dyslexia

• Dyslexia is characterized by poor reading skills, yet often also difficulties in second-language learning
• The differences between native- and second-language speech processing and the establishment of new brain representations for spoken second language in dyslexia are not well understood
• The activation of brain representations for familiar second-language words, but not for second-language speech sounds or native-language words, was weaker in children with dyslexia than in typical readers

  
• Source localization revealed that dyslexia was associated with weak activation of the right temporal cortex, which has been previously linked with word-form learning

  
• The amplitude of the mismatch negativity for familiar second-language words


  Correlated with native-language literacy and rapid naming scores
• The findings suggest a close link between second-language processing and native-language literacy and related skills in dyslexia
• Dyslexia is typically characterized by a phonological deficit, including deficient phonological awareness, phonological working memory, and rapid automatized naming (RAN)
• The phonological deficit may be linked with inefficient auditory processing since newborn infants at risk for dyslexia show atypical pattern of auditory event-related potentials (ERP)
• Phonological representations may be intact in dyslexia, whereas access to phonological units is compromised
• In dyslexia, impaired reading in the native language is not the only outcome of underlying phonological processing difficulties. Dyslexic readers often struggle with learning a foreign or a second language, resulting in poor proficiency in this academically and socially important skill
• Recent findings showing deficient functional connectivity through the arcuate fasciculus in dyslexia may be critical for explaining dyslexic readers' difficulties in second-language learning

  
• The left frontal areas have been suggested to participate in the categorization of speech sounds and the establishment of non-native phonetic categories, but their participation depends on their connections with auditory cortex in the temporal lobe, a candidate tract being the arcuate fasciculus
• The left arcuate fasciculus has been suggested to mediate word learning, and its weak connectivity in dyslexia may result in poor second-language learning
• It is unclear whether the 'bottleneck' of spoken second-language learning in dyslexia is the establishment of sublexical (phonetic or phonemic) representations or lexical representations that consist of word forms linked with meaning
• Findings suggest intact processing of native and foreign phonetic segments but impaired learning of native or non-native word forms in dyslexia, suggesting that the bottleneck is the establishment of new word representations, specifically that of word forms required for full lexical representations
• It is not clear whether children with or without dyslexia show a different pattern of activation of neural representations for familiar native-language and second-language words

  
• The mismatch negativity (MMN) component of auditory event-related potential was used to tap the brain representations for spoken native-language and second-language word forms

  
• The MMN is elicited even when attention is directed away from stimulation, which may be particularly important when studying developmental disorders
• Rapid naming


  Typically impaired in dyslexia
• Dyslexia is often accompanied by difficulties in second-language learning
• The study was approved by the Ethical Committee of Helsinki University's Faculty of Behavioural Sciences
• Participation was voluntary
• Participants and their caregivers gave informed oral or written consent, respectively
• Participants


  1. 11-year-old native speakers of Finnish, who studied English as a second language in school
• Pre-tests and background screening

  • Literacy
  • Intelligence
  • Phonological skills
• Literacy assessment


  ALLU: Segmentation of letter strings lacking spaces into words within 3.5 min

  LukiLasse: Accuracy and speed of reading single words aloud within 2 min and writing dictated words or sentences without time limit
• Intelligence assessment


  Wechsler Intelligence Scale for Children IV (WISC): Block design, digit span, vocabulary, and coding
• Naming assessment


  Rapid Alternating Naming test (RAN): Color and letter tasks
• Phonological awareness assessment


  Common unit test: Naming a common phoneme in two auditorily presented pseudowords
• To be included in the study, all children had to reach the criterion of not having scores below one standard deviation in any WISC subtest included in the study
• Criteria for inclusion in the dyslexia group


  • Standard score in the single word reading task was at least one standard deviation below the average

  2a) Standard score in the dictation task was at least one standard deviation below the average

  2b) Scores in the technical reading task belonged to the weakest 23%

  
• Criteria for inclusion in the control group

  • No dyslexia suspicions

  Standard scores in the single word reading and dictation tasks being no more than one standard deviation below the average

  Scores of the technical reading task not belonging to the weakest 23%

  
• All participants had lived their life in a Finnish-speaking environment except one child with dyslexia who had been exposed to English between 2 and 4 years of age while living abroad
• According to parental reports, the children had no other neurological problems, had normal hearing, and were right-handed, with the exception of two control children being left-handed
• Parents reported that outside school, children with or without dyslexia were exposed to English TV programs for 3.5 and 3 h and English games for 2 and 1.9 h per week, respectively
• Differences between dyslexia and control groups

  • Controls outperformed the children with dyslexia in digit span, RAN, and phonological awareness

  No differences in WISC block design, vocabulary, and coding tasks

  
• Differences between dyslexia subgroups (with/without diagnosis)

  • Children without a diagnosis outperformed those with a diagnosis in dictation

  Children with a diagnosis named letters faster than those without a diagnosis

  No differences in word reading, technical reading, phonological awareness or RAN colors

  
• Regardless of diagnosis, all children in the dyslexia group had scores falling to the lowest 10th percentile in word reading

  
• The observed differences between dyslexia subgroups were likely due to factors other than the severity of dyslexia, such as time constraints and ascertainment bias
• Stimuli


  Spoken English and Finnish words and pseudowords