Hybrid Genetic Algorithm for Clustering IC Topographies of EEGs.

Clustering of independent component (IC) topographies of Electroencephalograms (EEG) is an effective way to find brain-generated IC processes associated with a population of interest, particularly for those cases where event-related potential features are not available. This paper proposes a novel algorithm for the clustering of these IC topographies and compares its results with the most currently used clustering algorithms. In this study, 32-electrode EEG signals were recorded at a sampling rate of 500 Hz for 48 participants. EEG signals were pre-processed and IC topographies computed using the AMICA algorithm. The algorithm implements a hybrid approach where genetic algorithms are used to compute more accurate versions of the centroids and the final clusters after a pre-clustering phase based on spectral clustering. The algorithm automatically selects the optimum number of clusters by using a fitness function that involves local-density along with compactness and separation criteria. Specific internal validation metrics adapted to the use of the absolute correlation coefficient as the similarity measure are defined for the benchmarking process. Assessed results across different ICA decompositions and groups of subjects show that the proposed clustering algorithm significantly outperforms the (baseline) clustering algorithms provided by the software EEGLAB, including CORRMAP.

Assessing Functional Brain Network Dynamics in Dyslexia from fNIRS Data.

Developmental dyslexia is characterized by a deficit of phonological awareness whose origin is related to atypical neural processing of speech streams. This can lead to differences in the neural networks that encode audio information for dyslexics. In this work, we investigate whether such differences exist using functional near-infrared spectroscopy (fNIRS) and complex network analysis. We have explored functional brain networks derived from low-level auditory processing of nonspeech stimuli related to speech units such as stress, syllables or phonemes of skilled and dyslexic seven-year-old readers. A complex network analysis was performed to examine the properties of functional brain networks and their temporal evolution. We characterized aspects of brain connectivity such as functional segregation, functional integration or small-worldness. These properties are used as features to extract differential patterns in controls and dyslexic subjects. The results corroborate the presence of discrepancies in the topological organizations of functional brain networks and their dynamics that differentiate between control and dyslexic subjects, reaching an Area Under ROC Curve (AUC) up to 0.89 in classification experiments.

Teachers’ Opinions about the Teaching of Reading in Spain / Las opiniones de los maestros y las maestras acerca de la enseñanza de la lectura en España

Previous research has evidenced which skills are required for reading acquisition and which methods are effective for teaching reading. However, recent research indicated that teachers lack sufficient knowledge about the constructs involved in reading instruction. The purpose of this exploratory study was to examine Spanish teachers’ practice and opinions on reading instruction. Two samples of Spanish teachers, 840 Preschool teachers and 876 Primary teachers, were surveyed about their opinion on reading skills, their reading instruction practices, and methods of detecting and assessing reading difficulties. The questionnaire for primary teachers also included questions on preparedness and knowledge. Most teachers favored whole-word methods, included maturity and motivation, as relevant aids for phonological awareness and showed poor grasp of factors underpinning reading acquisition. Teachers showed inconsistent and limited knowledge of the evidence-based approach for effective reading instruction. Specific programs are needed to provide preservice teachers with evidence-based instruction and continuous training for in service teachers.(AU)

Investigaciones anteriores han señalado qué habilidades son necesarias para la adquisición de la lectura y qué métodos son eficaces para su enseñanza. Sin embargo, investigaciones recientes indican que los profesores carecen de conocimiento suficiente sobre los constructos implicados en la enseñanza de la lectura. Este estudio pretende examinar la práctica y las opiniones de los profesores españoles sobre la enseñanza de la lectura. Se encuestó a dos muestras de profesores españoles, 840 de preescolar y 876 de primaria, sobre sus opiniones acerca de las habilidades lectoras, sus prácticas de enseñanza de la lectura y los métodos de detección y evaluación de las dificultades lectoras. El cuestionario para los profesores de primaria también incluía cuestiones para valorar su preparación y conocimiento. La mayoría de los profesores se inclinaron por los métodos globales y consideraron que la madurez y la motivación son ayudas relevantes para adquirir la conciencia fonológica. Además, mostraron escasa comprensión de los factores que sustentan la adquisición de la lectura. Los profesores manifestaron un conocimiento inconsistente y limitado del enfoque basado en la evidencia para la enseñanza eficaz de la lectura. Se necesitan programas específicos para proporcionar a los profesores en formación una instrucción basada en la evidencia y una formación continua para los profesores en activo.(AU)

Detecting Phase-Synchrony Connectivity Anomalies in EEG Signals. Application to Dyslexia Diagnosis.

