Extending Zipf’s law to n-grams for large corpora

Experiments show that for a large corpus, Zipf’s law does not hold for all rank of words: the frequencies fall below those predicted by Zipf’s law for ranks greater than about 5,000 word types in the English language and about 30,000 word types in the inflected languages Irish and Latin. It also does not hold for syllables or words in the syllable-based languages, Chinese or Vietnamese. However, when single words are combined together with word n-grams in one list and put in rank order, the frequency of tokens in the combined list extends Zipf’s law with a slope close to -1 on a log-log plot in all five languages. Further experiments have demonstrated the validity of this extension of Zipf’s law to n-grams of letters, phonemes or binary bits in English. It is shown theoretically that probability theory
alone can predict this behavior in randomly created n-grams of binary bits.

Language-universal Sensory Deficits in Developmental Dyslexia: English, Spanish, and Chinese

Studies in sensory neuroscience reveal the critical importance of accurate sensory perception for cognitive development. There is considerable debate concerning the possible sensory correlates of phonological processing, the primary cognitive risk factor for developmental dyslexia. Across languages, children with dyslexia have a specific difficulty with the neural representation of the phonological structure of speech. The identification of a robust sensory marker of phonological difficulties would enable early identification of risk for developmental dyslexia and early targeted intervention. Here, we explore whether phonological processing difficulties are associated with difficulties in processing acoustic cues to speech rhythm. Speech rhythm is used across languages by infants to segment the speech stream into words and syllables. Early difficulties in perceiving auditory sensory cues to speech rhythm and prosody could lead developmentally to impairments in phonology. We compared matched samples of children with and without dyslexia, learning three very different spoken and written languages, English, Spanish, and Chinese. The key sensory cue measured was rate of onset of the amplitude envelope (rise time), known to be critical for the rhythmic timing of speech. Despite phonological and orthographic differences, for each language, rise time sensitivity was a significant predictor of phonological awareness, and rise time was the only consistent predictor of reading acquisition. The data support a language-universal theory of the neural basis of developmental dyslexia on the basis of rhythmic perception and syllable segmentation. They also suggest that novel remediation strategies on the basis of rhythm and music may offer benefits for phonological and linguistic development.

Auditory sensory deficits in developmental dyslexia: A longitudinal ERP study

The core difficulty in developmental dyslexia across languages is a "phonological deficit", a specific difficulty with the neural representation of the sound structure of words. Recent data across languages suggest that this phonological deficit arises in part from inefficient auditory processing of the rate of change of the amplitude envelope at syllable onset (inefficient sensory processing of rise time). Rise time is a complex percept that also involves changes in duration and perceived intensity. Understanding the neural mechanisms that give rise to the phonological deficit in dyslexia is important for optimising educational interventions. In a three-deviant passive 'oddball' paradigm and a corresponding blocked 'deviant-alone' control condition we recorded ERPs to tones varying in rise time, duration and intensity in children with dyslexia and typically developing children longitudinally. We report here results from test Phases 1 and 2, when participants were aged 8-10. years. We found an MMN to duration, but not to rise time nor intensity deviants, at both time points for both groups. For rise time, duration and intensity we found group effects in both the Oddball and Blocked conditions. There was a slower fronto-central P1 response in the dyslexic group compared to controls. The amplitude of the P1 fronto-centrally to tones with slower rise times and lower intensity was smaller compared to tones with sharper rise times and higher intensity in the Oddball condition, for children with dyslexia only. The latency of this ERP component for all three stimuli was shorter on the right compared to the left hemisphere, only for the dyslexic group in the Blocked condition. Furthermore, we found decreased N1c amplitude to tones with slower rise times compared to tones with sharper rise times for children with dyslexia, only in the Oddball condition. Several other effects of stimulus type, age and laterality were also observed. Our data suggest that neuronal responses underlying some aspects of auditory sensory processing may be impaired in dyslexia. © 2011 Elsevier Inc.

