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In reading, word frequency is commonly regarded as the major bottom-up determinant for the speed of lexical access. Moreover, language processing depends on top-down information, such as the predictability of a word from a previous context. Yet, however, the exact role of top-down predictions in visual word recognition is poorly understood: They may rapidly affect lexical processes, or alternatively, influence only late post-lexical stages. To add evidence about the nature of top-down processes and their relation to bottom-up information in the timeline of word recognition, we examined influences of frequency and predictability on event-related potentials (ERPs) in several sentence reading studies. The results were related to eye movements from natural reading as well as to models of word recognition. As a first and major finding, interactions of frequency and predictability on ERP amplitudes consistently revealed top-down influences on lexical levels of word processing (Chapters 2 and 4). Second, frequency and predictability mediated relations between N400 amplitudes and fixation durations, pointing to their sensitivity to a common stage of word recognition; further, larger N400 amplitudes entailed longer fixation durations on the next word, a result providing evidence for ongoing processing beyond a fixation (Chapter 3). Third, influences of presentation rate on ERP frequency and predictability effects demonstrated that the time available for word processing critically co-determines the course of bottom-up and top-down influences (Chapter 4). Fourth, at a near-normal reading speed, an early predictability effect suggested the rapid comparison of top-down hypotheses with the actual visual input (Chapter 5). The present results are compatible with interactive models of word recognition assuming that early lexical processes depend on the concerted impact of bottom-up and top-down information. We offered a framework that reconciles the findings on a timeline of word recognition taking into account influences of frequency, predictability, and presentation rate (Chapter 4). / Wortfrequenz wird in der Leseforschung als wesentliche Bottom-up Determinante für die Geschwindigkeit des lexikalischen Zugriffs betrachtet. Darüber hinaus spielen Top-down Informationen, wie die kontextbasierte Wortvorhersagbarkeit, in der Sprachverarbeitung eine wichtige Rolle. Bislang ist die exakte Bedeutung von Top-down Vorhersagen in der visuellen Worterkennung jedoch unzureichend verstanden: Es herrscht Uneinigkeit darüber, ob ausschließlich späte post-lexikalische, oder auch frühe lexikalische Verarbeitungsstufen durch Vorhersagbarkeit beeinflusst werden. Um ein besseres Verständnis von Top-down Prozessen und deren Zusammenhänge mit Bottom-up Informationen in der Worterkennung zu gewährleisten, wurden in der vorliegenden Arbeit Einflüsse von Frequenz und Vorhersagbarkeit auf ereigniskorrelierte Potentiale (EKPs) untersucht. Die Ergebnisse aus mehreren Satzlesestudien wurden mit Blickbewegungen beim natürlichen Lesen sowie mit Modellen der Worterkennung in Beziehung gesetzt. Als primärer Befund zeigten sich in EKP Amplituden konsistent Interaktionen zwischen Frequenz und Vorhersagbarkeit. Die Ergebnisse deuten auf Top-down Einflüsse während lexikalischer Wortverarbeitungsstufen hin (Kapitel 2 und 4). Zweitens mediierten Frequenz und Vorhersagbarkeit Zusammenhänge zwischen N400 Amplituden und Fixationsdauern; die Modulation beider abhängigen Maße lässt auf eine gemeinsame Wortverarbeitungsstufe schließen. Desweiteren signalisierten längere Fixationsdauern nach erhöhten N400 Amplituden das Andauern der Wortverarbeitung über die Dauer einer Fixation hinaus (Kapitel 3). Drittens zeigten sich Einflüsse der Präsentationsrate auf Frequenz- und Vorhersagbarkeitseffekte in EKPs. Der Verlauf von Bottom-up und Top-down Prozessen wird demnach entscheidend durch die zur Wortverarbeitung verfügbaren Zeit mitbestimmt (Kapitel 4). Viertens deutete ein früher Vorhersagbarkeitseffekt bei einer leseähnlichen Präsentationsgeschwindigkeit auf den schnellen Abgleich von Top-down Vorhersagen mit dem tatsächlichen visuellen Input hin (Kapitel 5). Die Ergebnisse sind mit interaktiven Modellen der Worterkennung vereinbar, nach welchen Bottom-up und Top-down Informationen gemeinsam frühe lexikalische Verarbeitungsstufen beeinflussen. Unter Berücksichtigung der Effekte von Frequenz, Vorhersagbarkeit und Präsentationsgeschwindigkeit wird ein Modell vorgeschlagen, das die vorliegenden Befunde zusammenführt (Kapitel 4).

Esta dissertação buscou analisar o efeito de priming semântico em uma tarefa de decisão lexical. No estudo 1, comparou-se o efeito de priming semântico entre crianças e universitários em dois SOAs (250ms e 500ms). Os resultados mostraram que no SOA de 250ms, apenas as crianças tiveram efeito de priming semântico. Quando o SOA foi de 500ms, ambos grupos apresentaram efeito de priming semântico, no entanto, este foi maior nas crianças. No estudo 2 foi investigada a relação entre o efeito de priming semântico nas crianças do estudo 1 e as variáveis força de associação e freqüência do alvo. Foram encontradas algumas fracas correlações entre estas variáveis. Conclui-se que variáveis como idade/escolaridade, SOA e força de associação são determinantes no efeito de priming semântico. / The aim of this study was to analyze the semantic priming effect in a lexical decision task. In study 1, the semantic priming effect in third graders and college students was compared. It was used two SOAs, 250ms and 500ms. The results showed that when SOA was 250ms, only third graders had semantic priming effects. When SOA was 500ms, both groups had semantic priming effects; however, the magnitude of it was bigger in children. In study 2, it was investigated the relation between semantic priming effects of third graders and the variables associative strength and frequency. Data demonstrated some weak correlations between these variables. We concluded that variables such age/educational group, SOA and associative strength are related to the semantic priming effect.

