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No / In a visual search experiment, the subject must find a target item hidden in a display of other items, and their performance is measured by their reaction time (RT). Here I look at how visual search reaction times are correlated with past reaction times. Target-absent RTs (i.e. RTs to displays that have no target) are strongly correlated with past target-absent RTs and, treated as a time series, have a 1/f power spectrum. Target-present RTs, on the other hand, are effectively uncorrelated with past RTs. A model for visual search is presented which generates search RTs with this pattern of correlations and power spectra. In the model, search is conducted by matching search items up with "categorizers," which take a certain time to categorize each item as target or distractor; the RT is the sum of categorization times. The categorizers are drawn at random from a pool of active categorizers. After each search, some of the categorizers in the active pool are replaced with categorizers drawn from a larger population of unused categorizers. The categorizers that are not replaced are responsible for the RT correlations and the 1/f power spectrum.

L’intégration de stimulations provenant de modalités sensorielles différentes nous offre des avantages perceptifs tels qu’une meilleure discrimination et une accélération des temps de réponse (TR) face aux évènements environnementaux. Cette thèse a investigué les effets de la position spatiale de stimulations visuelles et tactiles sur le gain de redondance (GR), qui correspond à une réduction du temps de réaction lorsque deux stimulations sont présentées simultanément plutôt qu’isolément. La première étude a comparé le GR lorsque les mêmes stimulations visuotactiles sont présentées dans une tâche de détection et une tâche de discrimination spatiale. Les stimulations étaient présentées unilatéralement dans le même hémichamp ou bilatéralement dans les hémichamps opposés. Dans la tâche de détection, les participants devaient répondre à toutes les stimulations, peu importe leur localisation. Les résultats de cette tâche démontrent que les stimulations unilatérales et bilatérales produisent un GR et une violation du modèle de course indissociables. Dans la tâche de discrimination spatiale où les participants devaient répondre seulement aux stimulations présentées dans l’hémichamp droit, les TR aux stimulations bilatérales étaient moins rapides. Nous n’avons pas observé de différence entre le GR maximal obtenu dans l’une ou l’autre des tâches de cette étude. Nous concluons que lorsque l’information spatiale n’est pas pertinente pour accomplir la tâche, les stimulations unilatérales et bilatérales sont équivalentes. La manipulation de la pertinence de l’information spatiale permet donc d’induire une altération du GR en fonction de la localisation des stimulations. Lors d’une seconde étude, nous avons investigué si la différence entre les gains comportementaux résultants de l’intégration multimodale et intramodale dépend de la configuration spatiale des stimulations. Les résultats montrent que le GR obtenu pour les conditions multimodales surpasse celui obtenu pour les stimulations intramodales. De plus, le GR des conditions multimodales n’est pas influencé par la configuration spatiale des stimulations. À l’opposé, les stimulations intramodales produisent un GR plus important iii lorsque les stimulations sont présentées bilatéralement. Nos résultats suggèrent que l’intégration multimodale et intramodale se distinguent quant au GR qu’ils produisent et quant aux conditions nécessaires à cette amélioration. La troisième étude examine le rôle du corps calleux (CC) dans l’observation du GR obtenu pour les stimulations multimodales et intramodales lorsque celles-ci sont présentées unilatéralement et bilatéralement. Quatre patients ayant une agénésie congénitale du corps calleux (AgCC) et un patient callosotomisé ont été comparés à des individus normaux dans une tâche de détection. Dans l’ensemble, les résultats suggèrent que le CC n’est pas nécessaire pour l’intégration interhémisphérique de stimulations multimodales. Sur la base d’études précédentes démontrant le rôle des collicules supérieurs (CS) dans l’intégration multimodale, nous concluons qu’en l’absence du CC, les bénéfices comportementaux résultants d’un traitement sous-cortical par les CS ne reflètent pas les règles d’intégration observées dans les études neurophysiologiques chez l’animal. / The integration of stimuli from the same or different modalities offers many benefits such as enhanced discrimination and accelerated reaction to objects. This thesis investigates the effects of stimuli’s spatial location on the redundancy gain (RG) obtained with cross-modal and within-modal stimulations. The RG is a decrease in reaction times (RT) when two or more stimuli are presented simultaneously rather than a single stimulation. The first study investigated cross-modal visuo-tactile integration in a single reaction time task and a choice reaction time task. Each unisensory stimulus was presented to either the left or right hemispace, and multisensory stimuli were presented in a unilateral (e.g. visual right/tactile right) or bilateral configuration (e.g. visual right/tactile left). The first task was a simple reaction time (SRT) paradigm where participants had to responded to all stimulations, irrespective of spatial position. Results showed that multisensory gain and coactivation were the same for spatially aligned and misaligned visuotactile stimulations. In