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- Implicit structured sequence learning: an fMRI study of the structural mere-exposure effectPublication . Folia, Vasiliki; Petersson, Karl MagnusIn this event-related fMRI study we investigated the effect of 5 days of implicit acquisition on preference classification by means of an artificial grammar learning (AGL) paradigm based on the structural mere-exposure effect and preference classification using a simple right-linear unification grammar. This allowed us to investigate implicit AGL in a proper learning design by including baseline measurements prior to grammar exposure. After 5 days of implicit acquisition, the fMRI results showed activations in a network of brain regions including the inferior frontal (centered on BA 44/45) and the medial prefrontal regions (centered on BA 8/32). Importantly, and central to this study, the inclusion of a naive preference fMRI baseline measurement allowed us to conclude that these fMRI findings were the intrinsic outcomes of the learning process itself and not a reflection of a preexisting functionality recruited during classification, independent of acquisition. Support for the implicit nature of the knowledge utilized during preference classification on day 5 come from the fact that the basal ganglia, associated with implicit procedural learning, were activated during classification, while the medial temporal lobe system, associated with explicit declarative memory, was consistently deactivated. Thus, preference classification in combination with structural mere-exposure can be used to investigate structural sequence processing (syntax) in unsupervised AGL paradigms with proper learning designs.
- Literacy: exploring working memory systemsPublication . Silva, Catarina; Faísca, Luís; Ingvar, Martin; Petersson, Karl Magnus; Reis, AlexandraPrevious research showed an important association between reading and writing skills (literacy) and the phonological loop. However, the effects of literacy on other working memory components remain unclear. In this study, we investigated performance of illiterate subjects and their matched literate controls on verbal and nonverbal working memory tasks. Results revealed that the phonological loop is significantly influenced by literacy, while the visuospatial sketchpad appears to be less affected or not at all. Results also suggest that the central executive might be influenced by literacy, possibly as an expression of cognitive reserve.
- Implicit acquisition of grammars with crossed and nested non-adjacent dependencies: investigating the push-down stack modelPublication . Udden, Julia; Ingvar, Martin; Hagoort, Peter; Petersson, Karl MagnusA recent hypothesis in empirical brain research on language is that the fundamental difference between animal and human communication systems is captured by the distinction between finite-state and more complex phrase-structure grammars, such as context-free and context-sensitive grammars. However, the relevance of this distinction for the study of language as a neurobiological system has been questioned and it has been suggested that a more relevant and partly analogous distinction is that between non-adjacent and adjacent dependencies. Online memory resources are central to the processing of non-adjacent dependencies as information has to be maintained across intervening material. One proposal is that an external memory device in the form of a limited push-down stack is used to process non-adjacent dependencies. We tested this hypothesis in an artificial grammar learning paradigm where subjects acquired non-adjacent dependencies implicitly. Generally, we found no qualitative differences between the acquisition of non-adjacent dependencies and adjacent dependencies. This suggests that although the acquisition of non-adjacent dependencies requires more exposure to the acquisition material, it utilizes the same mechanisms used for acquiring adjacent dependencies. We challenge the push-down stack model further by testing its processing predictions for nested and crossed multiple non-adjacent dependencies. The push-down stack model is partly supported by the results, and we suggest that stack-like properties are some among many natural properties characterizing the underlying neurophysiological mechanisms that implement the online memory resources used in language and structured sequence processing.
