Teoria integrada da fluência: afinal, o que é fluência?

Abstract

Introduction: Facing the need for a conceptual theory on fluency that cooperates not only with its description but also with the explanation about its nature, this thesis presents the proposition of the Integrated Theory of Fluency, built from the recommendations of Caplan (1987) for the development of theories that integrate language and brain. Objectives: To build a conceptual theory on fluency based on Linguistics, Psycholinguistics, and Neuroscience of Language, based on the development of theoretical and empirical arguments that seek to obtain high explanatory power, and are challenged to launch a credible explanation about nature fluency in parallel to the nature of stuttering, in order to cooperate with the elaboration of an answer to the question: after all, what is fluency? For this, it is proposed to investigate components of the event-related potentials (ERPs) elicited by words of open and closed class, in the four functionally distinct phases of linguistic processing in sentence comprehension (sensory-perceptual, syntactic, semantic and integrative), in young adults with and without stuttering, in order to place the ability of Integrated Fluency Theory to be testable. Methodology: This is a theoretical-experimental, quantitative, cross-sectional and descriptive study, which the first stage consisted in the elaboration of theoretical arguments, and the second one consisted in the elaboration of empirical arguments, based on the analysis of the results on dysfunction in the brain. Then, the hypothesis was raised, since fluency is a linguistic skill, its typical development would be directly related to the optimal processes of identification and access to formal traits, especially the categorical one. While stuttering, being a fluency disorder beginning in childhood, it would be related to difficulties in representing formal traits in the mental lexicon and in accessing them during online computing. Hence, an experiment with a mixed paradigm was performed. 14 stuttering adults and 14 fluent adults, with a mean age of 24.6 years old, participated in a silent sentence reading task, performed concurrently with the recording of the underlying brain electrical activity using the electroencephalography technique. The components N1, N2, P3a, N400, LPC, and N500-800, were analyzed, as well as the judgment of the sentences to the question “Is this a good phrase in Portuguese?”. Results: The word classes caused different ERPs. The findings have failed to refute the hypotheses that have been made. The analysis of brain electrical activity underlying the process of categorical word identification was the main difference between the groups. The patterns of atypicality in those who stutter started in N1 and followed throughout all stages of linguistic processing, as a kind of “cascade effect,” which culminated in less accurate understanding in the judgment of sentence. Conclusion: Would P3a be a possible biomarker for stuttering? Stuttering was shown to be related to the four possible locus that are responsible for triggering a Language Development Disorder - LDD (CORRÊA; AUGUSTO, 2011). This finding contributed to the characterization of stuttering as a fluency disorder that starts in childhood, and fluency as a linguistic skill that develops, in addition to enabling the study of language in other neurodevelopmental disorders. The word classes proved to be a viable and promising exploratory setting for the analysis of cerebral electrical activity underlying the typical and deviant processing of language.