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.

BDNF as potential biomarker of epilepsy severity and psychiatric comorbidity: pitfalls in the clinical population.

BACKGROUND: Several studies implicate brain-derived neurotrophic factor (BDNF) in the pathophysiology of epilepsy. In particular, preclinical data suggest that lower serum BDNF is a biomarker of epilepsy severity and psychiatric comorbidities. We tested this prediction in clinical epilepsy cohorts. METHODS: Patients with epilepsy were recruited from 4 epilepsy centers in France and serum BDNF was quantified. Clinical characteristics including epilepsy duration, classification, localization, etiology, seizure frequency and drug resistance were documented. Presence of individual anti-seizure medications (ASM) was noted. Screening for depression and anxiety symptoms was carried out in all patients using the NDDI-E and the GAD-7 scales. In patients with positive screening for anxiety and/or depression, detailed psychiatric testing was performed including the Mini International Neuropsychiatric Interview (MINI), STAI-Y, Holmes Rahe Stressful Events Scale and Beck Depression Interview. Descriptive analysis was applied. Spearman's test and Pearson's co-efficient were used to assess the association between BDNF level and continuous variables. For discrete variables, comparison of means (Student's t-test, Mann-Whitney u-test) was used to compare mean BDNF serum level between groups. Multivariate analysis was performed using a regression model. RESULTS: No significant correlation was found between serum BDNF level and clinical features of epilepsy or measures of depression. The main group-level finding was that presence of any ASM at was associated with increased BDNF; this effect was particularly significant for valproate and perampanel. CONCLUSION: Presence of ASM affects serum BDNF levels in patients with epilepsy. Future studies exploring BDNF as a possible biomarker of epilepsy severity and/or psychiatric comorbidity must control for ASM effects.

Multi-LEX: A database of multi-word frequencies for French and English.

Written word frequency is a key variable used in many psycholinguistic studies and is central in explaining visual word recognition. Indeed, methodological advances on single-word frequency estimates have helped to uncover novel language-related cognitive processes, fostering new ideas and studies. In an attempt to support and promote research on a related emerging topic, visual multi-word recognition, we extracted from the exhaustive Google Ngram datasets a selection of millions of multi-word sequences and computed their associated frequency estimate. Such sequences are presented with part-of-speech information for each individual word. An online behavioral investigation making use of the French 4-gram lexicon in a grammatical decision task was carried out. The results show an item-level frequency effect of word sequences. Moreover, the proposed datasets were found useful during the stimulus selection phase, allowing more precise control of the multi-word characteristics.

On the relations between letter, word, and sentence-level processing during reading.

Much prior research on reading has focused on a specific level of processing, with this often being letters, words, or sentences. Here, for the first time in adult readers, we provide a combined investigation of these three key component processes of reading comprehension. We did so by testing the same group of participants in three tasks thought to reflect processing at each of these levels: alphabetic decision, lexical decision, and grammatical decision. Participants also performed a non-reading classification task, with an aim to partial-out common binary decision processes from the correlations across the three main tasks. We examined the pairwise partial correlations for response times (RTs) in the three reading tasks. The results revealed strong significant correlations across adjacent levels of processing (i.e., letter-word; word-sentence) and a non-significant correlation between non-adjacent levels (letter-sentence). The results provide an important new benchmark for evaluating computational models that describe how letters, words, and sentences contribute to reading comprehension.

Letter and word identification in the fovea and parafovea.

We investigated the extent to which accuracy in word identification in foveal and parafoveal vision is determined by variations in the visibility of the component letters of words. To do so we measured word identification accuracy in displays of three three-letter words, one on fixation and the others to the left and right of the central word. We also measured accuracy in identifying the component letters of these words when presented at the same location in a context of three three-letter nonword sequences. In the word identification block, accuracy was highest for central targets and significantly greater for words to the right compared with words to the left. In the letter identification block, we found an extended W-shaped function across all nine letters, with greatest accuracy for the three central letters and for the first and last letter in the complete sequence. Further analyses revealed significant correlations between average letter identification per nonword position and word identification at the corresponding position. We conclude that letters are processed in parallel across a sequence of three three-letter words, hence enabling parallel word identification when letter identification accuracy is high enough.