- Semantic interference on a phonological task in illiterate subjectsPublication . Reis, Alexandra; Faísca, Luís; Mendonca, Susana; Ingvar, Martin; Petersson, Karl MagnusScandinavian Journal of Psychology, 2007, 48, 69–74 DOI: 10.1111/j.1467-9450.2006.00544.x © 2007 The Authors. Journal compilation © 2007 The Scandinavian Psychological Associations. Published by Blackwell Publishing L td., 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA. ISSN 0036-5564. Blackwell Publishing Ltd Health and Disability Semantic interference on a phonological task in illiterate subjects ALEXANDRA REIS, 1,2,3 L UÍS FAÍSCA, 2,3 SUSANA MENDONÇA, 2 MARTIN INGVAR 1 and KARL MAGNUS PETERSSON 1,3,4 1 Cognitive Neurophysiology Research Group, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden 2 Cognitive Neuroscience Research Group, Departamento de Psicologia, Faculdade de Ciências Humanas e Sociais, Universidade do Alg arve, Faro, Por tugal 3 Center for Intelligent Systems, Universidade do Algarve, Faro, Portugal 4 F. C. Donders Centre for Cognitive Neuroimaging, Radboud University Nijmegen, The Netherlands R eis, A., Faísca, L., Mendonça, S., Ingvar, M. & Petersson, K. M. (2007). Semantic interference on a phonological task in illit erate subjects. Scandinavian Journal of Psychology , 48 , 69–74. Previous research suggests that learning an alphabetic written language influences aspects of the auditory-verbal language syste m. In this study, we e xamined whether literacy influences the notion of words as phonological units independent of lexical semantics in literate a nd illiterate subjects. Subjects had to decide which item in a word- or pseudoword pair was phonologically longest. By manipulating the relat ionship between r eferent size and phonological length in three word conditions (congruent, neutral, and incongruent) we could examine to what e xtent subjects f ocused on form rather than meaning of the stimulus material. Moreover, the pseudoword condition allowed us to examine global p honological aw areness independent of lexical semantics. The results showed that literate performed significantly better than illiterate subj ects in the neutral and incongruent word conditions as well as in the pseudoword condition. The illiterate group performed least well in the incong ruent condition and significantly better in the pseudoword condition compared to the neutral and incongruent word conditions and suggest that pe rformance on phonological word length comparisons is dependent on literacy. In addition, the results show that the illiter a te participant s are able to perceive and process phonological length, albeit less well than the literate subjects, when no semantic interference is present . In conclusion, the present results confirm and extend the finding that illiterate subjects are biased towards semantic-conceptual-pragmatic type s of cognitive processing
- Sleep promotes the extraction of grammatical rulesPublication . Nieuwenhuis, Ingrid L. C.; Folia, Vasiliki; Forkstam, Christian; Jensen, Ole; Petersson, Karl MagnusGrammar acquisition is a high level cognitive function that requires the extraction of complex rules. While it has been proposed that offline time might benefit this type of rule extraction, this remains to be tested. Here, we addressed this question using an artificial grammar learning paradigm. During a short-term memory cover task, eighty-one human participants were exposed to letter sequences generated according to an unknown artificial grammar. Following a time delay of 15 min, 12 h (wake or sleep) or 24 h, participants classified novel test sequences as Grammatical or Non-Grammatical. Previous behavioral and functional neuroimaging work has shown that classification can be guided by two distinct underlying processes: (1) the holistic abstraction of the underlying grammar rules and (2) the detection of sequence chunks that appear at varying frequencies during exposure. Here, we show that classification performance improved after sleep. Moreover, this improvement was due to an enhancement of rule abstraction, while the effect of chunk frequency was unaltered by sleep. These findings suggest that sleep plays a critical role in extracting complex structure from separate but related items during integrative memory processing. Our findings stress the importance of alternating periods of learning with sleep in settings in which complex information must be acquired.
- Formal schooling influences two- but not three-dimensional naming skillsPublication . Reis, Alexandra; Magnus Petersson, Karl; Castro-Caldas, A.; Ingvar, MartinThe modulatory influence of literacy on the cognitive system of the human brain has been indicated in behavioral, neuroanatomic, and functional neuroimaging studies. In this study we explored the functional consequences of formal education and the acquisition of an alphabetic written language on two- and three-dimensional visual naming. The results show that illiterate subjects perform significantly worse on immediate naming of two-dimensional representations of common everyday objects compared to literate subjects, both in terms of accuracy and reaction times. In contrast, there was no significant difference when the subjects named the corresponding real objects. The results suggest that formal education and learning to read and to write modulate the cognitive process involved in processing two- but not three-dimensional representations of common everyday objects. Both the results of the reaction time and the error pattern analyses can be interpreted as indicating that the major influence of literacy affects the visual system or the interaction between the visual and the language systems. We suggest that the visual system in a wide sense and/or the interface between the visual and the language system are differently formatted in literate and illiterate subjects. In other words, we hypothesize that the pattern of interactions in the functional-anatomical networks subserving visual naming, that is, the interactions within and between the visual and language processing networks, differ in literate and illiterate subjects. (C) 2001 Elsevier Science.
