Embedded word priming elicits enhanced fMRI responses in the visual word form area.

Lexical embedding is common in all languages and elicits mutual orthographic interference between an embedded word and its carrier. The neural basis of such interference remains unknown. We employed a novel fMRI prime-target embedded word paradigm to test for involvement of a visual word form area (VWFA) in left ventral occipitotemporal cortex in co-activation of embedded words and their carriers. Based on the results of related fMRI studies we predicted either enhancement or suppression of fMRI responses to embedded words initially viewed as primes, and repeated in the context of target carrier words. Our results clearly showed enhancement of fMRI responses in the VWFA to embedded-carrier word pairs as compared to unrelated prime-target pairs. In contrast to non-visual language-related areas (e.g., left inferior frontal gyrus), enhanced fMRI responses did not occur in the VWFA when embedded-carrier word pairs were restricted to the left visual hemifield. Our finding of fMRI enhancement in the VWFA is novel evidence of its involvement in representational rivalry between orthographically similar words, and the co-activation of embedded words and their carriers.

No deficiency in left-to-right processing of words in dyslexia but evidence for enhanced visual crowding.

Whitney and Cornelissen hypothesized that dyslexia may be the result of problems with the left-to-right processing of words, particularly in the part of the word between the word beginning and the reader's fixation position. To test this hypothesis, we tachistoscopically presented consonant trigrams in the left and the right visual field (LVF, RVF) to 20 undergraduate students with dyslexia and 20 matched controls. The trigrams were presented at different locations (from -2.5° to + 2.5°) in both visual half fields. Participants were asked to identify the letters, and accuracy rates were compared. In line with the predictions of the SERIOL (sequential encoding regulated by inputs to oscillations within letter units) model of visual word recognition, a typical U-shaped pattern was found at all retinal locations. Accuracy also decreased the further away the stimulus was from the fixation location, with a steeper decrease in the LVF than in the RVF. Contrary to the hypothesis, the students with dyslexia showed the same pattern of results as did the control participants, also in the LVF, apart from a slightly lower accuracy rate, particularly for the central letter. The latter is in line with the possibility of enhanced crowding in dyslexia. In addition, in the dyslexia group but not in the control group the degree of crowding correlated significantly with the students' word reading scores. These findings suggest that lateral inhibition between letters is associated with word reading performance in students with dyslexia.

The study of orthographic processing has broadened research in visual word recognition.

Interest in orthographic processing reflects an expansion, not constriction, of the scope of research in visual word recognition (VWR). Transposition effects are merely one aspect of investigations into orthographic encoding, while open bigrams can accommodate differences across languages. The target article's inaccurate characterization of the study of orthographic processing is not conducive to the advancement of VWR research.

On coding the position of letters in words: a test of two models.

Open-bigram and spatial-coding schemes provide different accounts of how letter position is encoded by the brain during visual word recognition. Open-bigram coding involves an explicit representation of order based on letter pairs, while spatial coding involves a comparison function operating over representations of individual letters. We identify a set of priming conditions (subset primes and reversed interior primes) for which the two types of coding schemes give opposing predictions, hence providing the opportunity for strong scientific inference. Experimental results are consistent with the open-bigram account, and inconsistent with the spatial-coding scheme.

Location, location, location: how it affects the neighborhood (effect).

Reaction times in lexical decision are more sensitive to a words' length and orthographic-neighborhood density when the stimulus is presented to the left visual field (LVF) than to the right visual field (RVF). We claim that the length effect is equivalent to the neighborhood effect, and propose a novel explanation of why the LVF, but not the RVF, is sensitive to density, based on different firing rates of abstract-letter representations encoding letters falling in the LVF versus RVF. We support this proposal with a large-scale implemented model of lexical decision utilizing spiking units, which provides a reasonable fit to the data from the English Lexicon Project under simulated central presentation, while replicating the observed hemifield asymmetries under simulated lateralized presentation.

Activation of the left inferior frontal gyrus in the first 200 ms of reading: evidence from magnetoencephalography (MEG).

