La grande disponibilité et les propriétés psychostimulantes de la caféine en font l’un des psychostimulants les plus consommés mondialement. Sa capacité à augmenter la vigilance serait reliée à son action antagoniste des récepteurs adénosinergiques. Le vieillissement s'accompagne de changements dans les mécanismes de régulation de la vigilance, y compris le système adénosinergique, qui pourraient moduler les effets de la caféine. Alors que plusieurs études ont investigué les impacts de la caféine sur la vigilance chez une population jeune, peu ont identifié les effets chez une population plus âgée. Deux protocoles expérimentaux pouvant distinguer les effets différentiels de la caféine selon l’âge ont été élaborés. La première étude a évalué les effets de 200 mg de caféine sur la vigilance, comparée à un placebo, chez une population jeune et d’âge moyen lors d’une privation de sommeil de 25 heures. L’augmentation de la vigilance subjective et de la performance psychomotrice suite à l’administration de caféine est comparable dans les deux groupes d’âge. Or, des modifications de la puissance spectrale de certaines bandes de fréquences de l’EEG d’éveil suite à l’administration de la caféine sont spécifiques au groupe d’âge moyen. Une deuxième étude a évalué les effets de 200 mg de caféine sur la vigilance, comparée à un placebo, chez des sujets jeunes et d’âge moyen consommateurs légers de caféine. La caféine n’a pas augmenté la vigilance subjective des consommateurs légers. Par ailleurs, la caféine a augmenté la performance psychomotrice de façon similaire dans les deux groupes d’âge. De plus, on remarque que la caféine induit des modifications de la puissance spectrale sur certaines bandes de fréquences à l’EEG chez le groupe d’âge moyen uniquement. Ces travaux suggèrent tout d’abord que la caféine tend à augmenter la vigilance, peu importe le niveau basal d’alerte. De plus, malgré l’absence d’effet subjectif de la caféine sur la vigilance, les consommateurs légers de caféine montrent des effets sur les mesures objectives de la vigilance. Bien que la caféine augmente la vigilance chez les deux groupes d’âge, la spécificité de certaines modifications relevées à l’EEG suggère une augmentation de la sensibilité à la caféine selon l’âge. Il est possible qu’il existe des changements du système adénosinergique au cours du vieillissement qui sous-tendent les effets différentiels de la caféine au cours du vieillissement. / The availability and psychoactive properties of caffeine make it one of the most widely consumed behaviourally active substances in the world. The capacity of caffeine to increase vigilance relies on its antagonist action on adenosine receptors. Aging is associated with changes in the mechanisms regulating vigilance, possibly through changes in the adenosinergic system which could in turn affect eh influence of caffeine. While extensive research identified the impacts of caffeine on vigilance in young populations, few studies have investigated the effects in an older population. Two experimental protocols which can highlight the differential effects of caffeine according to age were elaborated. The first study estimated the effects of 200 mg of caffeine on vigilance, compared with a placebo, in young and middle-aged subjects during 25 hours of sleep deprivation. Caffeine increased subjective and psychomotor measures similarly in young and middle-aged subjects. However, modifications of the spectral power in some frequencies bands after caffeine ingestion were specific to the middle-aged group. The second study focused on the effects of 200 mg of caffeine on vigilance, compared with a placebo, in young and middle-aged light caffeine consumers. Caffeine did not increase subjective alertness in light consumers but enhanced psychomotor performance similarly in both age groups. Furthermore, caffeine affected waking EEG spectral power in specific frequencies bands in the middle-aged group only. In conclusion, these results suggest that caffeine enhance vigilance when basal level of alertness is either high or low. Furthermore, light consumers show effects of caffeine on subjective vigilance but not on objective measures. In spite of an increase of alertness in both age groups, some modifications found in the waking EEG of middle-aged subjects suggest a differential effect of caffeine depending on age. It is possible to hypothesize that changes in the adenosinergic system occur during aging and these changes could explain our results.

