Made available in DSpace on 2016-03-22T17:27:34Z (GMT). No. of bitstreams: 1 Tese Marta Tessmann Bandeira.pdf: 1779478 bytes, checksum: 08ef43dde2abf1599e6caa409a3cc035 (MD5) Previous issue date: 2014-12-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The main aim of this dissertation is to investigate the cognitive differences, specially the executive functions: memory, inhibitory control and attention, among monolinguals and bilinguals in two different moments. The first moment happened in 2008 when, for the Master s thesis, the same questions were studied with children in the town of Arroio do Padre, located in the South of Brazil which was colonized by Pomeranians and which localization, with a very distinct geography, makes the access to the most common means of communication more difficult. This fact might help the language preservation that was brought by the immigrants by the end of the XIX century and still in use in this town today. In the present study, the research first done in 2008 is made wider, so the same participants that did the experiments in 2008 were contacted and did the experiments again in 2012, making this a longitudinal study. To complete the data, children and adolescents, monolinguals and bilinguals from Scotland, UK, also participated in this study doing the same experiments, making it possible to observe if bilinguals that have as their mother tongue a not written language, as the Pomeranian, and those who use their first language to do all kinds of tasks including reading and writing, as it happens with the German for the Scottish bilinguals, show any difference in the executive functions investigated in this study. So, the specific aims of this dissertation are briefly to compare children and teenagers, Brazilians and Scottish, monolinguals and bilinguals in tasks involving the general executive control. These tasks are divided in non-verbal (Simon Task) and verbal (Stroop Test). The results found in this dissertation can be divided into two big groups according to the tasks and their specifications. The Simon Task which is a non-verbal task, measures some executive functions, the inhibitory control and attention, in this task the bilingual participants show some advantage. When analyzed the results of the Stroop Test, which is a verbal task, we cannot affirm that there is advantage for the bilinguals, mainly because in this dissertation the language of the bilinguals that participated differ largely: one is written and one is not written. It is known that language and cognition walk together and, according to Bialystok et al. (2009) the advantages found in the tasks of executive functions happen because the mechanism used by the bilinguals inhibit one of his languages and use only the most convenient one are similar to other processes of general executive control / Esta tese tem por objetivo principal investigar as diferenças cognitivas, mais especificamente as funções executivas: memória, controle inibitório e atenção, em monolíngues e bilíngues, em dois momentos diferentes. O primeiro momento aconteceu em 2008 quando, para a Dissertação de Mestrado (2010), estudaram-se estas mesmas questões, com crianças na cidade de Arroio do Padre, situada ao sul do Rio Grande do Sul, cuja colonização é predominantemente pomerana e cuja localização, com geografia e relevo distintos, dificulta o acesso aos meios de comunicação mais comuns, o que facilita a preservação até hoje da língua trazida por seus imigrantes pomeranos no final do século XIX. No presente estudo, ampliando a pesquisa antes empreendida, os mesmos sujeitos participantes dos experimentos em 2008 foram contatados e refizeram-nos em 2012, passando a caracterizar a pesquisa como longitudinal. Alargando o escopo da investigação, crianças e adolescentes monolíngues e bilíngues da Escócia, Reino Unido, também participaram dos mesmos experimentos, possibilitando observar se bilíngues que têm, como sua língua-mãe, uma língua ágrafa, como é o caso do pomerano, e aqueles que usam sua L1 para todos os tipos de tarefas diárias incluindo a escrita e a leitura, como é o caso do alemão para os bilíngues escoceses, apresentam diferenças nas funções executivas aqui investigadas. Assim, os objetivos específicos desta tese resumem-se em comparar crianças e adolescentes, brasileiros e escoceses, monolíngues e bilíngues na realização de tarefas de controle executivo geral. Essas tarefas dividem-se em não verbais (Tarefa de Simon) e verbais (Teste de Stroop). Os resultados encontrados nesta tese devem ser divididos em dois