the second task, a choice reaction time (CRT) paradigm where participants responded to rightsided stimuli only, bilateral stimuli yielded slower reaction times. No difference in multisensory gain was found between the SRT and CRT tasks for unilateral stimulations. Overall, the results suggest that when spatial information is task-irrelevant, multisensory integration of unilateral and bilateral stimuli is equivalent. However, manipulating task requirements can alter this effect. In the second study, we investigated if the behavioral enhancements resulting from within-modal and cross-modal integration depend on the spatial congruency of the redundant stimuli. Results show that the redundancy gains (RG) obtained from the cross-modal conditions were far greater than those obtained from combinations of two visual or two tactile targets. Moreover, we found that the spatial alignment of the targets did not influence the RG obtained in cross-modal conditions, whereas within-modal stimuli produced a greater RG when the targets where delivered in separate hemispaces. These results suggest that within-modal and cross-modal integration are not only distinguishable by the amount of facilitation they produce, but also by the spatial configuration under which this facilitation occurs. The third study examines the role of the corpus callosum (CC) in mediating the RG observed for unilateral and bilateral cross-modal integration. Using a simple detection task, we tested four congenitally acallosal and one callosotomized individuals. No significant difference between congenitally acallosal individuals and controls were found for unilateral within-modal conditions or for multisensory conditions. Overall, these results demonstrate that the CC in not required to integrate cross-modal information across hemispheres and that intrahemispheric processing is preserved in acallosal individuals. Based on previous studies demonstrating the role of the superior colliculus in multisensory integration, our results suggest that in the absence of the CC, the behavioral benefit resulting from subcortical processing by the superior colliculus does not reflect the neurophysiological constraints of multisensory integration.

Nous avons étudié les effets de la baisse de la vigilance sur les mécanismes de contrôle de l'erreur lors d'une tâche de temps de réaction de choix (TR). Lors de la première expérience, la baisse de vigilance a été obtenue par un éveil prolongé de 26 heures. Dans les expériences deux et trois, on a diminué le niveau de vigilance par voie pharmacologique en choisissant de n'affecter qu'une des voies neurochimiques impliquées dans l'éveil (voie histaminergique puis voie dopaminergique) pour déterminer si les indices du contrôle de l'erreur seraient ou non affectés de la même façon qu'après un éveil prolongé. Si oui, cela supposerait un effet redondant des systèmes neurochimiques impliqués dans l'éveil sur le contrôle de l'erreur, dans le cas contraire, cela supposerait une influence spécifique de ces différents systèmes sur le contrôle de l'erreur. Le contrôle de l'erreur peut être décomposé en contrôle proactif et contrôle réactif. Ce contrôle de l'erreur est dit en ligne s'il opère au cours d'un essai, hors-ligne s'il s'opère d'un essai sur l'autre.La privation de sommeil affecte le contrôle de l'erreur proactif en ligne et le contrôle de l'erreur réactif. La baisse de l'activité histaminergique n'affecte que le contrôle de l'erreur réactif et on n'a pas mis en évidence d'effets de la déplétion dopaminergique sur le contrôle de l'erreur. Les effets observés sur le contrôle de l'erreur par la baisse de vigilance induite par la privation de sommeil n'étaient pas reproduits par la baisse de vigilance induite par les déplétions des activités dopaminergiques et histaminergiques, suggérant des influences spécifiques de ces deux voies sur le contrôle de l'erreur. / To study the impact of a vigilance decrease on error monitoring mechanisms in healthy participants, electromyogram and electroencephalogram were recorded during a choice reaction time task. The aim of experiment one was to decipher which indices of error monitoring at the behavioral and electrophysiological levels, were altered by sleep deprivation. In experiments two and three, decreases in vigilance were obtained through pharmacological treatments. We attempted to selectively inhibit one arousal system (either by acting on the histaminergic or on the dopaminergic pathway), so as to determine whether indices of error monitoring would be affected in the same way than after extended wakefulness. Proactive (implemented before an error execution) and reactive modes (implemented after an error execution) of error monitoring were distinguished. Within each mode, we further distinguished on-line (implemented within-trial) and off-line (between-trials) processes.Proactive off-line monitoring was unaffected by the decrease in vigilance, whether this caused by extended wakefulness, histaminergic depeltion or dopaminergic depletion). Sleep deprivation affected proactive on-line and off-line monitoring and reactive control. Histaminergic depletion affected only reactive control and reactive control seemed insensitive to dopaminergic depletion.As sleep deprivation, both histaminergic and dopaminergic depletion induced decrease in vigilance. However, effects of sleep deprivation on error monitoring were entirely reproduced neither by histaminergic nor by dopaminergic depletion, suggesting specific influences of the corresponding systems on error monitoring.