La grande disponibilité et les propriétés psychostimulantes de la caféine en font l’un des psychostimulants les plus consommés mondialement. Sa capacité à augmenter la vigilance serait reliée à son action antagoniste des récepteurs adénosinergiques. Le vieillissement s'accompagne de changements dans les mécanismes de régulation de la vigilance, y compris le système adénosinergique, qui pourraient moduler les effets de la caféine. Alors que plusieurs études ont investigué les impacts de la caféine sur la vigilance chez une population jeune, peu ont identifié les effets chez une population plus âgée. Deux protocoles expérimentaux pouvant distinguer les effets différentiels de la caféine selon l’âge ont été élaborés. La première étude a évalué les effets de 200 mg de caféine sur la vigilance, comparée à un placebo, chez une population jeune et d’âge moyen lors d’une privation de sommeil de 25 heures. L’augmentation de la vigilance subjective et de la performance psychomotrice suite à l’administration de caféine est comparable dans les deux groupes d’âge. Or, des modifications de la puissance spectrale de certaines bandes de fréquences de l’EEG d’éveil suite à l’administration de la caféine sont spécifiques au groupe d’âge moyen. Une deuxième étude a évalué les effets de 200 mg de caféine sur la vigilance, comparée à un placebo, chez des sujets jeunes et d’âge moyen consommateurs légers de caféine. La caféine n’a pas augmenté la vigilance subjective des consommateurs légers. Par ailleurs, la caféine a augmenté la performance psychomotrice de façon similaire dans les deux groupes d’âge. De plus, on remarque que la caféine induit des modifications de la puissance spectrale sur certaines bandes de fréquences à l’EEG chez le groupe d’âge moyen uniquement. Ces travaux suggèrent tout d’abord que la caféine tend à augmenter la vigilance, peu importe le niveau basal d’alerte. De plus, malgré l’absence d’effet subjectif de la caféine sur la vigilance, les consommateurs légers de caféine montrent des effets sur les mesures objectives de la vigilance. Bien que la caféine augmente la vigilance chez les deux groupes d’âge, la spécificité de certaines modifications relevées à l’EEG suggère une augmentation de la sensibilité à la caféine selon l’âge. Il est possible qu’il existe des changements du système adénosinergique au cours du vieillissement qui sous-tendent les effets différentiels de la caféine au cours du vieillissement. / The availability and psychoactive properties of caffeine make it one of the most widely consumed behaviourally active substances in the world. The capacity of caffeine to increase vigilance relies on its antagonist action on adenosine receptors. Aging is associated with changes in the mechanisms regulating vigilance, possibly through changes in the adenosinergic system which could in turn affect eh influence of caffeine. While extensive research identified the impacts of caffeine on vigilance in young populations, few studies have investigated the effects in an older population. Two experimental protocols which can highlight the differential effects of caffeine according to age were elaborated. The first study estimated the effects of 200 mg of caffeine on vigilance, compared with a placebo, in young and middle-aged subjects during 25 hours of sleep deprivation. Caffeine increased subjective and psychomotor measures similarly in young and middle-aged subjects. However, modifications of the spectral power in some frequencies bands after caffeine ingestion were specific to the middle-aged group. The second study focused on the effects of 200 mg of caffeine on vigilance, compared with a placebo, in young and middle-aged light caffeine consumers. Caffeine did not increase subjective alertness in light consumers but enhanced psychomotor performance similarly in both age groups. Furthermore, caffeine affected waking EEG spectral power in specific frequencies bands in the middle-aged group only. In conclusion, these results suggest that caffeine enhance vigilance when basal level of alertness is either high or low. Furthermore, light consumers show effects of caffeine on subjective vigilance but not on objective measures. In spite of an increase of alertness in both age groups, some modifications found in the waking EEG of middle-aged subjects suggest a differential effect of caffeine depending on age. It is possible to hypothesize that changes in the adenosinergic system occur during aging and these changes could explain our results.