BACKGROUND: It is well established that the left inferior frontal gyrus plays a key role in the cerebral cortical network that supports reading and visual word recognition. Less clear is when in time this contribution begins. We used magnetoencephalography (MEG), which has both good spatial and excellent temporal resolution, to address this question. METHODOLOGY/PRINCIPAL FINDINGS: MEG data were recorded during a passive viewing paradigm, chosen to emphasize the stimulus-driven component of the cortical response, in which right-handed participants were presented words, consonant strings, and unfamiliar faces to central vision. Time-frequency analyses showed a left-lateralized inferior frontal gyrus (pars opercularis) response to words between 100-250 ms in the beta frequency band that was significantly stronger than the response to consonant strings or faces. The left inferior frontal gyrus response to words peaked at approximately 130 ms. This response was significantly later in time than the left middle occipital gyrus, which peaked at approximately 115 ms, but not significantly different from the peak response in the left mid fusiform gyrus, which peaked at approximately 140 ms, at a location coincident with the fMRI-defined visual word form area (VWFA). Significant responses were also detected to words in other parts of the reading network, including the anterior middle temporal gyrus, the left posterior middle temporal gyrus, the angular and supramarginal gyri, and the left superior temporal gyrus. CONCLUSIONS/SIGNIFICANCE: These findings suggest very early interactions between the vision and language domains during visual word recognition, with speech motor areas being activated at the same time as the orthographic word-form is being resolved within the fusiform gyrus. This challenges the conventional view of a temporally serial processing sequence for visual word recognition in which letter forms are initially decoded, interact with their phonological and semantic representations, and only then gain access to a speech code.

Comparison of the SERIOL and SOLAR theories of letter-position encoding.

There has been increasing interest in the question of how the brain encodes the order of letters in a written word. This problem is of practical and theoretical interest, so it is important to distinguish between competing computational models. This article compares the SERIOL and SOLAR theories on their biological plausibility and ability to explain experimental results at the orthographic and lexical levels.

Evaluation of synthetic oligonucleotides as inhibitors of West Nile virus replication.

A series of synthetic oligonucleotide phosphorothioate 15-mers were generated against specific sequences in the West Nile virus RNA genome. These antisense oligonucleotides targeted (1) conserved features of the West Nile virus RNA genome that may be expected to lead to inhibition of virus replication since such features play essential roles in the virus lifecycle; (2) G-quartet oligonucleotides with potential facilitated uptake properties and that also targeted conserved sequences among a range of West Nile virus strains. Several formulations with significant in vitro antiviral activity were found. Among the active oligonucleotides were examples that targeted both C-rich RNA sequences of the West Nile RNA genome as well as recognized conserved sequences key to West Nile virus replication. Since the antiviral activity of the latter oligonucleotides diminished upon 2'-O-methyl substitution, it is likely that their activity involves RNase H-catalyzed RNA degradation. One G-rich oligonucleotide that did not target a West Nile virus RNA sequence also was found. These results suggest the potential of antisense strategies for the control of West Nile virus replication if the attendant problem of oligonucleotide delivery can be adequately addressed.

Facilitative orthographic neighborhood effects: the SERIOL model account.

A large orthographic neighborhood (N) facilitates lexical decision for central and left visual field/right hemisphere (LVF/RH) presentation, but not for right visual field/left hemisphere (RVF/LH) presentation. Based on the SERIOL model of letter-position encoding, this asymmetric N effect is explained by differential activation patterns at the orthographic level. This analysis implies that it should be possible to negate the LVF/RH N effect and create an RVF/LH N effect by manipulating contrast levels in specific ways. In Experiment 1, these predictions were confirmed. In Experiment 2, we eliminated the N effect for both LVF/RH and central presentation. These results indicate that the letter level is the primary locus of the N effect under lexical decision, and that the hemispheric specificity of the N effect does not reflect differential processing at the lexical level.

Word length effects in Hebrew.

Numerous lateralization studies have reported that word length has a stronger effect in the left visual field (LVF) than in the right visual field (RVF) for right-handed people due to hemispheric asymmetry for language processing. Alternatively, early perceptual learning theory argued that the length effects might depend on the frequency of having read words at various lengths displayed at different retinal locations. The two alternatives were tested with right-handers participants who were native speakers of Hebrew which is read from right to left, that is Hebrew readers have a different perceptual experience than English readers. We found the predicted interaction between word length and hemifield; however, longer latencies to longer letter strings were found at both visual fields. We argue that these results are best accounted by the SERIOL model of letter-position encoding.

Why word length only matters in the left visual field.

During visual word recognition, string length affects performance when stimuli are presented to the left visual field (LVF), but not when they are presented to the right visual field (RVF). Using a lexical-decision experiment, we investigated an account of this phenomenon based on the SERIOL model of letter-position encoding. Bottom-up activation patterns were adjusted via positional manipulations of letter contrast. This manipulation eliminated the LVF length effect by facilitating responses to longer words, thereby demonstrating that a length effect is not an inherent property of right-hemisphere processing. In contrast, the same manipulation slowed responses to longer words in the RVF, creating a length effect. These results show that hemisphere-specific activation patterns are the source of the asymmetry of the length effect.