- When the eyes no longer lead: familiarity and length effects on eye-voice spanPublication . Silva, Susana; Reis, Alexandra; Casaca, Luís; Petersson, Karl Magnus; Faísca, LuísDuring oral reading, the eyes tend to be ahead of the voice (eye-voice span, EVS). It has been hypothesized that the extent to which this happens depends on the automaticity of reading processes, namely on the speed of print-to-sound conversion. We tested whether EVS is affected by another automaticity component - immunity from interference. To that end, we manipulated word familiarity (high-frequency, low-frequency, and pseudowords, PW) and word length as proxies of immunity from interference, and we used linear mixed effects models to measure the effects of both variables on the time interval at which readers do parallel processing by gazing at word N + 1 while not having articulated word N yet (offset EVS). Parallel processing was enhanced by automaticity, as shown by familiarity x length interactions on offset EVS, and it was impeded by lack of automaticity, as shown by the transformation of offset EVS into voice eye span (voice ahead of the offset of the eyes) in PWs. The relation between parallel processing and automaticity was strengthened by the fact that offset EVS predicted reading velocity. Our findings contribute to understand how the offset EVS, an index that is obtained in oral reading, may tap into different components of automaticity that underlie reading ability, oral or silent. In addition, we compared the duration of the offset EVS with the average reference duration of stages in word production, and we saw that the offset EVS may accommodate for more than the articulatory programming stage of word N.
- Distinguishing cause from effect - many deficits associated with developmental dyslexia may be a consequence of reduced and suboptimal reading experiencePublication . Huettig, Falk; Lachmann, Thomas; Reis, Alexandra; Petersson, Karl MagnusThe cause of developmental dyslexia is still unknown despite decades of intense research. Many causal explanations have been proposed, based on the range of impairments displayed by affected individuals. Here we draw attention to the fact that many of these impairments are also shown by illiterate individuals who have not received any or very little reading instruction. We suggest that this fact may not be coincidental and that the performance differences of both illiterates and individuals with dyslexia compared to literate controls are, to a substantial extent, secondary consequences of either reduced or suboptimal reading experience or a combination of both. The search for the primary causes of reading impairments will make progress if the consequences of quantitative and qualitative differences in reading experience are better taken into account and not mistaken for the causes of reading disorders. We close by providing four recommendations for future research.
- 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.
- Component processes subserving rapid automatized naming in dyslexic and non-dyslexic readersPublication . Araújo, Susana; Inácio, Filomena; Francisco, Ana; Faísca, Luís; Petersson, Karl Magnus; Reis, AlexandraThe current study investigated which time components of rapid automatized naming (RAN) predict group differences between dyslexic and non-dyslexic readers (matched for age and reading level), and how these components relate to different reading measures. Subjects performed two RAN tasks (letters and objects), and data were analyzed through a response time analysis. Our results demonstrated that impaired RAN performance in dyslexic readers mainly stem from enhanced inter-item pause times and not from difficulties at the level of post-access motor production (expressed as articulation rates). Moreover, inter-item pause times account for a significant proportion of variance in reading ability in addition to the effect of phonological awareness in the dyslexic group. This suggests that non-phonological factors may lie at the root of the association between RAN inter-item pauses and reading ability. In normal readers, RAN performance was associated with reading ability only at early ages (i.e. in the reading-matched controls), and again it was the RAN inter-item pause times that explain the association.