Do grafema ao gesto : contributos linguísticos para um sistema de síntese de base articulatória

Motivados pelo propósito central de contribuir para a construção, a longo prazo, de um sistema completo de conversão de texto para fala, baseado em síntese articulatória, desenvolvemos um modelo linguístico para o português europeu (PE), com base no sistema TADA (TAsk Dynamic Application), que visou a obtenção automática da trajectória dos articuladores a partir do texto de entrada. A concretização deste objectivo ditou o desenvolvimento de um conjunto de tarefas, nomeadamente 1) a implementação e avaliação de dois sistemas de silabificação automática e de transcrição fonética, tendo em vista a transformação do texto de entrada num formato adequado ao TADA; 2) a criação de um dicionário gestual para os sons do PE, de modo a que cada fone obtido à saída do conversor grafema-fone pudesse ter correspondência com um conjunto de gestos articulatórios adaptados para o PE; 3) a análise do fenómeno da nasalidade à luz dos princípios dinâmicos da Fonologia Articulatória (FA), com base num estudo articulatório e perceptivo. Os dois algoritmos de silabificação automática implementados e testados fizeram apelo a conhecimentos de natureza fonológica sobre a estrutura da sílaba, sendo o primeiro baseado em transdutores de estados finitos e o segundo uma implementação fiel das propostas de Mateus & d'Andrade (2000). O desempenho destes algoritmos – sobretudo do segundo – mostrou-se similar ao de outros sistemas com as mesmas potencialidades. Quanto à conversão grafema-fone, seguimos uma metodologia baseada em regras de reescrita combinada com uma técnica de aprendizagem automática. Os resultados da avaliação deste sistema motivaram a exploração posterior de outros métodos automáticos, procurando também avaliar o impacto da integração de informação silábica nos sistemas. A descrição dinâmica dos sons do PE, ancorada nos princípios teóricos e metodológicos da FA, baseou-se essencialmente na análise de dados de ressonância magnética, a partir dos quais foram realizadas todas as medições, com vista à obtenção de parâmetros articulatórios quantitativos. Foi tentada uma primeira validação das várias configurações gestuais propostas, através de um pequeno teste perceptual, que permitiu identificar os principais problemas subjacentes à proposta gestual. Este trabalho propiciou, pela primeira vez para o PE, o desenvolvimento de um primeiro sistema de conversão de texto para fala, de base articulatória. A descrição dinâmica das vogais nasais contou, quer com os dados de ressonância magnética, para caracterização dos gestos orais, quer com os dados obtidos através de articulografia electromagnética (EMA), para estudo da dinâmica do velo e da sua relação com os restantes articuladores. Para além disso, foi efectuado um teste perceptivo, usando o TADA e o SAPWindows, para avaliar a sensibilidade dos ouvintes portugueses às variações na altura do velo e alterações na coordenação intergestual. Este estudo serviu de base a uma interpretação abstracta (em termos gestuais) das vogais nasais do PE e permitiu também esclarecer aspectos cruciais relacionados com a sua produção e percepção.

Ressonância magnética em estudos de produção de fala

Estudar os mecanismos subjacentes à produção de fala é uma tarefa complexa e exigente, requerendo a obtenção de dados mediante a utilização de variadas técnicas, onde se incluem algumas modalidades imagiológicas. De entre estas, a Ressonância Magnética (RM) tem ganho algum destaque, nos últimos anos, posicionando-se como uma das mais promissoras no domínio da produção de fala. Um importante contributo deste trabalho prende-se com a otimização e implementação de protocolos (RM) e proposta de estratégias de processamento de imagem ajustados aos requisitos da produção de fala, em geral, e às especificidades dos diferentes sons. Para além disso, motivados pela escassez de dados para o Português Europeu (PE), constitui-se como objetivo a obtenção de dados articulatórios que permitam complementar informação já existente e clarificar algumas questões relativas à produção dos sons do PE (nomeadamente, consoantes laterais e vogais nasais). Assim, para as consoantes laterais foram obtidas imagens RM (2D e 3D), através de produções sustidas, com recurso a uma sequência Eco de Gradiente (EG) rápida (3D VIBE), no plano sagital, englobando todo o trato vocal. O corpus, adquirido por sete falantes, contemplou diferentes posições silábicas e contextos vocálicos. Para as vogais nasais, foram adquiridas, em três falantes, imagens em tempo real com uma sequência EG - Spoiled (TurboFLASH), nos planos sagital e coronal, obtendo-se uma resolução temporal de 72 ms (14 frames/s). Foi efetuada aquisição sincronizada das imagens com o sinal acústico mediante utilização de um microfone ótico. Para o processamento e análise de imagem foram utilizados vários algoritmos semiautomáticos. O tratamento e análise dos dados permitiu efetuar uma descrição articulatória das consoantes laterais, ancorada em dados qualitativos (e.g., visualizações 3D, comparação de contornos) e quantitativos que incluem áreas, funções de área do trato vocal, extensão e área das passagens laterais, avaliação de efeitos contextuais e posicionais, etc. No que respeita à velarização da lateral alveolar /l/, os resultados apontam para um /l/ velarizado independentemente da sua posição silábica. Relativamente ao /L/, em relação ao qual a informação disponível era escassa, foi possível verificar que a sua articulação é bastante mais anteriorizada do que tradicionalmente descrito e também mais extensa do que a da lateral alveolar. A resolução temporal de 72 ms conseguida com as aquisições de RM em tempo real, revelou-se adequada para o estudo das características dinâmicas das vogais nasais, nomeadamente, aspetos como a duração do gesto velar, gesto oral, coordenação entre gestos, etc. complementando e corroborando resultados, já existentes para o PE, obtidos com recurso a outras técnicas instrumentais. Para além disso, foram obtidos novos dados de produção relevantes para melhor compreensão da nasalidade (variação área nasal/oral no tempo, proporção nasal/oral). Neste estudo, fica patente a versatilidade e potencial da RM para o estudo da produção de fala, com contributos claros e importantes para um melhor conhecimento da articulação do Português, para a evolução de modelos de síntese de voz, de base articulatória, e para aplicação futura em áreas mais clínicas (e.g., perturbações da fala).