Made available in DSpace on 2014-12-17T15:37:01Z (GMT). No. of bitstreams: 1 FranciscaPS_DISSERT.pdf: 2124364 bytes, checksum: fdbee75aadf5fa6b72cf6cdc5f8aa5a8 (MD5) Previous issue date: 2010-10-07 / The sleep patterns of students entering the university, is accompanied by many factors that can lead to changes in sleep habits, such as academic demands, new social opportunities, reduced parental care and irregular teaching schedules. The irregular pattern of sleep-wake cycle is usually accompanied by several daytime consequences, for example, reduced levels of motivation, performance, concentration, alertness and mood as well as increased fatigue and sleepiness.Thus, there are numerous reasons to support the fact that these students may suffer damage in their academic performance. The aim of this study was to evaluate the sleep-wake cycle (SWC) and cognition in medical students with different schemes teaching schedules. One group started classes at 08am, while the other started at 07am. We analyzed the data from 88 volunteers, 39 from each group. However, only those who participated in both stages of the study (n = 78) underwent cognitive testing. For subjective evaluation of the SWC was used questionnaires to check the quality of sleep, chronotype, daytime sleepiness and sleep habits. For objective evaluation was used actigraphy. For cognitive assessment was used the test MoCA (Montreal Cognitive Assessment). The results indicate that the group has class earlier had a greater irregularity of the SWC and a worse performance in cognitive testing. There was a difference between the schedules the week and weekend in the subjective variables, bedtime, wake up and sleep duration in both groups. The objective variables, time in bed showed difference between the schedules the week and weekend to the group started class at 08am and the variables bedtime, get up time, actual sleep time, time in bed and wake bouts in the class at 07am. In the cognitive test, there were differences between the groups in overall score and in the areas of executive function and memory recall. Thus, it is suggested that the class starting time may cause irregularity of the SWC and the irregularity may cause mild cognitive impairment. Moreover, cognitive testing MoCA was sensitive to detect differences among students, although the difference between the schedules is small / O padr?o de sono dos estudantes ao entrarem na universidade, ? acompanhado por muitos fatores que podem levar a mudan?as nos h?bitos de sono, tais como demanda acad?mica, novas oportunidades sociais, diminui??o do cuidado dos pais e hor?rios de aulas irregulares. O padr?o irregular de sono-vig?lia ? usualmente acompanhado por v?rias consequ?ncias diurnas, como diminui??o nos n?veis de motiva??o, desempenho, concentra??o, aten??o e humor, bem como aumento da fatiga e da sonol?ncia. Assim, existem in?meras raz?es para apoiar o fato de que, esses estudantes universit?rios, podem sofrer preju?zos em seu desempenho acad?mico. O objetivo desse estudo foi avaliar o padr?o ciclo sono-vig?lia (CSV) e a cogni??o em estudantes de medicina com diferentes esquemas de hor?rios de aulas. Uma turma iniciava as aulas ?s 08 horas da manh?, enquanto a outra iniciava ?s 07 horas. Para isso contamos com 88 volunt?rios. Por?m, desses, apenas os que participaram das duas etapas no estudo (n=78) realizaram o teste cognitivo. Para a avalia??o subjetiva do CSV foi utilizado question?rios para verificar a (1) qualidade de sono, (2) cronotipo, (3) sonol?ncia diurna e (4) h?bitos de sono. Para avalia??o objetiva foi utilizado o act?metro e para avalia??o cognitiva o teste MoCA (Montreal Cognitive Assessment). Os resultados indicam que a turma que tem aula mais cedo teve uma maior irregularidade do CSV e um pior desempenho no teste cognitivo. Houve diferen?a entre os hor?rios da semana e do fim de semana nas vari?veis subjetivas, hora de deitar, hora de levantar e dura??o do sono, em ambas as turmas. E nas vari?veis objetivas, tempo na cama na turma das 08h e, hora de dormir, hora de acordar, tempo real de sono, tempo na cama e despertares noturnos na turma das 07h. No teste cognitivo, houve diferen?a entre as turmas no escore geral e nos dom?nios de fun??o executiva e evoca??o de mem?ria. Assim, sugere-se que o hor?rio de in?cio das aulas pode provocar irregularidade do CSV e, essa irregularidade pode provocar um d?ficit cognitivo leve. Al?m disso, o teste cognitivo MoCA foi sens?vel para detectar diferen?as entre os estudantes, apesar da diferen?a entre os hor?rios ser pequena