grandes grupos, conforme as tarefas propostas e suas peculiaridades. Pode-se dizer que na tarefa de Simon, que é uma tarefa não-verbal, que mede algumas das funções executivas, o controle inibitório e a atenção, os participantes bilíngues parecem ter vantagens sobre os monolíngues investigados. Já quando analisados os resultados do Teste de Stroop, que é uma tarefa que avalia também as funções executivas, controle inibitório e atenção, entretanto é uma tarefa verbal, não se pode afirmar que há vantagem para os bilíngues, principalmente porque nesta tese as línguas dos participantes do grupo bilíngue são muito diferentes, sendo uma ágrafa e outra não. Sabe-se que linguagem e cognição andam juntas e, de acordo com Bialystok et al. (2009), as vantagens encontradas em tarefas de funções executivas em bilíngues se dão porque os mecanismos utilizados para que o bilíngue iniba uma de suas línguas e use apenas a mais conveniente são semelhantes a outros processamentos do controle executivo em geral

Abstract The aim of this study was to discover attention- and inhibitory control-related differences in the electrical activity of the brain in 6- to 9-year-old children who stutter (CWS) compared to typically developed children (TDC). For studies I and II, the study group consisted of 11 CWS (mean age 8.1 years, age range 6.3–9.5 years; all boys) and 19 fluently speaking children (mean age 8.1 years, age range 5.8–9.6 years; 7 girls). In study III, the participants were twelve boys who stutter (mean age 7.97 years, range 6.3–9.5 years) and 12 typically developed, fluently speaking boys (mean age 8.01 years, range 5.8–9.6 years). The CWS were recruited through local speech therapists and special teachers and newspaper advertisements, while controls were recruited from schools and preschools and among families of department staff and friends. Electroencephalography (EEG) was recorded during a visual Go/Nogo task, which forms a conflict between the pre-potent Go-response and inhibition of response in the Nogo condition, demanding inhibitory control. This EEG data was investigated with conventional event-related potentials (ERP) analysis, potential map and global field power (GFP) analysis and a time-frequency analysis including the periods between tasks. In the ERP analysis, the CWS had a delayed N2 component in the Go condition and a poorly defined P3 component. The potential maps and GFP waveforms confirmed the findings in the Go condition, but also revealed differences in the Nogo condition, described as a prolonged and excessive N2component and an absent P3 component in the CWS. These results indicate problems in the evaluation and classification of the stimulus and the response preparation and inhibition of the response. In the time-frequency analysis, the CWS showed reduced occipital alpha power in the “resting” or preparatory period between visual stimuli, particularly in the Nogo condition. Therefore, the CWS demonstrate reduced inhibition of the visual cortex in the absence of visual stimuli, which is likely related to problems in attentional gating. This newly discovered lack of occipital alpha modulation indicates elementary differences in the regulation of visual information processing in CWS. These findings support the view of stuttering as part of an extensive brain dysfunction involving also attentional and inhibitory networks. / Tiivistelmä Tutkimuksen tavoitteena oli tunnistaa tarkkaavuuteen ja inhibitiokontrolliin liittyviä eroja aivojen sähköisessä toiminnassa 6–9-vuotiailla lapsilla, jotka änkyttävät verrattuna tavanomaisesti kehittyviin lapsiin. Osatöissä I ja II koeryhmässä oli 11 änkyttävää lasta (iän keskiarvo 8.1 vuotta, ikäjakauma 6.3–9.5 vuotta) ja verrokkiryhmässä 19 sujuvasti puhuvaa lasta (keskiarvo 8.1 vuotta, jakauma 5.8–9.6 vuotta; 7 tyttöä). Osatyössä III koeryhmässä oli 12 änkyttävää poikaa (keskiarvo 7.97, jakauma 6.3–9.5 vuotta) ja verrokkiryhmässä 12 sujuvasti puhuvaa poikaa (keskiarvo 8.01 vuotta, jakauma 5.8–9.6 vuotta). Koehenkilöitä haettiin puheterapeuttien ja erityisopettajien välityksellä sekä lehti-ilmoituksilla. Verrokkiryhmän osallistujat rekrytoitiin kouluista, esikouluista sekä henkilökunnan ja ystävien perheiden joukosta. Elektroenkefalografia (EEG) rekisteröitiin visuaalisen Go/Nogo-tehtävän aikana. Tehtävässä ennakoidun Go-vasteen ja Nogo-tilanteessa vaadittavan reaktiosta pidättäytymisen välille syntyvä ristiriita kuormittaa inhibitiokontrollia. EEG-dataa arvioitiin herätevasteiden avulla, tutkimalla jännitekarttojen ja koko pään jännitevaihteluiden eroja