An ERP investigation of transposed-word effects in same-different matching.

Can several words be read in parallel, and if so, how is information about word order encoded under such circumstances? Here we focused on the bottom-up mechanisms involved in word-order encoding under the hypothesis of parallel word processing. We recorded EEG while participants performed a visual same-different matching task with sequences of five words (reference sequence followed by a target sequence each presented for 400 ms). The reference sequence could be grammatically correct or an ungrammatical scrambling of the same words (e.g., he wants these green apples/green wants these he apples). Target sequences for 'different' responses were created by either transposing two words in the reference (e.g., he these wants green apples/green these wants he apples), or by changing two words (e.g., he talks their green apples/green talks their he apples). Different responses were harder to make in the transposition condition, and this transposed-word effect started to emerge around 250 ms post-target onset. The transposed-word effect was first seen on an early onsetting N400 component, with reduced amplitudes (i.e., less negative ERPs) in the transposed condition relative to a two-word replacement condition. A later transposed-word effect was seen on a more temporally widespread positive-going component. Converging behavioral and EEG results showed no effects of reference grammaticality on 'different' responses nor an interaction with transposed-word effects. Our results point to the noisy, bottom-up association of word identities to spatiotopic locations as one means of encoding word order information, and one key source of transposed-word effects.

Parafoveal-on-foveal repetition effects in sentence reading: A co-registered eye-tracking and electroencephalogram study.

When reading, can the next word in the sentence (word n + 1) influence how you read the word you are currently looking at (word n)? Serial models of sentence reading state that this generally should not be the case, whereas parallel models predict that this should be the case. Here we focus on perhaps the simplest and the strongest Parafoveal-on-Foveal (PoF) manipulation: word n + 1 is either the same as word n or a different word. Participants read sentences for comprehension and when their eyes left word n, the repeated or unrelated word at position n + 1 was swapped for a word that provided a syntactically correct continuation of the sentence. We recorded electroencephalogram and eye-movements, and time-locked the analysis of fixation-related potentials (FRPs) to fixation of word n. We found robust PoF repetition effects on gaze durations on word n, and also on the initial landing position on word n. Most important is that we also observed significant effects in FRPs, reaching significance at 260 ms post-fixation of word n. Repetition of the target word n at position n + 1 caused a widely distributed reduced negativity in the FRPs. Given the timing of this effect, we argue that it is driven by orthographic processing of word n + 1, while readers were still looking at word n, plus the spatial integration of orthographic information extracted from these two words in parallel.

Stimulus orientation and the first-letter advantage.

A post-cued partial report target-in-string identification experiment examined the influence of stimulus orientation on the serial position functions for strings of five consonants or five symbols, with an aim to test different accounts of the first-letter advantage observed in prior research. Under one account, this phenomenon is driven by processing that is specific to horizontally arranged letter (and digit) strings. An alternative account explains the first-letter advantage in terms of attentional biases towards the beginning of letter strings. We observed a significant three-way interaction between stimulus type (letters vs. symbols), serial position (1-5), and orientation (horizontal vs. vertical) that was driven by a greater first-position advantage for letters than symbols when stimuli were presented horizontally compared with vertical presentation. These results provide support for the letter-specific processing account of the first-letter advantage, and further suggest that differences in visual complexity between letters and symbols play a minor role. Nevertheless, a first-position advantage for letters was observed in the vertical presentation condition, thus pointing to some role for attentional biases that operate independently of string orientation.

MEGALEX: A megastudy of visual and auditory word recognition.