Made available in DSpace on 2014-12-17T14:13:59Z (GMT). No. of bitstreams: 1 JoaoFSP_DISSERT.pdf: 3447270 bytes, checksum: 39c94faa709bc806d9f8e00564df8952 (MD5) Previous issue date: 2012-04-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Although several studies, have shown differences in cognitive performance between men and women, it not yet known whether these differences occur in tasks involving free association of words (WA). Studies across the sleep-wake cycle (SWC) suggest that rapid eye movement sleep (REM) favors semantic flexibility, in comparison with pre-sleep waking (Pre-WK), slow-wave sleep (SWS) and post-sleep waking (Post-WK). The present work has two aims: (1) to evaluate the semantic distances of word pairs produced by AP, comparing men and women, (2) to evaluate semantic distance in word pairs produced by free association across the SWC in young adults of both sexes. To achieve aim (1), we applied a task of WA in 68 adult volunteers during waking (52 women and 16 men). The WA task consisted of writing the first word that came to mind after viewing another word offered as a stimulus (root Word). To achieve aim (2), we performed polysomnography to identify specific stages of the SWC. The experimental subjects were then awakened (if they were asleep) and were immediately given a WA task. The task was administered to 2 groups of 10 subjects each (G1 and G2). G1 subjects were stimulated with the same set of root words after waking from various states of SWC, while G2 subjects received sets of different root words at each state of the SWC. In the absence of a Portuguese corpus suitable for the measurement of semantic distances, the words collected in our experiments were translated to English, and semantically quantified within a systematic and representative corpus of that language (Wordnet). This procedure removed the polysemies typical of Portuguese, but preserved the semantic macrostructure common to both languages. During waking, we found that semantic distances are significantly lower in WA produced by women, in comparison with the distances observed in men. Through the SWC, there were no statistically significant differences in G1. In G2 women, we detected a significant increase of semantic distances upon being awakened from SWS. In contrast, G2 men showed a significant increase in semantic distances upon being awakened from REM. The results of the first experiment are consistent with the notion that women have a more concrete reasoning than men. The results of the second experiment indicate that men awakened from REM present more flexibility in word association than when being awakened from other states. In contrast, women showed more flexible word association after being awakened from SWS, in compared with other states. The results indicate that the cognitive flexibility attributed to different states of the SWC shows gender dependency / Embora diversos estudos demonstrem diferen?as no desempenho cognitivo, entre homens e mulheres, ainda n?o se sabe se essas diferen?as ocorrem em tarefas que envolvam associa??o livre de palavras (AP). Estudos atrav?s do ciclo sono-vig?lia (CSV) sugerem que o sono de movimento r?pido dos olhos (MRO) favore?a a flexibilidade sem?ntica, em compara??o com a vig?lia pr?sono (V-Pr?), o sono de ondas lentas (SOL) e a vig?lia p?s-sono (V-P?s). O presente trabalho teve 2 objetivos: (1) Avaliar as dist?ncias sem?nticas de pares de palavras produzidas por AP, comparando homens e mulheres; (2) Avaliar dist?ncias sem?nticas em palavras produzidas por associa??o livre, atrav?s do CSV em adultos jovens de ambos os sexos. Para alcan?ar o objetivo (1), aplicamos uma tarefa de AP em 68 volunt?rios adultos durante a vig?lia (52 mulheres e 16 homens). A tarefa de AP consistiu em listar por escrito a primeira palavra pensada ap?s visualizar outra palavra oferecida como est?mulo. Para alcan?ar o objetivo (2), realizamos registro polissonogr?fico para identificar fases espec?ficas do CSV. Os sujeitos experimentais foram ent?o despertados (caso estivessem em sono) e foram imediatamente submetidos a uma tarefa de AP. Administrou-se a tarefa de AP a 2 grupos de 10 pessoas cada (G1 e G2). Sujeitos de G1 foram estimulados com o mesmo conjunto de palavras-raiz ap?s despertar dos diversos estados do CSV, enquanto que sujeitos de G2 receberam conjuntos de palavras-raiz diferentes a cada estado do CSV. Na aus?ncia de um corpus em portugu?s adequado para ? mensura??o de distancias sem?nticas, as palavras coletadas foram traduzidas para o idioma ingl?s, e semanticamente quantificadas em um corpus representativo e sistem?tico desse idioma (Wordnet). Esse procedimento retirou as polissemias t?picas do portugu?s, mas preservou a macroestrutura sem?ntica comum ?s duas l?nguas. Na vig?lia, verificamos que as dist?ncias sem?nticas s?o significativamente menores nas AP produzidas por mulheres, em compara??o com as dist?ncias sem?nticas verificadas em AP realizadas por homens. Atrav?s do CSV, n?o foram detectadas diferen?as estatisticamente significativas em G1. Em mulheres de G2, detectamos um aumento significativo das dist?ncias sem?nticas ap?s despertar de SOL. Em contraste, homens de G2 apresentaram um aumento significativo das dist?ncias sem?nticas ap?s despertar de MRO. Os resultados do primeiro experimento s?o compat?veis com a no??o de que as mulheres possuem um racioc?nio mais concreto do que homens. Os resultados do experimento 2 indicam que homens despertados durante o MRO apresentam AP mais flex?veis em compara??o com as AP produzidas ap?s vig?lia ou ap?s despertar de SOL. Mulheres apresentaram resultados distintos, com AP mais flex?vel ap?s despertar de SOL, em compara??o com os outros estados. Os resultados indicam que a flexibilidade cognitiva atribu?da a diferentes estados do CSV apresenta depend?ncia de g?nero