sekä käyttämällä aika-taajuusanalyysia, mihin sisältyi myös tehtävien välinen aika. Herätevasteanalyysissä änkyttävillä lapsilla oli viivästynyt N2-vaste Go-tilanteessa ja huonosti erottuva P3-vaste. Jännitekarttojen ja koko pään jännitevaihteluiden perusteella tämä löydös vahvistui, mutta ryhmät erosivat toisistaan myös Nogo-tilanteessa. Änkyttävillä lapsilla N2-vaste oli pidentynyt ja voimakkaampi ja P3-vaste puuttui. Löydökset viittaavat ongelmiin ärsykkeen arvioinnissa ja luokittelussa sekä reaktion valmistelussa ja inhibitiossa. Aika-taajuusanalyysissa änkyttävillä lapsilla oli okkipitaalialueilla merkittävästi vähemmän alfataajuista toimintaa tehtävien välisen ”lepotilan” tai valmistautumisvaiheen aikana erityisesti Nogo-tilanteessa. Änkyttävillä lapsilla näköaivokuoren inhibitio ärsykkeen puuttuessa on näin ollen heikentynyt, mikä viittaa häiriöön tarkkaavuuden suuntaamisessa. Tämä todettu alfatoiminnan säätelyn puuttuminen ilmentää perustavanlaatuisia eroja näköärsykkeen käsittelyssä änkyttävillä lapsilla. Löydökset tukevat näkemystä änkytyksestä osana laaja-alaista aivojen toiminnan häiriötä, joka käsittää todennäköisesti myös tarkkaavuuteen ja inhibitiokontrolliin liittyviä verkostoja.

Submitted by Filipe dos Santos (fsantos@pucsp.br) on 2017-03-17T11:57:31Z No. of bitstreams: 1 Mayra Mika Takatsu.pdf: 2700914 bytes, checksum: 6ada91e713d26ee1a428df1a4249ac21 (MD5) / Made available in DSpace on 2017-03-17T11:57:31Z (GMT). No. of bitstreams: 1 Mayra Mika Takatsu.pdf: 2700914 bytes, checksum: 6ada91e713d26ee1a428df1a4249ac21 (MD5) Previous issue date: 2017-03-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This study investigated the relationship between bilingualism and executive functions: inhibitory control, working memory and cognitive flexibility in monolingual and bilingual children. Bilingualism is a worldwide phenomenon that is constantly growing in Brazil. Previous researches has shown that there is a bilingual advantage when compared to monolingual groups in tasks that measure inhibitory control, working memory and cognitive flexibility. One explanation found in the literature is that this bilingual advantage exists due to the frequent use of two linguistic codes. This daily practice allows bilinguals to inhibit a language that is not being used with a particular interlocutor, consequently obtaining a practise in inhibiting a linguistic code. This practice seems to develop some executive function abilities. This study took place in a religious institution located in the north part of São Paulo city. The participants of this study were 22 children whose age varied from 4 to 6 years old. They were divided in two groups: 11 monolingual Portuguese speakers and 11 bilingual Portuguese and Korean speakers. The materials used were: Teste Stroop para Pré-escolares to measure the inhibitory control ability, Teste Brasileiro de Repetição de Pseudopalavras to measure working memory ability and Dimensional Change Card Sort test to measure the cognitive flexibility ability. Results showed statistically significant advantages to the bilingual group in the working memory (Teste Brasileiro de Repetição de Pseudopalavras) and cognitive flexibility (Dimensional Change Card Sort test) abilities which agree with previous researches. There was a monolingual advantage in the inhibitory control ability (Teste Stroop para Pré-escolares – interference reaction time), but the difference was not statistically significant and this result contradicts previous studies. Future researches with a bigger number of participants and considering the results of the tests presented in this study will help deepen the knowledge about bilingualism and executive functions / O estudo buscou investigar as relações entre o bilinguismo e as funções executivas: controle inibitório, memória de trabalho e flexibilidade cognitiva em crianças pré-escolares monolíngues e bilíngues. O bilinguismo é um fenômeno mundial que apresenta aumento constante no Brasil. Pesquisas anteriores mostraram que existem vantagens para o grupo bilíngue, quando comparado com o grupo monolíngue em tarefas que medem controle inibitório, memória de trabalho e flexibilidade cognitiva. Uma explicação encontrada na literatura é que essa vantagem aparece para os bilíngues devido ao uso frequente de dois códigos linguísticos. Essa prática diária leva o bilíngue a inibir a língua que não está sendo utilizada com determinado interlocutor, obtendo consequentemente uma prática de inibir um código linguístico. Essa prática parece desenvolver algumas