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  • Implicit sequence learning is preserved in dyslexic children
    Publication . Inácio, Filomena; Faísca, Luís; Forkstam, Christian; Araújo, Susana; Bramão, Inês; Reis, Alexandra; Petersson, Karl Magnus
    This study investigates the implicit sequence learning abilities of dyslexic children using an artificial grammar learning task with an extended exposure period. Twenty children with developmental dyslexia participated in the study and were matched with two control groups-one matched for age and other for reading skills. During 3 days, all participants performed an acquisition task, where they were exposed to colored geometrical forms sequences with an underlying grammatical structure. On the last day, after the acquisition task, participants were tested in a grammaticality classification task. Implicit sequence learning was present in dyslexic children, as well as in both control groups, and no differences between groups were observed. These results suggest that implicit learning deficits per se cannot explain the characteristic reading difficulties of the dyslexics.
  • A aprendizagem implícita em crianças disléxicas
    Publication . Inácio, Filomena; Faísca, Luís; Forkstam, Christian; Araújo, Susana; Bramão, Inês; Reis, Alexandra; Petersson, Karl Magnus
    This study investigates the implicit sequence learning abilities of dyslexic children using an artificial grammar learning task and an extended exposure period. Twenty children with developmental dyslexia participated in the study and were matched with two control groups—one matched for age and the second for reading skills. During 3 days, all participants performed an acquisition task in which they were exposed to sequences of colored geometrical forms with an underlying grammatical structure. On the last day, after the acquisition task, participants were tested in a grammaticality classification task. Sequence learning was present in dyslexic children, as well as in both control groups, and no differences between groups were observed. These results suggest that implicit learning deficits cannot explain the characteristic reading difficulties of the dyslexics.
  • Electrophysiological correlates of impaired reading in dyslexic pre-adolescent children
    Publication . Araújo, Susana; Bramão, Inês; Faísca, Luís; Petersson, Karl Magnus; Reis, Alexandra
    In this study, event related potentials (ERPs) were used to investigate the extent to which dyslexics (aged 9–13 years) differ from normally reading controls in early ERPs, which reflect prelexical orthographic processing, and in late ERPs, which reflect implicit phonological processing. The participants performed an implicit reading task, which was manipulated in terms of letter-specific processing, orthographic familiarity, and phonological structure. Comparing consonant- and symbol sequences, the results showed significant differences in the P1 and N1 waveforms in the control but not in the dyslexic group. The reduced P1 and N1 effects in pre-adolescent children with dyslexia suggest a lack of visual specialization for letter-processing. The P1 and N1 components were not sensitive to the familiar vs. less familiar orthographic sequence contrast. The amplitude of the later N320 component was larger for phonologically legal (pseudowords) compared to illegal (consonant sequences) items in both controls and dyslexics. However, the topographic differences showed that the controls were more left-lateralized than the dyslexics. We suggest that the development of the mechanisms that support literacy skills in dyslexics is both delayed and follows a non-normal developmental path. This contributes to the hemispheric differences observed and might reflect a compensatory mechanism in dyslexics.
  • Object naming in dyslexic children: more than a phonological deficit
    Publication . Araújo, Susana; Faísca, Luís; Bramão, Inês; Inácio, Filomena; Petersson, Karl Magnus; Reis, Alexandra
    In the present study, the authors investigate how some visual factors related to early stages of visual-object naming modulate naming performance in dyslexia. The performance of dyslexic children was compared with 2 control groups—normal readers matched for age and normal readersmatched for reading level—while performing a discrete naming task in which color and dimensionality of the visually presented objects were manipulated. The results showed that 2-dimensional naming performance improved for color representations in control readers but not in dyslexics. In contrast to control readers, dyslexics were also insensitive to the stimulus’s dimensionality. These findings are unlikely to be explained by a phonological processing problem related to phonological access or retrieval but suggest that dyslexics have a lower capacity for coding and decoding visual surface features of 2-dimensional representations or problems with the integration of visual information stored in long-term memory.
  • Lexical and phonological processes in dyslexic readers: evidence from a visual lexical decision task
    Publication . Araújo, Susana; Faísca, Luís; Bramão, Inês; Petersson, Karl Magnus; Reis, Alexandra
    The aim of the present study was to investigate whether reading failure in the context of an orthography of intermediate consistency is linked to inefficient use of the lexical orthographic reading procedure. The performance of typically developing and dyslexic Portuguese-speaking children was examined in a lexical decision task, where the stimulus lexicality, word frequency and length were manipulated. Both lexicality and length effects were larger in the dyslexic group than in controls, although the interaction between group and frequency disappeared when the data were transformed to control for general performance factors.
  • The interaction between surface color and color knowledge: behavioral and electrophysiological evidence
    Publication . Bramão, Inês; Faísca, Luís; Forkstam, Christian; Inácio, Filomena; Araújo, Susana; Petersson, Karl Magnus; Reis, Alexandra
    In this study, we used event-related potentials (ERPs) to evaluate the contribution of surface color and color knowledge information in object identification. We constructed two color-object verification tasks – a surface and a knowledge verification task – using high color diagnostic objects; both typical and atypical color versions of the same object were presented. Continuous electroencephalogram was recorded from 26 subjects. A cluster randomization procedure was used to explore the differences between typical and atypical color objects in each task. In the color knowledge task, we found two significant clusters that were consistent with the N350 and late positive complex (LPC) effects. Atypical color objects elicited more negative ERPs compared to typical color objects. The color effect found in the N350 time window suggests that surface color is an important cue that facilitates the selection of a stored object representation from long-term memory. Moreover, the observed LPC effect suggests that surface color activates associated semantic knowledge about the object, including color knowledge representations. We did not find any significant differences between typical and atypical color objects in the surface color verification task, which indicates that there is little contribution of color knowledge to resolve the surface color verification. Our main results suggest that surface color is an important visual cue that triggers color knowledge, thereby facilitating object identification.