Potenciar a consciência fonológica de crianças pré-escolares em contexto naturalístico

Dissertação apresentada à Escola Superior de Educação de Lisboa para obtenção de grau de mestre em Ciências da Educação Especialidade Intervenção Precoce

Neurophysiological origin of human brain asymmetry for speech and language.

The physiological basis of human cerebral asymmetry for language remains mysterious. We have used simultaneous physiological and anatomical measurements to investigate the issue. Concentrating on neural oscillatory activity in speech-specific frequency bands and exploring interactions between gestural (motor) and auditory-evoked activity, we find, in the absence of language-related processing, that left auditory, somatosensory, articulatory motor, and inferior parietal cortices show specific, lateralized, speech-related physiological properties. With the addition of ecologically valid audiovisual stimulation, activity in auditory cortex synchronizes with left-dominant input from the motor cortex at frequencies corresponding to syllabic, but not phonemic, speech rhythms. Our results support theories of language lateralization that posit a major role for intrinsic, hardwired perceptuomotor processing in syllabic parsing and are compatible both with the evolutionary view that speech arose from a combination of syllable-sized vocalizations and meaningful hand gestures and with developmental observations suggesting phonemic analysis is a developmentally acquired process.

The Role of Sleep in the Selective Reconsolidation of Declarative Memories

While sleep has been shown to be involved in memory consolidation and the selective enhancement of newly acquired memories of future relevance (Wilhelm, et al., 2011), limited research has investigated the role of sleep or future relevance in processes of memory reconsolidation. The current research employed a list-method directed forgetting procedure in which participants learned two lists of syllable pairs on Night 1 and received directed forgetting instructions on Night 2. On Night 2, one group (Labile; n = 15) received a memory reactivation treatment consisting of reminders designed to return memories of the learned lists to a labile state. A second group (Stable, n = 16) received similar reminders designed to leave memories of the learned lists in their stable state. No differences in forgetting were found across the two lists or groups. However, a negative correlation between frontal delta (1 – 4 Hz) electroencephalographic (EEG) power during Early Stage 2 non-rapid eye movement (NREM) sleep and forgetting of to-beremembered material was found exclusively in the Labile group (r = -.61, p < .05). Further, central theta (4 – 8 Hz ) EEG power during rapid eye movement (REM) sleep was found to correlate with directed forgetting exclusively in the Labile group (r = .81, p < .001) and total forgetting in the Stable group (r = .50, p < .05). These observed relationships support the proposed hypothesis suggesting that sleep processes are involved in the reconsolidation of labile memories, and that this reconsolidation may be selective for memories of future relevance. A role for sleep in the beneficial reprocessing of memories through the selective reconsolidation of labile memories in NREM sleep and the weakening of memories in REM sleep is discussed.

L'influence d'un modèle sur le chant des amusiques : une solution au chant faux?

