Developmental dyslexia: A motor‐articulatory feedback hypothesis

Abstract

Reading is mediated by parallel and widely distributed modular systems. There are, therefore, multiple loci in these systems where dysfunction may lead to developmental dyslexia. However, most normal children learn to read using the alphabetic system. Learning to use this system requires awareness that words are comprised of a system of speech sounds (phonological awareness) and the knowledge of how to convert letters (graphemes) into these speech sounds (phonemes). Most dyslexic children have deficient phonological awareness and have difficulty converting graphemes into phonemes. Studies of patients with acquired lesions who are unable to convert graph-emes into phonemes, as well as positron emission tomographic studies of normal subjects, suggest that the left inferior frontal lobe is important in phonologic reading. Phonetic gestures are represented in the brain as invariant motor commands that program the articulators. Phonologic reading may activate the left inferior frontal lobe because grapheme-to-phoneme conversion requires activation of these motor-articulatory gestures. Dyslexic children are unaware of the position of their articulators during speech. The inability to associate the position of their articulators with speech sounds may impair the development of phonological awareness and the ability to convert graphemes to phonemes. Unawareness of their articulators may be related to programming or feedback deficits.

A importância da equipe interdisciplinar no diagnóstico de dislexia do desenvolvimento: relato de caso

“…Na última década, estudos neuropsicológicos sugerem que o substrato neurológico da leitura parece envolver mais do que o giro superior do lobo temporal. Um estudo 5 empregando MRI em grupos de disléxicos (n=17), leitores atrasados (n=6) e sujeitos controle (n=12), encontrou diferenças mais pronunciadas nas medidas das áreas de cruzamento regional do córtex temporal com a substância branca subcortical, em particular a lateral da insula. Enquanto muitos dos leitores normais e atrasados (72%) tinham assimetria esquerda, a maioria dos dis-léxicos (83%) tinham assimetria direita ou medidas simétricas.…”

“…Portanto, um único profissional não basta para analisar esses vários aspectos e fornecer diagnóstico preciso e seguro. Dislexia do desenvolvimento é disfunção do sistema nervoso central, frequentemente de origem constitucional, caracterizada pela dificuldade na aquisição ou no uso da leitura e/ou escrita, que acomete crianças com inteligência normal, sem défices sensoriais, com instrução supostamente adequada e na ausência de problemas físicos ou emocionais significativos [2][3][4][5] . Boder (1973) 6 distinguiu três tipos de disléxicos (disfonéticos, diseidéticos e mistos) baseando-se nos tipos de erros produzidos nas diversas condições de leitura (palavras familiares ou não familiares, longas ou curtas, de alta ou baixa frequência).…”

“…Portanto, um único profissional não basta para analisar esses vários aspectos e fornecer diagnóstico preciso e seguro. Dislexia do desenvolvimento é disfunção do sistema nervoso central, frequentemente de origem constitucional, caracterizada pela dificuldade na aquisição ou no uso da leitura e/ou escrita, que acomete crianças com inteligência normal, sem défices sensoriais, com instrução supostamente adequada e na ausência de problemas físicos ou emocionais significativos [2][3][4][5] .…”

Προσχολικοί Δείκτες Πρόβλεψης Της Αναγνωστικής Επίδοσης

“…Γενικά υπάρχουν σαφής ενδείξεις ότι η παρεγκεφαλίδα εμπλέκεται στη γλώσσα και τις γνωστικές δεξιότητες (Allen et al, 1997• Thach, 1996• Andreou, Vlachos & Haftouras, 2007• Riva & Giorgi, 2000• Silveri & Misciagna, 2000. Η υπόθεση παρέχει ένα ενδεχομένως ενοποιημένο πλαίσιο για τη δυσλεξία, ισχυριζόμενη ότι η παρεγκεφαλιδική εξασθένιση προκαλεί αρθρωτικές δυσκολίες και, από εκεί και πέρα φωνολογικά προβλήματα (Heilman et al, 1996• Snowling & Hulme, 1994. Σύμφωνα με τη θεωρία, η μειωμένη ταχύτητα άρθρωσης που μπορεί να παρουσιάζει ένα παιδί με παρεγκεφαλιδική δυσλειτουργία οδηγεί τελικά σε φτωχή εργαζόμενη μνήμη, που είναι επίσης χαρακτηριστικό των παιδιών με δυσλεξία (Fawcett & Nicolson, 1999).…”

“…Η υπόθεση παρέχει επιπλέον ένα ενδεχομένως ενοποιημένο πλαίσιο για τη δυσλεξία, ισχυριζόμενη ότι η παρεγκεφαλιδική εξασθένιση προκαλεί αρθρωτικές δυσκολίες και, από εκεί και πέρα φωνολογικά προβλήματα (Heilman, Voeller, & Alexander, 1996• Snowling & Hulme, 1994) που οδηγούν στις αναγνωστικές δυσκολίες. Επιπλέον, ένα παρεγκεφαλιδικό έλλειμμα θα οδηγούσε στην επιβράδυνση της ταχύτητας επεξεργασίας (υπόθεση διπλού ελλείμματος) και σε ελλείμματα στην κινητική ικανότητα.…”