Esta dissertação buscou analisar o efeito de priming semântico em uma tarefa de decisão lexical. No estudo 1, comparou-se o efeito de priming semântico entre crianças e universitários em dois SOAs (250ms e 500ms). Os resultados mostraram que no SOA de 250ms, apenas as crianças tiveram efeito de priming semântico. Quando o SOA foi de 500ms, ambos grupos apresentaram efeito de priming semântico, no entanto, este foi maior nas crianças. No estudo 2 foi investigada a relação entre o efeito de priming semântico nas crianças do estudo 1 e as variáveis força de associação e freqüência do alvo. Foram encontradas algumas fracas correlações entre estas variáveis. Conclui-se que variáveis como idade/escolaridade, SOA e força de associação são determinantes no efeito de priming semântico. / The aim of this study was to analyze the semantic priming effect in a lexical decision task. In study 1, the semantic priming effect in third graders and college students was compared. It was used two SOAs, 250ms and 500ms. The results showed that when SOA was 250ms, only third graders had semantic priming effects. When SOA was 500ms, both groups had semantic priming effects; however, the magnitude of it was bigger in children. In study 2, it was investigated the relation between semantic priming effects of third graders and the variables associative strength and frequency. Data demonstrated some weak correlations between these variables. We concluded that variables such age/educational group, SOA and associative strength are related to the semantic priming effect.

Esta dissertação buscou analisar o efeito de priming semântico em uma tarefa de decisão lexical. No estudo 1, comparou-se o efeito de priming semântico entre crianças e universitários em dois SOAs (250ms e 500ms). Os resultados mostraram que no SOA de 250ms, apenas as crianças tiveram efeito de priming semântico. Quando o SOA foi de 500ms, ambos grupos apresentaram efeito de priming semântico, no entanto, este foi maior nas crianças. No estudo 2 foi investigada a relação entre o efeito de priming semântico nas crianças do estudo 1 e as variáveis força de associação e freqüência do alvo. Foram encontradas algumas fracas correlações entre estas variáveis. Conclui-se que variáveis como idade/escolaridade, SOA e força de associação são determinantes no efeito de priming semântico. / The aim of this study was to analyze the semantic priming effect in a lexical decision task. In study 1, the semantic priming effect in third graders and college students was compared. It was used two SOAs, 250ms and 500ms. The results showed that when SOA was 250ms, only third graders had semantic priming effects. When SOA was 500ms, both groups had semantic priming effects; however, the magnitude of it was bigger in children. In study 2, it was investigated the relation between semantic priming effects of third graders and the variables associative strength and frequency. Data demonstrated some weak correlations between these variables. We concluded that variables such age/educational group, SOA and associative strength are related to the semantic priming effect.

In this dissertation the effects of variations in stimulus properties and CTOA, in auditory attention tasks were explored using recently developed approaches to EEG analysis including LIMO. The last experiment was structured using information theory, designing an effective experiment. Four studies were carried out using a number parity decision task, that employed different combinations of cueing Tone (T), Novel (N) and the Goal (G) stimuli. In the first EEG study, contrary to previous findings (Polich 2002, 2007) in control participants, no correlation between the time of a novel condition to the next novel condition and P300 amplitude was found. Therefore single trial across-subject averaging of participants’ data revealed significant correlations (r > .3) of stimulus properties (such as probability, frequency, amplitude and duration) on P300, and even r > .5 was found when N was an environmental sound in schizophrenic patients. In the second EEG study, simultaneously with fMRI recordings, the participants that showed significant behavioural distraction evoked brain activations and differences in both hemispheres (similar to Corbetta, 2002, 2008) while the participants, as a whole, produced significant activations mainly in left cortical and subcortical regions. A context analysis was run in distracted participants contrasting the trials immediately prior to the G trials, resulting in different prefrontal activations, which was consistent with studies of prefrontal control of visual attention (Koechlin 2003, 2007). In the third EEG study, the distractor noise type was manipulated (white vs environmental sounds) as well as presence or absence of scanner background noise in a blocked design. Results showed consistent P300, MMN and RON due to environmental noise. In addition, using time constants found in MEG results (Lu, Williamson & Kaufman, 1992) and adding the CTOA to the analysis, an information theory framework was calculated. After the simulation of the information of the experiment, a saddle indentation in the curve of the information measure based on the states of the incoming signal at around 300 ms CTOA was found. This saddle indentation was evident in more than 60 novel trials. In the fourth study, the CTOA and stimulus properties were manipulated in a parametric experiment. Based on the three studies, reducing complexity if the task (first study), using more than 60 stimuli in the novel conditions (third study). The CTOA randomly varying between 250 ms or 500 ms. Thirty-eight ANCOVA with 2 categorical and 1 continuous regressors were conducted and determined which time and channels elicited reliably signatures (p <.05) in the whole participants at short CTOA. Results revealed differences for the waveforms of current condition by depending on which condition appeared previously as well in terms of frequency and duration in scalp frontal electrodes (such as the second study). These results were interpreted as a consequence of switching between modes of attention and alerting states which resulted in the activation of frontal areas. Moreover, contextual analyses showed that systematic manipulation of stimulus properties allowed the visualization of the relationships between CTOA, executive function and orienting of attention.