L’objectif était d’évaluer l’influence de la mémoire mélodique sur le chant des personnes souffrant d’amusie congénitale. Onze « amusiques » et 11 contrôles appariés ont chanté une chanson familière sur les paroles originales ainsi que sur la syllabe /la/. Les participants ont d’abord chanté la mélodie de mémoire et ensuite, ils ont imité la mélodie après et à l’unisson avec un modèle enregistré préalablement. Les résultats ont illustré que les amusiques ont amélioré leur performance en chantant par imitation (soit après, soit à l’unisson avec le modèle). Ceux qui présentaient une difficulté plus importante de la mémoire ont profité davantage du modèle, particulièrement lorsqu’ils chantaient sur la syllabe /la/. Ces résultats suggèrent qu’une mémoire faible pourrait être une cause des difficultés en chant. De plus, cette étude illustre que le chant par imitation semble être une méthode à privilégier pour améliorer la performance chantée.

Développement du chant et profil d'amusie congénitale chez l'enfant

La musique est universelle et le chant est le moyen d’expression musicale le plus accessible à tous. Les enfants chantent spontanément entre un an et un an et demi (Ostwald, 1973). Pourtant, le développement de cette habileté est très peu étudié en neuropsychologie et ce, malgré le fait qu’elle représente une immense source d’informations sur le traitement de la musique par le cerveau. Les études proposées ici visaient à mieux comprendre le développement normal et pathologique des fonctions perceptives et vocales. Dans un premier temps, une étude sur le chant normal chez les enfants de 6 à 11 ans est présentée. Le développement du chant de 79 enfants d’âge scolaire y est analysé de manière systématique et objective. Cette étude se penche plus particulièrement sur l’influence de l’âge ainsi que d’autres facteurs (le genre, la perception musicale, la présence de paroles et la présence d’un accompagnement vocal) sur la qualité du chant. Les jeunes participants ont chanté une chanson familière dans différentes conditions, soit avec et sans paroles, après un modèle ainsi qu’à l’unisson avec ce dernier. Suite à l’analyse acoustique des performances, différentes variables mélodiques et rythmiques telles que le nombre d’erreurs d’intervalles, le nombre d’erreurs de contours, la taille des déviations d’intervalles, le nombre d’erreurs rythmiques, la taille des déviations temporelles et le tempo, ont été calculés. Les résultats montrent que certaines habiletés de base liées au chant se développent toujours après 6 ans. Toutefois, le rythme est maîtrisé plus tôt, et les enfants d’âges scolaires réussissent parfois mieux que les adultes sur le plan rythmique. De plus, il est plus difficile pour les enfants de chanter avec des ii paroles que sur une syllabe et chanter à l’unisson représente un défi plus grand que chanter après un modèle. Par ailleurs, le nombre d’erreurs de contours, d’intervalles et de rythme, de même que la taille des erreurs rythmiques, sont liés à nos mesures de perception musicale. La seconde étude présente le premier cas documenté d’amusie congénitale chez l’enfant. Elle implique l’analyse de la perception musicale et du chant d’une fillette de 10 ans nous ayant été référée par son directeur de chorale. De sévères déficits ont été relevés chez elle et un diagnostic d’amusie congénitale fut posé. En effet, ses résultats aux tests visant à évaluer sa perception musicale indiquent d’importantes difficultés tant sur le plan de la discrimination des différences mélodiques et rythmiques, qu’au niveau de la mémoire des mélodies. La fillette présente des lacunes claires quant à la perception des fines différences de hauteurs. L’analyse des réponses cérébrales en potentiels évoqués suggère que l’enfant souffre de déficits situés tôt au cours des processus de traitement auditif, tel que démontré par l’absence de négativité de discordance (MMN). Le chant de la jeune fille est lui aussi déficitaire, particulièrement en ce qui concerne le nombre d’erreurs d’intervalles et leurs tailles. En conclusion, nos études montrent que les aptitudes pour le chant sont toujours en développement au cours des premières années de scolarisation. Ce développement peut être entravé par la présence d’un déficit lié spécifiquement à la perception musicale. Pour la première fois, l’amusie congénitale, sera décrite chez l’enfant.

