Manuel Carreiras

An anatomical signature for literacy

Language is a uniquely human ability that evolved at some point in the roughly 6,000,000 years since human and chimpanzee lines diverged. Even in the most linguistically impoverished environments, children naturally develop sophisticated language systems. In contrast, reading is a learnt skill that does not develop without intensive tuition and practice. Learning to read is likely to involve ontogenic structural brain changes, but these are nearly impossible to isolate in children owing to concurrent biological, environmental and social maturational changes. In Colombia, guerrillas are re-integrating into mainstream society and learning to read for the first time as adults. This presents a unique opportunity to investigate how literacy changes the brain, without the maturational complications present in children. Here we compare structural brain scans from those who learnt to read as adults (late-literates) with those from a carefully matched set of illiterates. Late-literates had more white matter in the splenium of the corpus callosum and more grey matter in bilateral angular, dorsal occipital, middle temporal, left supramarginal and superior temporal gyri. The importance of these brain regions for skilled reading was investigated in early literates, who learnt to read as children. We found anatomical connections linking the left and right angular and dorsal occipital gyri through the area of the corpus callosum where white matter was higher in late-literates than in illiterates; that reading, relative to object naming, increased the interhemispheric functional connectivity between the left and right angular gyri; and that activation in the left angular gyrus exerts top-down modulation on information flow from the left dorsal occipital gyrus to the left supramarginal gyrus. These findings demonstrate how the regions identified in late-literates interact during reading, relative to object naming, in early literates.

Effects of orthographic neighborhood in visual word recognition : Cross-task comparisons

Effects of orthographic neighborhood in visual word recognition in Spanish were examined in 5 paradigms: progressive demasking, standard lexical decision, lexical decision with blocking of neighborhood density, naming, and semantic categorization. The results showed inhibitory effects of neighborhood frequency in the progressive-demasking task, in both lexical-decision tasks, as well as for low-density words in the naming task, and for high-density words in the semantic-categorization task. Higher levels of neighborhood density produced an inhibitory trend in the progressive-demasking task, facilitation in lexical decision (significant only when neighborhood density was blocked), and a robust facilitation effect in naming (only for words with higher frequency neighbors). A global analysis across tasks and one simulation study helped outline some of the underlying task-specific and task-independent mechanisms.

Grammatical Gender and Number Agreement in Spanish: An ERP Comparison

The role of grammatical gender and number representations in syntactic processes during reading in Spanish was studied using the event-related potentials (ERPs) technique. The electroencephalogram was recorded with a dense array of 128 electrodes while Spanish speakers read word pairs (Experiment 1) or sentences (Experiment 2) in which gender or number agreement relationships were manipulated. Disagreement in word pairs formed by a noun and an adjective (e.g., faroalto [lighthousehigh]) produced an N400-type effect, while word pairs formed by an article and a noun (e.g., elpiano [the-piano]) showed an additional left anterior negativity effect (LAN). Agreement violations with the same words inserted in sentences (e.g., El piano estaba viejo y desafinado [the m-s piano m-s was old m-s and off-key]) resulted in a pattern of LANP600. This effect was found both when the violation occurred in the middle of the sentence (at the adjective), as well as when this happened at the beginning of the sentence (at the noun), but the last segment of the P600 effect was greater for the middle sentence position, which could indicate differences in the complexity of reanalysis processes. Differences between grammatical gender and number disagreement were found in late measures. In the word pairs experiment, P3 peak latency varied across conditions, being later for gender than for number disagreement. Similarly, in the sentence experiment, the last segment of the P600 effect was greater for gender than for number violations. These event-related potentials (ERPs) effects lend support to the idea that reanalysis or repair processes after grammatical disagreement detection could involve more steps in the case of gender disagreement, as grammatical gender is a feature of the lexical representation in contrast to number, which is considered a morphological feature that combines with the stem of the word.

Effects of syllable frequency and syllable neighborhood frequency in visual word recognition.

Three experiments were carried out to analyze the role of syllable frequency in lexical decision and naming. The results show inhibitory effects of syllable frequency in the lexical decision task for both high- and low-frequency words. In contrast, the effect of syllable frequency is facilitatory in the naming task. A post hoc analysis revealed the important role played by the number of higher frequency syllabic neighbors (words that share a syllable with the target) in the lexical decision task and the role of the frequency of the first syllable in the naming task. Experiment 3 manipulated the neighborhood syllable frequency directly by comparing words with few higher frequency syllabic neighbors and words with many higher frequency syllabic neighbors in the lexical decision task; an inhibitory neighborhood syllable frequency effect was found. The results are interpreted in terms of current models of visual word recognition and word naming.

Grammatical agreement processing in reading: ERP findings and future directions.

In the domain of written sentence comprehension, the computation of agreement dependencies is generally considered as a form-driven processing routine whose domain is syntactic in nature. In the present review we discuss the main findings emerging in the Event-Related Potential (ERP) literature on sentence comprehension, focusing on the different dimensions of agreement patterns (features, values, constituents involved and language): Agreement mismatches usually evoke a biphasic electrophysiological pattern (Left Anterior Negativity - LAN, 300-450 msec and P600 after 500 msec). This ERP pattern is assumed to reflect rule-based computations sensitive to formal (inflectional) covariations of related words (trigger-target). Here we claim that agreement processing is sensitive to both the type of feature involved and the constituents that express the agreement dependency. More specifically, LAN could reflect violation of expectancy (elicited by the trigger) for the target functional morphology; later, trigger and target are structurally integrated at the sentence level (early P600). However, morphosyntactic information could trigger the activation of higher-level representations that are not strictly syntactic in nature. The recruitment of this additional non-syntactic information (mirrored by N400-like effects) indicates that rule-based computations of agreement dependencies are not blind to non-syntactic information but are often recruited to establish sentence-level relations.

