Browsing by Author "Bramão, Inês"
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- A aprendizagem implícita em crianças disléxicasPublication . Inácio, Filomena; Faísca, Luís; Forkstam, Christian; Araújo, Susana; Bramão, Inês; Reis, Alexandra; Petersson, Karl MagnusThis 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.
- Cortical brain regions associated with color processing: an FMRI studyPublication . Bramão, Inês; Faísca, Luís; Forkstam, Christian; Reis, Alexandra; Petersson, Karl MagnusTo clarify whether the neural pathways concerning color processing are the same for natural objects, for artifacts objects and for non-objects we examined brain responses measured with functional magnetic resonance imaging (FMRI) during a covert naming task including the factors color (color vs. black&white (B&W)) and stimulus type (natural vs. artifacts vs. non-objects). Our results indicate that the superior parietal lobule and precuneus (BA 7) bilaterally, the right hippocampus and the right fusifom gyrus (V4) make part of a network responsible for color processing both for natural objects and artifacts, but not for non-objects. When color objects (both natural and artifacts) were contrasted with color non-objects we observed activations in the right parahippocampal gyrus (BA 35/36), the superior parietal lobule (BA 7) bilaterally, the left inferior middle temporal region (BA 20/21) and the inferior and superior frontal regions (BA 10/11/47). These additional activations s uggest that colored objects recruit brain regions that are related to visual semantic information/retrieval and brain regions related to visuo-spatial processing. Overall, the results suggest that color information is an attribute that can improve object recognition (behavioral results) and activate a specific neural network related to visual semantic information that is more extensive than for B&W objects during object recognition
- Electrophysiological correlates of impaired reading in dyslexic pre-adolescent childrenPublication . Araújo, Susana; Bramão, Inês; Faísca, Luís; Petersson, Karl Magnus; Reis, AlexandraIn 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.
- Electrophysiological evidence for colour effects on the naming of colour diagnostic and noncolour diagnostic objectsPublication . Bramão, Inês; Francisco, Ana; Inácio, Filomena; Faísca, Luís; Reis, Alexandra; Petersson, Karl MagnusIn this study, we investigated the level of visual processing at which surface colour information improves the naming of colour diagnostic and noncolour diagnostic objects. Continuous electroencephalograms were recorded while participants performed a visual object naming task in which coloured and black-and-white versions of both types of objects were presented. The black-and-white and the colour presentations were compared in two groups of event-related potentials (ERPs): (1) The P1 and N1 components, indexing early visual processing; and (2) the N300 and N400 components, which index late visual processing. A colour effect was observed in the P1 and N1 components, for both colour and noncolour diagnostic objects. In addition, for colour diagnostic objects, a colour effect was observed in the N400 component. These results suggest that colour information is important for the naming of colour and noncolour diagnostic objects at different levels of visual processing. It thus appears that the visual system uses colour information, during naming of both object types, at early visual stages; however, for the colour diagnostic objects naming, colour information is also recruited during the late visual processing stages.
- Implicit sequence learning is preserved in dyslexic childrenPublication . Inácio, Filomena; Faísca, Luís; Forkstam, Christian; Araújo, Susana; Bramão, Inês; Reis, Alexandra; Petersson, Karl MagnusThis 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 influência das competências de leitura nas estratégias de dupla codificaçãoPublication . Inácio, Filomena; Bramão, Inês; Faísca, Luís; Reis, AlexandraRecentemente, alguns autores demonstraram que o desempenho em provas de memória não verbal pode envolver o recurso simultâneo a estratégias verbais e visuo-espaciais para codificar a informação. A leitura tem sido apontada como um factor que pode contribuir para o desenvolvimento destas estratégias de dupla codificação. Neste estudo, fomos investigar se a capacidade de leitura interfere de algum modo na utilização de mecanismos de dupla codificação. Comparámos o desempenho de dois grupos de crianças com diferentes competências de leitura, mas equivalentes na idade e em anos de escolaridade, numa prova de memória não verbal. Foram definidas três condições experimentais, manipulando o grau em que os itens a memorizar eram verbalizáveis. Os resultados mostraram que o grupo com melhores competências de leitura apresenta um desempenho superior na condição pictórica mais difícil de verbalizar quando comparado com o grupo com piores competências de leitura. Estes resultados são discutidos à luz do contributo das competências de leitura na facilitação em utilizar estratégias de dupla codificação para codificar a informação visuo-espacial em memória de trabalho.
- Knowing that strawberries are red and seeing red strawberries: the interaction between surface colour and colour knowledge informationPublication . Bramão, Inês; Reis, Alexandra; Petersson, Karl Magnus; Faísca, LuísThis study investigates the interaction between surface and colour knowledge information during object recognition. In two different experiments, participants were instructed to decide whether two presented stimuli belonged to the same object identity. On the non-matching trials, we manipulated the shape and colour knowledge information activated by the two stimuli by creating four different stimulus pairs: (1) similar in shape and colour (e.g. TOMATO-APPLE); (2) similar in shape and dissimilar in colour (e.g. TOMATO-COCONUT); (3) dissimilar in shape and similar in colour (e.g. TOMATO-CHILI PEPPER) and (4) dissimilar in both shape and colour (e.g. TOMATO-PEANUT). The object pictures were presented in typical and atypical colours and also in black-and-white. The interaction between surface and colour knowledge showed to be contingent upon shape information: while colour knowledge is more important for recognising structurally similar shaped objects, surface colour is more prominent for recognising structurally dissimilar shaped objects.
- Lexical and phonological processes in dyslexic readers: evidence from a visual lexical decision taskPublication . Araújo, Susana; Faísca, Luís; Bramão, Inês; Petersson, Karl Magnus; Reis, AlexandraThe 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.
- Object naming in dyslexic children: more than a phonological deficitPublication . Araújo, Susana; Faísca, Luís; Bramão, Inês; Inácio, Filomena; Petersson, Karl Magnus; Reis, AlexandraIn 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.
- The contribution of color during object recognition: behavioral, electrophysiological and neuroimaging evidencePublication . Bramão, Inês; Petersson, Karl MagnusIn this thesis, we present six studies that investigated the role of color information during visual object recognition. The interactions between surface color and color knowledge information were investigated in two studies (chapters 2 and 3). In chapters 4 and 5, we present data that identify the visual processing stage at which color information improves color and non-color diagnostic object recognition. In chapter 6, the neural pathways supporting color object recognition were investigated. Additionally, in an attempt to bring some consistency to the literature, we performed a systematic meta-analysis on the effects of color on object recognition in chapter 7. Chapter 2 and 3 provided data suggesting that surface color information is more influential than color knowledge information during object recognition. Chapter 4 and 5 showed that color information improves the recognition of color and non-color diagnostic objects at different stages of visual processing. Although color information is an important cue for both of these types of objects in the early visual processes, it is also important in later stages of visual processing for color diagnostic object recognition. In chapter 6, we observed that colored objects, when compared with black and white objects, activated a more extensive brain network related to visuo-semantic activation and retrieval. Finally, the meta-analysis in chapter 7 conclusively showed a significant effect of color information during object recognition. In summary, the general picture that emerges from this body of work is that color information takes part in object recognition processes at multiple levels of representation.