A Classification of Sandhi Rules for Suffix Separation in Malayalam

Suffix separation plays a vital role in improving the quality of training in the Statistical Machine Translation from English into Malayalam. The morphological richness and the agglutinative nature of Malayalam make it necessary to retrieve the root word from its inflected form in the training process. The suffix separation process accomplishes this task by scrutinizing the Malayalam words and by applying sandhi rules. In this paper, various handcrafted rules designed for the suffix separation process in the English Malayalam SMT are presented. A classification of these rules is done based on the Malayalam syllable preceding the suffix in the inflected form of the word (check_letter). The suffixes beginning with the vowel sounds like ആല, ഉെെ, ഇല etc are mainly considered in this process. By examining the check_letter in a word, the suffix separation rules can be directly applied to extract the root words. The quick look up table provided in this paper can be used as a guideline in implementing suffix separation in Malayalam language

Efecto de la frecuencia léxica y silábica en afasia anómica

Objetivo: este estudio compara el desempeño de dos grupos de participantes con y sin afasia anómica en tareas de decisión léxica (TDL) y de deletreo en relación con el efecto de las variables de frecuencia léxica y silábica. Materiales y métodos: se realizó un estudio prospectivo con un diseño 2x2x2, donde se administraron la TDL, en la cual cada participante debía decidir si el estímulo presentado correspondía a palabra o pseudopalabra y la tarea de deletreo, donde los participantesdebían deletrear de forma oral cada una de las palabras presentadas auditivamente. Resultados: para la TDL, el grupo experimental presentó mayor porcentaje de error en los estímulos de alta frecuencia silábica, mientras que el control tuvo más errores en aquellos de baja frecuencia silábica. En cuanto a los tiempos de reacción, el grupo experimental tardó más que los controles en resolver la tarea. La tarea de deletreo no mostró diferencia de ejecución por grupos ni condiciones(frecuencia léxica y silábica). Conclusiones: los resultados del presente estudio demuestran el efecto de facilitación de la frecuencia léxica y la inhibición que genera la frecuencia silábica alta, ampliamente soportada por la investigación en población normatizada mediante diferentes lenguajes.

The development of a phonetically balanced word recognition test in the Ilocano language

Three different phonetically-balanced 50-word recognition lists were constructed in the Ilocano language. Factors that were considered in the construction of these lists were: phonetic balance, syllable structure, and commonness of words.

The relationship between phonological awareness and word reading accuracy in Oriya and English: A Study of Oriya-speaking fifth-graders

This study investigated the relationships between phonological awareness and reading in Oriya and English. Oriya is the official language of Orissa, an eastern state of India. The writing system is an alphasyllabary. Ninety-nine fifth grade children (mean age 9 years 7 months) were assessed on measures of phonological awareness, word reading and pseudo-word reading in both languages. Forty-eight of the children attended Oriya-medium schools where they received literacy instruction in Oriya from grade 1 and learned English from grade 2. Fifty-one children attended English-medium schools where they received literacy instruction in English from grade 1 and in Oriya from grade 2. The results showed that phonological awareness in Oriya contributed significantly to reading Oriya and English words and pseudo-words for the children in the Oriya-medium schools. However, it only contributed to Oriya pseudo-word reading and English word reading for children in the English-medium schools. Phonological awareness in English contributed to English word and pseudo-word reading for both groups. Further analyses investigated the contribution of awareness of large phonological units (syllable, onsets and rimes) and small phonological units (phonemes) to reading in each language. The data suggest that cross-language transfer and facilitation of phonological awareness to word reading is not symmetrical across languages and may depend both on the characteristics of the different orthographies of the languages being learned and whether the first literacy language is also the first spoken language.

Dissociating word stem completion and cued recall as a function of divided attention at retrieval

The aim of this study was to investigate the widely held, but largely untested, view that implicit memory (repetition priming) reflects an automatic form of retrieval. Specifically, in Experiment 1 we explored whether a secondary task (syllable monitoring), performed during retrieval, would disrupt performance on explicit (cued recall) and implicit (stem completion) memory tasks equally. Surprisingly, despite substantial memory and secondary costs to cued recall when performed with a syllable-monitoring task, the same manipulation had no effect on stem completion priming or on secondary task performance. In Experiment 2 we demonstrated that even when using a particularly demanding version of the stem completion task that incurred secondary task costs, the corresponding disruption to implicit memory performance was minimal. Collectively, the results are consistent with the view that implicit memory retrieval requires little or no processing capacity and is not seemingly susceptible to the effects of dividing attention at retrieval.