habilidades de funções executivas. A pesquisa foi realizada em uma instituição religiosa localizada na zona norte de São Paulo. Participaram deste estudo, 22 crianças de 4 a 6 anos. Foram constituídos dois grupos: 11 crianças monolíngues falantes do português e 11 crianças bilíngues falantes do coreano e português. Foram utilizados, o Teste Stroop para Pré-escolares para medir a habilidade de controle inibitório, o Teste Brasileiro de Repetição de Pseudopalavras Para Crianças para medir a memória de trabalho e o Teste Dimensional Change Card Sort para medir a habilidade de flexibilidade cognitiva. Os resultados mostraram vantagens estatisticamente significativas para o grupo bilíngue nas habilidades de memória de trabalho (Teste Brasileiro de Repetição de Pseudopalavras) e flexibilidade cognitiva (Teste Dimensional Change Card Sort), corroborando com resultados de pesquisas ulteriores. Foi encontrada vantagem para o grupo monolíngue na habilidade de controle inibitório (Teste Stroop para Pré-escolares – TR de interferência), mas a diferença não foi estatisticamente significativa e contradiz resultados de pesquisas anteriores. Futuras pesquisas com uma amostra maior e que considerem os resultados dos testes apresentados neste estudo auxiliarão no aprofundamento sobre o bilinguismo e as funções executivas

O uso problemático de substâncias psicoativas (SPA) tem aumentado significativamente nos últimos anos. Os Transtornos Relacionados a Substâncias (TRS) têm sido associados a uma série de prejuízos cognitivos e comportamentais, dentre os quais destacam-se as disfunções executivas e os déficits envolvendo o controle dos impulsos. A presente tese teve como objetivo investigar as funções executivas, o controle inibitório e a agressividade em indivíduos com Transtornos por uso de álcool e crack. O propósito desta pesquisa foi o de investigar a cognição e o comportamento em amostras distintas de dependentes, visto que são poucos os estudos nessa área enfocando os perfis de déficits cognitivos e comportamentais de acordo com a droga de abuso. Essa tese é composta por um estudo de revisão da literatura e dois estudos empíricos. Foram avaliados 67 homens, com idades entre 18 - 65 anos, divididos em quarto grupos: dependentes de álcool, dependentes de crack, dependentes de álcool + crack e grupo controle. Os dependentes de álcool e/ou crack encontravam-se em abstinência e estavam internados em um programa de tratamento gratuito e voluntário de um Hospital Geral. O protocolo de pesquisa incluiu medidas psicológicas e neuropsicológicas. Os principais resultados deste estudo indicaram prejuízos das funções executivas e do controle inibitório e níveis mais elevados de agressividade nos grupos de dependentes, quando comparados ao grupo controle, tendo esses índices variado de acordo com a droga de abuso. Entre os indivíduos que faziam uso de álcool esses índices foram mais rebaixados, sugerindo que o consumo dessa substância pode estar associado a um maior comprometimento das habilidades de autorregulação e autocontrole. / The problematic use of psychoactive substances has increased significantly in recent years. The Substance-Related Disorders have been linked to a series of cognitive and behavioral impairments, among which is the executive dysfunction and deficits involving impulse control. This thesis aimed to investigate the executive functions, inhibitory control and aggression in individuals with alcohol and crack disorders. The choice of this theme aimed to investigate cognition and behavior in different dependent samples, since there are few studies in this area focusing on the profiles of cognitive and behavioral deficits according to the drug of abuse. This thesis is composed by a review of the literature study and two empirical studies. They were evaluated 67 men, aged 18 -65 years, divided into four groups: alcohol dependents, crack dependents, alcohol + crack dependents and control group. The alcohol and / or crack dependents were in abstinence and were inpatients in a free and voluntary treatment program of a General Hospital. The research protocol included psychological and neuropsychological measures. The main results of this study indicated losses of executive functions and inhibitory control and higher levels of aggression in dependent groups compared to the control group, and these impairments varied according to the drug of abuse. Alcohol dependents showed decreased performance, suggesting that alcohol consumption may be associated with a decrease of self-regulation and self-control skills.