Using the megastudy approach, we report a new database (MEGALEX) of visual and auditory lexical decision times and accuracy rates for tens of thousands of words. We collected visual lexical decision data for 28,466 French words and the same number of pseudowords, and auditory lexical decision data for 17,876 French words and the same number of pseudowords (synthesized tokens were used for the auditory modality). This constitutes the first large-scale database for auditory lexical decision, and the first database to enable a direct comparison of word recognition in different modalities. Different regression analyses were conducted to illustrate potential ways to exploit this megastudy database. First, we compared the proportions of variance accounted for by five word frequency measures. Second, we conducted item-level regression analyses to examine the relative importance of the lexical variables influencing performance in the different modalities (visual and auditory). Finally, we compared the similarities and differences between the two modalities. All data are freely available on our website ( https://sedufau.shinyapps.io/megalex/ ) and are searchable at www.lexique.org , inside the Open Lexique search engine.

A Vision of Reading.

Different fields of research within the cognitive sciences have investigated basic processes in reading, but progress has been hampered by limited cross-fertilization. We propose a theoretical framework aimed at facilitating integration of findings obtained via these different approaches with respect to the impact of visual factors on reading. We describe a specialized system for parallel letter processing that assigns letter identities to different locations along the horizontal meridian within the limits imposed by visual acuity and crowding. Spatial attention is used to set up this system during reading development, and difficulty in doing so has repercussions in terms of efficient translation of the orthographic code into its phonological counterpart, and fast access to semantics from print.

A Thousand Words Are Worth a Picture: Snapshots of Printed-Word Processing in an Event-Related Potential Megastudy.

In the experiment reported here, approximately 1,000 words were presented to 75 participants in a go/no-go lexical decision task while event-related potentials (ERPs) were recorded. Partial correlations were computed for variables selected to reflect orthographic, lexical, and semantic processing, as well as for a novel measure of the visual complexity of written words. Correlations were based on the item-level ERPs at each electrode site and time slice while a false-discovery-rate correction was applied. Early effects of visual complexity were seen around 50 ms after word onset, followed by the earliest sustained orthographic effects around 100 to 150 ms, with the bulk of orthographic and lexical influences arising after 200 ms. Effects of a semantic variable (concreteness) emerged later, at around 300 ms. The overall time course of these ERP effects is in line with hierarchical, cascaded, interactive accounts of word recognition, in which fast feed-forward influences are consolidated by top-down feedback via recurrent processing loops.

Strategy combination in human cognition: a behavioral and ERP study in arithmetic.

It is well known that people use several strategies to accomplish most cognitive tasks. Unknown is whether they can combine two strategies. The present study found that such strategy combination can occur and improves participants' performance. Participants verified complex multiplication problems that violated the five rule (5 × 32 = 164), parity rule (5 × 12 = 65), both parity and five rules (5 × 31 = 158), or no rule (5 × 26 = 140). Participants obtained better performance on problems violating both five and parity rules than on problems violating either (or no) rule. Moreover, we found event-related potential (ERP) differences between two-rule and one-rule violation problems between 550 ms and 850 ms post-stimulus presentation, and ERP differences between parity-rule and five-rule violation problems between 850 ms and 1,400 ms. These findings have important implications to further our understanding of strategic variations in human cognition and suggest that strategy combination may occur in a wide variety of cognitive domains.

Sequential modulations of poorer-strategy effects during strategy execution: an event-related potential study in arithmetic.

When participants accomplish cognitive tasks, they obtain poorer performance if asked to execute a poorer strategy than a better strategy on a given problem. These poorer-strategy effects are smaller following execution of a poorer strategy relative to following a better strategy. To investigate ERP correlates of sequential modulations of poorer-strategy effects, we asked participants (n=20) to accomplish a computational estimation task (i.e., provide approximate products to two-digit multiplication problems like 38×74). For each problem, they were cued to execute a better versus a poorer strategy. We found event-related potentials signatures of sequential modulations of poorer-strategy effects in two crucial windows (i.e., between 200 and 550 ms and between 850 and 1250 ms) associated with executive control mechanisms and allowing conflict monitoring between the better and the cued strategy. These results have important implications on theories of strategies as they suggest that sequential modulations of poorer-strategy effects involve earlier as well as later mechanisms of cognitive control during strategy execution.