Objective Dyslexia diagnosis is a challenging task, since traditional diagnosis methods are not based on biological markers but on behavioural tests. Although dyslexia diagnosis has been addressed by these tests in clinical practice, it is difficult to extract information about the brain processes involved in the different tasks and, then, to go deeper into its biological basis. Thus, the use of biomarkers can contribute not only to the diagnosis but also to a better understanding of specific learning disorders such as dyslexia. In this work, we use Electroencephalography (EEG) signals to discover differences among controls and dyslexic subjects using signal processing and artificial intelligence techniques. Specifically, we measure phase synchronization among channels, to reveal the functional brain network activated during auditory processing. On the other hand, to explore synchronicity patterns risen by low-level auditory processing, we used specific stimuli consisting in band-limited white noise, modulated in amplitude at different frequencies. The differential information contained in the functional (i.e., synchronization) network has been processed by an anomaly detection system that addresses the problem of subjects variability by an outlier-detection method based on vector quantization. The results, obtained for 7 years-old children, show that the proposed method constitutes an useful tool for clinical use, with the area under ROC curve (AUC) values up to 0.95 in differential diagnosis tasks.

Dyslexia Diagnosis by EEG Temporal and Spectral Descriptors: An Anomaly Detection Approach.

Diagnosis of learning difficulties is a challenging goal. There are huge number of factors involved in the evaluation procedure that present high variance among the population with the same difficulty. Diagnosis is usually performed by scoring subjects according to results obtained in different neuropsychological (performance-based) tests specifically designed to this end. One of the most frequent disorders is developmental dyslexia (DD), a specific difficulty in the acquisition of reading skills not related to mental age or inadequate schooling. Its prevalence is estimated between 5% and 12% of the population. Traditional tests for DD diagnosis aim to measure different behavioral variables involved in the reading process. In this paper, we propose a diagnostic method not based on behavioral variables but on involuntary neurophysiological responses to different auditory stimuli. The experiments performed use electroencephalography (EEG) signals to analyze the temporal behavior and the spectral content of the signal acquired from each electrode to extract relevant (temporal and spectral) features. Moreover, the relationship of the features extracted among electrodes allows to infer a connectivity-like model showing brain areas that process auditory stimuli in a synchronized way. Then an anomaly detection system based on the reconstruction residuals of an autoencoder using these features has been proposed. Hence, classification is performed by the proposed system based on the differences in the resulting connectivity models that have demonstrated to be a useful tool for differential diagnosis of DD as well as a method to step towards gaining a better knowledge of the brain processes involved in DD. The results corroborate that nonspeech stimulus modulated at specific frequencies related to the sampling processes developed in the brain to capture rhymes, syllables and phonemes produces effects in specific frequency bands that differentiate between controls and DD subjects. The proposed method showed relatively high sensitivity above 0.6, and up to 0.9 in some of the experiments.

Syllabic parsing in children: a developmental study using visual word-spotting in Spanish.

Some inconsistency is observed in the results from studies of reading development regarding the role of the syllable in visual word recognition, perhaps due to a disparity between the tasks used. We adopted a word-spotting paradigm, with Spanish children of second grade (mean age: 7 years) and sixth grade (mean age: 11 years). The children were asked to detect one-syllable words that could be found at the beginning of pseudo-words, with the boundary between the word and the remaining letters being manipulated. The end of the embedded word could either match the syllabic boundary (e.g. the word FIN in the pseudo-word FINLO, where the syllable boundary is between N and L) or not (e.g. FINUS, where the syllable boundary is located between I and N). The results showed that children of both grades were faster in the syllabic than the non-syllabic condition, and that the magnitude of this effect was the same regardless of reading ability. The results suggest an early universality in the use of syllables in Spanish, regardless of reading level.

De la teoría fonológica a la identificación temprana de las dificultades específicas de aprendizaje de la lectura / From phonological theory to the early detection of specific learning difficulties in reading

Se revisa el marco teórico de investigación generado en torno a la teoría fonológica de la dislexia evolutiva. Este marco ha habilitado la posibilidad de realizar una identificación temprana de las dificultades específicas de aprendizaje de la lectura y ha justificado su necesidad práctica. Cuatro son las aportaciones fundamentales. Primero, la teoría fonológica defiende que la dislexia evolutiva se produce como consecuencia de un déficit fonológico general que afecta a diversos componentes del sistema fonológico, entre los que destacan la conciencia fonológica, la velocidad de los procesos léxicos y la memoria verbal a corto plazo. Segundo, la teoría fonológica ha puesto de manifiesto que la causa primaria de la dislexia está presente desde el periodo embrionario y produce consecuencias sobre el desarrollo del lenguaje oral durante todo el periodo previo al aprendizaje de la lectura. Tercero, la teoría fonológica ha defendido la tesis del lenguaje oral como causa primaria del déficit, y con ello ha revelado las relaciones entre los trastornos específicos del lenguaje y la dislexia evolutiva. Cuarto, la investigación ha mostrado el significativo impacto de los programas de prevención e intervención temprana, lo que obliga a complementar las estrategias reactivas y tardías de diagnóstico, con estrategias proactivas de prevención y/o identificación e intervención temprana. Finalmente, se argumenta que si las causas primeras y los sistemas de prevención e intervención de estas dificultades están directamente vinculados con el desarrollo del lenguaje, entonces la logopedia debería tener un papel protagonista en la implementación de las estrategias proactivas en el contexto escolar (AU)