No que diz respeito ao bilinguismo infantil, é grande o número de investigações que comprovam que o uso diário de duas ou mais línguas leva a um desenvolvimento acentuado de certos processos cognitivos (como a atenção seletiva e o controle inibitório), linguísticos e metalinguísticos em comparação com crianças monolíngues de mesma faixa etária (BIALYSTOK, 2001, 2005, 2006, dentre outros). Entretanto, assume-se que tais vantagens são evidentes apenas quando se trata de crianças bilíngues nativas ou com proficiência avançada nas duas línguas faladas. Nesse contexto se insere o presente estudo, que se propôs a investigar os efeitos cognitivos do bilinguismo no desenvolvimento do controle inibitório em um grupo de crianças que estudam em um contexto de escolaridade bilíngue, ou seja, crianças cuja segunda língua é aprendida e vivenciada exclusivamente em contexto escolar, em comparação com bilíngues que aprenderam a segunda língua em contexto familiar ou na comunidade em que vivem, população normalmente testada em experimentos desse tipo. Para isso, foram testadas 174 crianças entre 9 e 12 anos, sendo 75 oriundas de contexto escolar bilíngue (português/inglês), 57 de contexto familiar bilíngue (português/hunsrückisch) e 42 monolíngues do português. Duas tarefas que avaliam controle inibitório foram utilizadas: a Tarefa Simon de flechas e a Tarefa Stroop. Os resultados sugerem que as crianças que estudam em contexto escolar bilíngue, que são expostas e empregam a segunda língua diariamente, embora somente na escola, também parecem se beneficiar de uma experiência bilíngue. / Recent research on childhood bilingualism has indicated that the daily use of two or more languages sharpens the development of certain cognitive processes, such as selective attention and inhibitory control, as well as linguistic and metalinguistic processes, in bilingual children when compared to monolingual children of the same age (BIALYSTOK, 2001, 2005, 2006, amongst others). However, this advantage has only been observed with native bilingual children, or children with very high proficiency in both languages. To fill this gap, the present study aimed to investigate the effect of bilingualism on inhibitory control in bilingual children who experience bilingualism (or second language learning) exclusively in a school context, compared to the usual sample of bilingual children who experience bilingualism at home or in the community. Thus, 174 children of ages 9 to 12 from three different linguistic groups (75 school bilinguals; 57 home bilinguals and 42 monolinguals) participated in the study. Children completed both the Simon Arrows and the Stroop Tasks to assess their inhibitory control with both non-linguistic and linguistic stimuli. Results suggest that bilingual children from a school context, who deal with both languages on a daily basis, although only at school, also show cognitive advantages due to a bilingual experience.

