an output buffer. Bimodal bilinguals named pictures in ASL, preceded by either a translation equivalent, semantically-related, or unrelated English written word. In both the translation and semantically-related conditions bimodal bilinguals showed facilitation effects: reduced RTs and N400 amplitudes for related compared to unrelated prime conditions. We also observed an unexpected focal left anterior positivity that was stronger in the translation condition, which we speculate may be due to articulatory priming. Overall, the results support the REH and models of bilingual language production that assume lexical selection occurs without competition between languages.

Language control in bimodal bilinguals: Evidence from ERPs.

It is currently unclear to what degree language control, which minimizes non-target language interference and increases the probability of selecting target-language words, is similar for sign-speech (bimodal) bilinguals and spoken language (unimodal) bilinguals. To further investigate the nature of language control processes in bimodal bilinguals, we conducted the first event-related potential (ERP) language switching study with hearing American Sign Language (ASL)-English bilinguals. The results showed a pattern that has not been observed in any unimodal language switching study: a switch-related positivity over anterior sites and a switch-related negativity over posterior sites during ASL production in both early and late time windows. No such pattern was found during English production. We interpret these results as evidence that bimodal bilinguals uniquely engage language control at the level of output modalities.

Orthographic neighborhood density modulates the size of transposed-letter priming effects.

We used transposed-letter (TL) priming to test the lexical tuning hypothesis, which states that words from high-density orthographic neighborhoods have more precise orthographic codes than words from low-density neighborhoods. Replicating standard TL priming effects, target words elicited faster lexical decision responses and smaller amplitude N250s and N400s when preceded by TL primes (e.g., leomn-LEMON) compared with substitution primes (e.g., leuzn-LEMON) overall. We expected that if high-density words have more precise orthographic representations (i.e., with each letter assigned to a specific position), then they should be relatively less activated by TL primes and should give rise to smaller TL priming effects. In line with our prediction, N250 (but not N400 or behavioral) TL priming was significantly smaller for high-density words compared with low-density words over posterior sites. Such an interaction was not observed for pseudoword targets. Consistent with the lexical tuning hypothesis then, this pattern suggests that the nature of the orthographic code used to access lexical representations differs depending on the number of neighboring words in the lexicon. We conclude by discussing how lexical tuning could be implemented in current models of orthographic processing.

Parallel semantic processing in the flankers task: Evidence from the N400.

The extent to which higher-order representations can be extracted from more than one word in parallel remains an unresolved issue with theoretical import. Here, we used ERPs to investigate the timing with which semantic information is extracted from parafoveal words. Participants saw animal and non-animal targets paired with response congruent or incongruent flankers in a semantic categorization task. Animal targets elicited smaller amplitude negativities when they were paired with semantically related and response congruent animal flankers (e.g., wolf coyote wolf) compared to unrelated and response incongruent flankers (e.g., sock coyote sock) in the N400 window and a post-N400 window. We interpret the N400 effect in terms of facilitated processing from the joint activation of shared semantic features (e.g., animal, furry) across target and flanker words and the later effect in terms of post-lexical decision-making. Thus, semantic information can be extracted from flankers in parallel and impacts various stages of processing.

The organization of the American Sign Language lexicon: Comparing one- and two-parameter ERP phonological priming effects across tasks.

We used phonological priming and ERPs to investigate the organization of the lexicon in American Sign Language. Across go/no-go repetition detection and semantic categorization tasks, targets in related pairs that shared handshape and location elicited smaller N400s than targets in unrelated pairs, indicative of facilitated processing. Handshape-related targets also elicited smaller N400s than unrelated targets, but only in the repetition task. The location priming effect reversed direction across tasks, with slightlylargeramplitude N400s for targets in related versus unrelated pairs in the semantic task, indicative of interference. These patterns imply that handshape and location play different roles during sign recognition and that there is a hierarchical organization for the sign lexicon. Similar to interactive-activation models of word recognition, we argue for differentiation between sublexical facilitation and lexical competition. Lexical competition is primarily driven by the location parameter and is more engaged when identification of single lexico-semantic entries is required.

Picture-naming in American Sign Language: an electrophysiological study of the effects of iconicity and structured alignment.

A picture-naming task and ERPs were used to investigate effects of iconicity and visual alignment between signs and pictures in American Sign Language (ASL). For iconic signs, half the pictures visually overlapped with phonological features of the sign (e.g., the fingers of CAT align with a picture of a cat with prominent whiskers), while half did not (whiskers are not shown). Iconic signs were produced numerically faster than non-iconic signs and were associated with larger N400 amplitudes, akin to concreteness effects. Pictures aligned with iconic signs were named faster than non-aligned pictures, and there was a reduction in N400 amplitude. No behavioral effects were observed for the control group (English speakers). We conclude that sensory-motoric semantic features are represented more robustly for iconic than non-iconic signs (eliciting a concreteness-like N400 effect) and visual overlap between pictures and the phonological form of iconic signs facilitates lexical retrieval (eliciting a reduced N400).

Masked ERP repetition priming in deaf and hearing readers.

Deaf readers provide unique insights into how the reading circuit is modified by altered linguistic and sensory input. We investigated whether reading-matched deaf and hearing readers (n = 62) exhibit different ERP effects associated with orthographic to phonological mapping (N250) or lexico-semantic processes (N400). In a visual masked priming paradigm, participants performed a go/no-go categorization task; target words were preceded by repeated or unrelated primes. Prime duration and word frequency were manipulated. Hearing readers exhibited typical N250 and N400 priming effects with 50 ms primes (greater negativity for unrelated primes) and smaller effects with 100 ms primes. Deaf readers showed a surprising reversed priming effect with 50 ms primes (greater negativity for related primes), and more typical N250 and N400 effects with 100 ms primes. Correlation results suggested deaf readers with poorer phonological skills drove this effect. We suggest that weak phonological activation may create orthographic "repetition enhancement" or form/lexical competition in deaf readers.