This paper presents a review of the research issued from the frame of the Phonological Theory of developmental dyslexia. This theory has set up the means to make an early identification of specific learning difficulties in reading, and has provided theoretical support for its implementation. There are four fundamental contributions. First, the Phonological Theory argues that developmental dyslexia is a consequence of a general phonological deficit that affects different components of the phonological system being phonological awareness, lexical processing speed and verbal short-term memory the most relevant. Second, the Phonological Theory has pointed out that the primary cause of dyslexia is present from the embryonic period and that it affects oral language development before learning to read. Third, the Phonological Theory has considered oral language as the main cause of the deficit, and consequently, has highlighted the relations between Specific Language Impairment and Developmental Dyslexia. Fourth, since research has proved the significant impact of Programs for prevention and early intervention, a clear need for adding proactive strategies of early prevention and/or identification to the late reactive diagnosis strategies has arisen. Finally, it is argued that if primary causes as well as prevention and intervention resources are directly attached to language development, then, speech therapists should play a main role in the implementation of proactive strategies in the school context (AU)

A self-report questionnaire on reading-writing difficulties for adults / Autoinforme de Trastornos Lectores para AdultoS (ATLAS)

In this paper a self-report questionnaire on reading-writing difficulties for adults in Spanish (ATLAS) is presented. Studies that use selfreport questionnaires as a tool for screening of reading-writing difficulties in adults were reviewed. Two studies were carried out to determine the validity and reliability of ATLAS. The first study was aimed to select the critical items and to assess their reliability and their ability to discriminate. In the second study the assessment reported through the answers to the questionnaire was contrasted with the results of psychometric tests. Results showed that (a) items were suitable descriptors for adult difficulties, (b) there were significant correlations between self-report scores and reading measures, and (c) the items discriminate between good and poor readers. The results of this study demonstrated that ATLAS is a sensitive tool to screen adults with reading difficulties. As a further advantage, ATLAS is aneasy-to-use and time-saving instrument

En este trabajo se presenta un cuestionario de autoinforme de trastornos lectores para adultos en español (ATLAS). Se comienza por revisar las investigaciones que demuestran la utilidad y la fiabilidad de los autoinformes como instrumento para valorar las habilidades lectoescritoras de los adultos. A continuación se describe un estudio destinado a seleccionar los ítems críticos en función de su capacidad discriminativa. Este estudio permitió la elaboración de la versión final del autoinforme. Finalmente, en un segundo estudio se contrastan los datos recogidos a través del autoinforme con los obtenidos mediante pruebas psicométricas en una población universitaria. Los resultados indican que los ítems permiten (a) describir las principales dificultades de lectoescritura y (b) discriminar entre normolectores y estudiantes con dificultades. Por otra, (c) los resultados muestran que la autovaloración realizada mediante el autoinforme coincide con las medidas obtenidas mediante pruebas objetivas. Estos resultados apoyan la utilidad y fiabilidad del uso del ATLAS para detectar adultos con trastornos de lectoescritura. Presenta, además, la ventaja de ser fácil y rápido de usar

Beyond decoding deficit: inhibitory effect of positional syllable frequency in dyslexic Spanish children.

This study explores whether activation and inhibition word processes contribute to the characteristic speed deficits found in transparent orthographies (Wimmer, Appl Psycholinguist 14:1-33, 1993). A second and fourth grade sample of normal school readers and dyslexic school readers participated in a lexical decision task. Words were manipulated according to two factors: word frequency (high vs. low) and syllable frequency (high vs. low). It has been repeatedly found that words with high-frequency syllables require extra time for deactivating the lexical syllabic neighbors: the so-called inhibitory effect of positional frequency syllable (Carreiras et al., J Mem Lang 32:766-780, 1993). We hypothesized that dyslexic readers would show a stronger inhibitory effect than normal readers because they are slower decoders and they may also be slower at the activation and inhibition of word representations that are competing (i.e., syllabic candidates). Results indicated an interaction between word and syllable frequency (i.e., a strong inhibitory effect was found in the low-frequency word condition). According to our hypothesis, the inhibitory effect size was almost three times bigger in dyslexics than in the normal readers. This difference shows an alteration, not a developmental lag. Interestingly, the inhibitory effect size did not interact with school grade. Thus, reading experience did not impact the lexical processes involved on the inhibitory effect. Our outcomes showed how activation and/or inhibition of lexical processes can contribute to the lack of speed beyond decoding deficit.