This study examined the effect of an 8-week, progressive exercise intervention on neural responses, specifically N2 amplitude as a measure of inhibitory control, to pictures of food. Healthy women ages 18-44 years were randomized to a morning (AM) exercise group or evening (PM) exercise group. The AM group did moderate-to-vigorous intensity exercise on 4 days per week between 6:30 and 9:30 a.m. while the PM group had the identical volume of exercise between 6:30 and 9:30 p.m. Neural responses, eating behaviors, cardiovascular fitness outcomes, and body weight/composition were measured at baseline and after the 8-week intervention. The N2 amplitude in response to pictures of high- and low-calorie foods was assessed using electroencephalography during a go/no-go task. Dietary restraint, emotional eating, and external eating were assessed using the Dutch Eating Behavior Questionnaire. VO2peak, HRmax, and time to completion were measured during a maximal treadmill test. Body weight was measured on a digital scale, and body composition was measured using dual-energy x-ray absorptiometry. There was not a significant task (go, no-go) × group (AM, PM) × period (baseline, 8 weeks) interaction (F = 0.18; p = 0.677), but there was a main effect of exercise over 8 weeks (F = 6.26; p = 0.017) with increased N2 amplitude following the intervention. There was not a significant interaction as a function of picture type (high-calorie, low-calorie), task, group, and period (F = 0.52; p = 0.478). Changes in body weight and neural outcomes were not significantly associated with changes in eating behaviors for either group (ps < 0.05). There was a significant group × period interaction for body weight (F = 4.90; p = 0.032). Body weight increased by 0.79 ± 1.16 kg in the AM group and decreased by 0.21 ± 1.46 kg in the PM group (effect size = 0.77; CI = 0.15-1.35). There was not a significant group × period interaction for body fat percentage, total body fat or fat-free mass (ps < 0.05). When examining the main effect of exercise on cardiovascular fitness outcomes, VO2peak was not different (F = 1.80; p = 0.187), time-to-completion on treadmill increased (F = 6.51; p = 0.014), and HRmax during the treadmill test was significantly lower (F = 5.49; p = 0.025). This study suggests that 8 weeks of exercise training may increase the inhibitory response to pictures of both high- and low-calorie foods. However, time of day of exercise did not influence this response. Eight weeks of exercise training did not change self-reported dietary restraint, external eating, or emotional eating, and there was no correlation between these eating behaviors and inhibitory control. However, evening exercise was more beneficial for body weight than morning exercise. Given the novelty of this study and its results, additional studies on the influence of time of day of exercise on weight management are needed.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

The “All-or-None Hypothesis (ANH)” (Diamond, 2005; 2006) was examined, positing that executive systems process information and respond to the environment using global heuristics, versus a more piecemeal approach. 104 adults were tested on two novel paradigms designed to uniquely test the ANH. Working Memory (WM) and Inhibitory Control (IC) demands were manipulated, to test the impact of these task demands. Performance measured by reaction times and accuracy on both paradigms provided some support for the ANH. However, this effect was greatest when participants required ‘executive-type’ inhibition, versus ‘motor-type’ inhibition to suppress a response. Further, increasing the WM load increased the ANH trend, while varying the IC requirements had little effect. To our knowledge this is the first direct test of Diamond’s ANH, and extended its specificity in terms of task demands.

Attention-Deficit / Hyperactivity Disorder (ADHD) is characterized by higher than normal levels of inattention, hyperactivity and impulsivity. Behavioural inhibition is proposed to be a primary deficit in children with ADHD, and is included as a component of a number of models accounting for the core behavioural symptoms of ADHD. Children with ADHD often show deficits in their performance on behavioural inhibition tasks relative to typically developing children of the same age, although inconsistent findings have been observed. Stimulant medication is associated with reduction in the core symptoms of ADHD in the majority of children. The primary goal of this thesis was to examine the effects of stimulant medication on behavioural inhibition in children with ADHD. Furthermore, this thesis sought to determine whether children with ADHD who have, and have not taken stimulant medication differ from normally developing children in terms of behavioural inhibition. In order to achieve these aims, it was necessary to firstly determine which tasks provide the best measures of behavioural inhibition. While many tasks have been used to measure inhibitory control amongst children with ADHD, it was unclear from previous research which tasks measure the same constructs. Study 1 investigated relationships in task performance among seven measures of inhibitory control, including the Stop-Signal task, Go / No-go task, Sustained Attention to Response Task (SART; analogous the not-X Continuous Performance Task), Eriksen Flanker task, Stroop, Opposite Worlds task and Task-Switching task. Significant developmental changes in a variety of cognitive abilities occur across childhood and adolescence. To limit the possibility that developmental changes in task performance would be observed, the age range for children included in the study was restricted to seven to 10 years. Nevertheless, to interpret correlations among inhibition measures from the tasks, it was necessary to determine whether children showed comparable developmental trends in their performance across tasks. Study 1A investigated developmental changes in the performances of the seven tasks purported to measure inhibitory control in normally developing children aged seven to 10 years. The results of this study suggested that the tasks chosen were appropriate for use among this age group, and that there is little change in behavioural inhibition across the seven to 10 years age range. In Study 1B, inhibition measures from each of the tasks were included in an exploratory factor analysis to determine those tasks measuring the same constructs. The results of Study 1B suggested that the Stop-Signal, Go / No-go and SART tasks provided the best measures of the behavioural inhibition construct. Performance on the Eriksen Flanker task was also related to the performance on these tasks, but in a direction contrary to that predicted. The Stroop and Opposite Worlds tasks measured the same construct, which appeared to be interference control. Performance on the Task-Switching task was not related to the performance on any other task, suggesting that this task did not measure behavioural inhibition or interference control. Study 2 investigated the performance of children with ADHD on the three tasks shown to be the best measures of behavioural inhibition in Study 1B (i.e., the Stop-Signal task, Go / No-go task and Sustained Attention to Response task). Children with ADHD were aged from seven to 11 years, and were tested both when they had, and had not taken their regularly prescribed stimulant medication. The performance of children with ADHD on these tasks was compared to that of normally developing children matched in age. The results of Study 2 suggested that stimulant medication leads to significant improvement in behavioral inhibition amongst children with ADHD, such that children with ADHD do not differ from matched controls. However, this effect was not observed across all three tasks. Reasons for this, along with study limitations, and directions for future research are discussed.