Syllable-frequency effects in visual word recognition: evidence from ERPs.

A lexical decision experiment was conducted while event related potentials (ERPs) were recorded. The word frequency and the first syllable frequency of each word were manipulated. Results showed that, while high frequency words produced less negative amplitudes in the N400 time window than low frequency words, the inverse pattern was found for syllable frequency. Words containing high frequency syllables produced more negative amplitudes than words containing low frequency syllables. Importantly, a significant syllable frequency effect was also obtained at the P200 time window. The results are interpreted in the framework of an interactive activation model, in which high frequency syllables produce the initial activation of a larger number of lexical candidates during the analysis of orthographic or phonological representations, which have to be inhibited later to allow the identification of a unique word. These findings support the idea that, at least in languages with clear syllabic boundaries, syllables are functional sublexical units during visual word recognition.

Morphosyntactic processing in late second-language learners

The goal of the present study was to investigate the electrophysiological correlates of second-language (L2) morphosyntactic processing in highly proficient late learners of an L2 with long exposure to the L2 environment. ERPs were collected from 22 English–Spanish late learners while they read sentences in which morphosyntactic features of the L2 present or not present in the first language (number and gender agreement, respectively) were manipulated at two different sentence positions—within and across phrases. The results for a control group of age-matched native-speaker Spanish participants included an ERP pattern of LAN-type early negativity followed by P600 effect in response to both agreement violations and for both sentence positions. The late L2 learner results included a similar pattern, consisting of early negativity followed by P600, in the first sentence position (within-phrase agreement violations) but only P600 effects in the second sentence position (across-phrase agreement violation), as well as significant amplitude and onset latency differences between the gender and the number violation effects in both sentence positions. These results reveal that highly proficient learners can show electrophysiological correlates during L2 processing that are qualitatively similar to those of native speakers, but the results also indicate the contribution of factors such as age of acquisition and transfer processes from first language to L2.

EsPal: One-stop shopping for Spanish word properties

This article introduces EsPal: a Web-accessible repository containing a comprehensive set of properties of Spanish words. EsPal is based on an extensible set of data sources, beginning with a 300 million token written database and a 460 million token subtitle database. Properties available include word frequency, orthographic structure and neighborhoods, phonological structure and neighborhoods, and subjective ratings such as imageability. Subword structure properties are also available in terms of bigrams and trigrams, biphones, and bisyllables. Lemma and part-of-speech information and their corresponding frequencies are also indexed. The website enables users either to upload a set of words to receive their properties or to receive a set of words matching constraints on the properties. The properties themselves are easily extensible and will be added over time as they become available. It is freely available from the following website: http://www.bcbl.eu/databases/espal/.

Syllables and morphemes: contrasting frequency effects in Spanish.

Three types of sublexical units were studied in Spanish visual word recognition: the syllable, the basic orthographic syllabic structure (BOSS), and the root morpheme. In Experiment 1, using a lexical-decision task, a typical inhibitory effect of the first-syllable frequency was found (while keeping constant the BOSS frequency) as well as the word-frequency effect. Experiment 2 examined the role of both the BOSS frequency and the word frequency, also in a lexical-decision task. Syllable frequency was controlled. Both the BOSS frequency and the word frequency showed facilitatory effects. However, in Experiments 3A and 3B, a facilitatory effect of the root frequency (when controlling for BOSS frequency) and a null effect of BOSS frequency (when controlling for root frequency) were found, suggesting that the BOSS effect is in fact reflecting a morpheme effect. A review of the current models shows that it is difficult to integrate syllables and morphemes in a unique model.

Effect of word and syllable frequency on activation during lexical decision and reading aloud.

This functional MRI (fMRI) study investigated the effect of lexical and syllable frequency on visual word processing during lexical decision and reading aloud. Previous research has shown a dissociation of syllable and word frequency effects in Spanish using behavioral and electrophysiological measures, suggesting that sublexical (syllabic) representations are computed and mediate the firing of lexical candidates. Here, we characterize the neuroanatomical basis of these lexical and sublexical manipulations and their dependence on task. During lexical decision, words with low vs. high lexical frequency increased activation in left frontal, anterior cingulate, supplemental motor area (SMA), and pre‐SMA regions; while words with high vs. low syllable frequency increased activation in a left anterior inferior temporal region. In contrast, when the words were read aloud those with low vs. high syllable frequency increased activation in the left anterior insula, with no other significant effects. On the basis of the neuroanatomy, we propose that the contrasting effects of syllable frequency during lexical decision and reading aloud reflect two different cognitive processes in visual word processing. Specifically, words with high‐frequency syllables may increase lexical competition in the inferior temporal lobe while facilitating articulatory planning in the left anterior insula. Hum Brain Mapp, 2006.