Deep learning of orthographic representations in baboons.

What is the origin of our ability to learn orthographic knowledge? We use deep convolutional networks to emulate the primate's ventral visual stream and explore the recent finding that baboons can be trained to discriminate English words from nonwords. The networks were exposed to the exact same sequence of stimuli and reinforcement signals as the baboons in the experiment, and learned to map real visual inputs (pixels) of letter strings onto binary word/nonword responses. We show that the networks' highest levels of representations were indeed sensitive to letter combinations as postulated in our previous research. The model also captured the key empirical findings, such as generalization to novel words, along with some intriguing inter-individual differences. The present work shows the merits of deep learning networks that can simulate the whole processing chain all the way from the visual input to the response while allowing researchers to analyze the complex representations that emerge during the learning process.

The time course of strategy sequential difficulty effects: an ERP study in arithmetic.

Uittenhove and Lemaire (Exp Psychol 59(5):295-301, 2012) found that we are slower when executing a strategy following a difficult strategy than when executing the same strategy following an easier strategy (i.e., strategy sequential difficulty effects). Uittenhove and Lemaire suggested that difficult strategies temporarily reduce available executive capacities, interfering with the next strategy execution. In this study, we used ERP to determine the time course of these effects. In a computational estimation task, we found greater cerebral activities during strategy execution following a more difficult compared to an easier strategy. Interestingly, greater cerebral activities were most apparent immediately after the encoding of the problem and not during encoding or in later stages of processing. This suggests that strategy sequential difficulty effects interfere most with the retrieval of procedures in contrast to execution of these procedures. We discuss implications of these findings for further understanding of execution of cognitive strategies.

How to say "no" to a nonword: a leaky competing accumulator model of lexical decision.

We describe a leaky competing accumulator (LCA) model of the lexical decision task that can be used as a response/decision module for any computational model of word recognition. The LCA model uses evidence for a word, operationalized as some measure of lexical activity, as input to the YES decision node. Input to the NO decision node is simply a constant value minus evidence for a word. In this way, evidence for a nonword is a function of time from stimulus onset (as in standard deadline models) modulated by lexical activity via the competitive dynamics of the LCA. We propose a simple mechanism for determining the value of this constant online during the first trials of a lexical decision experiment, such that the model can rapidly optimize speed and accuracy in discriminating words from nonwords. Further optimization is achieved via trial-by-trial adjustments in response criteria as a function of task demands and list context. We show that the LCA model can simulate mean response times and response distributions for correct and incorrect YES and NO decisions for a number of benchmark experiments that have been shown to be fatal for deadline models of lexical decision. Finally, using lexical activity calculated by a computational model of word recognition as input to the LCA decision module, we provide the first item-level simulation of both word and nonword responses in a large-scale database.

The "electrophysiological sandwich": a method for amplifying ERP priming effects.

We describe the results of a study that combines ERP recordings and sandwich priming, a variant of masked priming that provides a brief preview of the target prior to prime presentation (S. J. Lupker & C. J. Davis, 2009). This has been shown to increase the size of masked priming effects seen in behavioral responses. We found the same increase in sensitivity to ERP priming effects in an orthographic priming experiment manipulating the position of overlap of letters shared by primes and targets. Targets were 6-letter words and primes were formed of the 1st, 3rd, 4th, and 6th letters of targets in the related condition. Primes could be concatenated or hyphenated and could be centered on fixation or displaced by two letter spaces to the left or right. Priming effects with concatenated and/or displaced primes only started to emerge at 250 ms post-target onset, whereas priming effects from centrally located hyphenated primes emerged about 100 ms earlier.