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- 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.
- 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
- 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.
- The influence of surface color information and color knowledge information in object recognitionPublication . Bramão, Inês; Faísca, Luís; Petersson, Karl Magnus; Reis, AlexandraIn order to clarify whether the influence of color knowledge information in object recognition depends on the presence of the appropriate surface color, we designed a name-object verification task. The relationship between color and shape information provided by the name and by the object photo was manipulated in order to assess color interference independently of shape interference. We tested three different versions for each object: typically colored, black and white, and nontypically colored. The response times on the nonmatching trials were used to measure the interference between the name and the photo. We predicted that the more similar the name and the photo are, the longer it would take to respond. Overall, the color similarity effect disappeared in the black-and-white and nontypical color conditions, suggesting that the influence of color knowledge on object recognition depends on the presence of the appropriate surface color information.
- 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 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.
- The contribution of color to object recognitionPublication . Bramão, Inês; Faísca, Luís; Petersson, Karl Magnus; Reis, AlexandraThe cognitive processes involved in object recognition remain a mystery to the cognitive sciences. We know that the visual system recognizes objects via multiple features, including shape, color, texture, and motion characteristics. However, the way these features are combined to recognize objects is still an open question. The purpose of this contribution is to review the research about the specific role of color information in object recognition. Given that the human brain incorporates specialized mechanisms to handle color perception in the visual environment, it is a fair question to ask what functional role color might play in everyday vision.
- The effects of literacy and education on the quantitative and qualitative aspects of semantic verbal fluencyPublication . Mendonça, Alexandra; Bramão, Inês; Faísca, Luís; Petersson, Karl Magnus; Reis, AlexandraSemantic verbal fluency tasks are commonly used in neuropsychological assessment. Investigations of the influence of level of literacy have not yielded consistent results in the literature. This prompted us to investigate the ecological relevance of task specifics, in particular, the choice of semantic criteria used. Two groups of literate and illiterate subjects were compared on two verbal fluency tasks using different semantic criteria. The performance on a food criterion (supermarket fluency task), considered more ecologically relevant for the two literacy groups, and an animal criterion (animal fluency task) were compared. The data were analysed using both quantitative and qualitative measures. The quantitative analysis indicated that the two literacy groups performed equally well on the supermarket fluency task. In contrast, results differed significantly during the animal fluency task. The qualitative analyses indicated differences between groups related to the strategies used, especially with respect to the animal fluency task. The overall results suggest that there is not a substantial difference between literate and illiterate subjects related to the fundamental workings of semantic memory. However, there is indication that the content of semantic memory reflects differences in shared cultural background – in other words, formal education –, as indicated by the significant interaction between level of literacy and semantic criterion.
- 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.
- The impact of reading and writing skills on a visual-motor integration task: a comparison between illiterate and literate subjectsPublication . Bramão, Inês; Petersson, Karl Magnus; Faísca, Luís; Ingvar, Martin; Mendonça, Alexandra; Reis, AlexandraPrevious studies have shown a significant association between reading skills and the performance on visuo-motor tasks. In order to clarify whether reading and writing skills modulate non-linguistic domains, we investigated the performance of two literacy groups on a visuo-motor integration task with non-linguistic stimuli. Twenty-one illiterate participants and twenty matched literate controls were included in the experiment. Subjects were instructed to use the right or the left index finger to point to and touch a randomly presented target on the right or left side of a touch screen. The results showed that the literate subjects were significantly faster in detecting and touching targets on the left compared to the right side of the screen. In contrast, the presentation side did not affect the performance of the illiterate group. These results lend support to the idea that having acquired reading and writing skills, and thus a preferred left-to-right reading direction, influences visual scanning.