Attention-Deficit / Hyperactivity Disorder (ADHD) is characterized by higher than normal levels of inattention, hyperactivity and impulsivity. Behavioural inhibition is proposed to be a primary deficit in children with ADHD, and is included as a component of a number of models accounting for the core behavioural symptoms of ADHD. Children with ADHD often show deficits in their performance on behavioural inhibition tasks relative to typically developing children of the same age, although inconsistent findings have been observed. Stimulant medication is associated with reduction in the core symptoms of ADHD in the majority of children. The primary goal of this thesis was to examine the effects of stimulant medication on behavioural inhibition in children with ADHD. Furthermore, this thesis sought to determine whether children with ADHD who have, and have not taken stimulant medication differ from normally developing children in terms of behavioural inhibition. In order to achieve these aims, it was necessary to firstly determine which tasks provide the best measures of behavioural inhibition. While many tasks have been used to measure inhibitory control amongst children with ADHD, it was unclear from previous research which tasks measure the same constructs. Study 1 investigated relationships in task performance among seven measures of inhibitory control, including the Stop-Signal task, Go / No-go task, Sustained Attention to Response Task (SART; analogous the not-X Continuous Performance Task), Eriksen Flanker task, Stroop, Opposite Worlds task and Task-Switching task. Significant developmental changes in a variety of cognitive abilities occur across childhood and adolescence. To limit the possibility that developmental changes in task performance would be observed, the age range for children included in the study was restricted to seven to 10 years. Nevertheless, to interpret correlations among inhibition measures from the tasks, it was necessary to determine whether children showed comparable developmental trends in their performance across tasks. Study 1A investigated developmental changes in the performances of the seven tasks purported to measure inhibitory control in normally developing children aged seven to 10 years. The results of this study suggested that the tasks chosen were appropriate for use among this age group, and that there is little change in behavioural inhibition across the seven to 10 years age range. In Study 1B, inhibition measures from each of the tasks were included in an exploratory factor analysis to determine those tasks measuring the same constructs. The results of Study 1B suggested that the Stop-Signal, Go / No-go and SART tasks provided the best measures of the behavioural inhibition construct. Performance on the Eriksen Flanker task was also related to the performance on these tasks, but in a direction contrary to that predicted. The Stroop and Opposite Worlds tasks measured the same construct, which appeared to be interference control. Performance on the Task-Switching task was not related to the performance on any other task, suggesting that this task did not measure behavioural inhibition or interference control. Study 2 investigated the performance of children with ADHD on the three tasks shown to be the best measures of behavioural inhibition in Study 1B (i.e., the Stop-Signal task, Go / No-go task and Sustained Attention to Response task). Children with ADHD were aged from seven to 11 years, and were tested both when they had, and had not taken their regularly prescribed stimulant medication. The performance of children with ADHD on these tasks was compared to that of normally developing children matched in age. The results of Study 2 suggested that stimulant medication leads to significant improvement in behavioral inhibition amongst children with ADHD, such that children with ADHD do not differ from matched controls. However, this effect was not observed across all three tasks. Reasons for this, along with study limitations, and directions for future research are discussed.