Author: Anna Šalbabová Title: Influence of acrobatic sports on dynamic postrual stability Objectives: The aim of this study is to evaluate an influence of acrobatic sports on dynamic postural stability with greater focus on vestibular system and reaction time of the subjects and to compare those qualities with non-acrobatic subjects who have no history of acrobatic training. Methods: Assessments were performed on NeuroCom Smart Equi Test device, which is located in laboratory of kinesiology at the UK FTVS. There were 20 subjects divided into 2 groups 10 subject each. One group made of 10 acrobatic athletes, the second group of 10 non- acrobatic subjects with no history of acrobatic training. The age of all subjects ranges from 20 to 34 years. For the testing of dynamic postural stability were used Sensory Organization Test (SOT), Motor Control Test (MCT), Head Shake - Sensory Organization Test (HS-SOT). For assessment of vestibulo-ocular reflex was used Dynamic Visual Acuity Test (DVAT), which cannot be performed without Perception Time Test (PPT). Results: The results have shown significantly better reaction times of acrobatic group in MCT and better results of acrobatic group in Head Shake - SOT in half of the performed tests. SOT and DVAT have shown no significant data. Conclusion: This study...

Objetivo Desenvolver um teste psicofísico apoiado em tecnologia móvel em que o desempenho do participante possa revelar à influência da ingestão de álcool pelas alterações cognitivas e motoras produzidas por essa droga. Método Foram 3 protocolos experimentais preliminares. Protocolo experimental 1: Um total de 11 participantes (6 homens e 5 mulheres, de 30 a 53 anos) executaram um teste de tempo de reação go-no-go a três estímulos (semáforo verde:go, semáforo vermelho: no-go, semáforo amarelo: no-go e um estímulo preparatório: semáforo apagado). Protocolo experimental 2: Um total de 13 participantes (mulheres, de 18 a 37 anos) executaram 3 testes: a) Teste de tempo de reação escolha a três estímulos (semáforo verde, semáforo vermelho, semáforo amarelo) e um estímulo preparatório (semáforo apagado). b) Teste de memória em que a tarefa era a de pressionar um botão informando se a imagem que aparecia na tela era nova e outro botão caso a imagem fosse repetida. c) Teste de associação em que a tarefa era a de associar figuras a um número seguindo uma tabela de comparação. Protocolo experimental 3: Um total de 8 participantes (5 homens e 2 mulheres, de 22 a 42 anos) executaram os mesmos testes aplicados no protocolo experimental 2 com apenas uma diferença em uma das tarefas do teste de tempo de reação escolha. A análise de dados privilegiou a análise dos tempos de reação e o índice de acertos. Resultados Protocolo experimental 1 Os testes pareados, tanto para os tempos de reação (t(5)=0,199, p=0,850), quanto para a quantidade de erros (t(5)=0,675, p=0,529), não apontaram nenhuma diferença significativa entre as condições sem e com álcool. Resultados Protocolo experimental 2 As ANOVAs-MR dos tempos de reação e do número de erros do teste de reação escolha não revelaram diferenças significativas para a condição (F(2,36)=1,175, p=0.315, hp 2 =0.32 e F(2,36)=1.944, p=0.165, respectivamente), para cor de semáforo (F(2,36)=0.289, p>0.5, hp 2 =0.16) e tampouco para interação condição x cor de semáforo (F(2,36)=0,355, p=0.840, hp 2 =0.19). No teste de memória, as ANOVAs-MR não revelaram nenhuma 6 diferença significativa para a condição dos tempos de reação (F(2,36)=0,693, p>0,05, n2 =0,05). No teste de associação uma ANOVA-MR revelou uma diferença significativa nos tempos de reação F(2,36)=4,924, p=0,016, n2=0,291), porém nenhuma diferença foi encontrada para erros absolutos (F(2,36)=0,255, p>0,5, n2=0,090) e erros absolutos (F(2,36)=0,255, p>0.5, n=0,02) para a condição sem álcool e com álcool acima de 0.06 %BAC. Resultados Protocolo experimental 3 No teste de tempo de reação escolha não houve indícios de diferenças significantes para as condições com e sem álcool. Os níveis descritivos encontrados no teste Kruskall-Walis foram 0,309, 0,222 e 0,323 para percentual de acerto, tempo médio de reação verde e vermelho, respectivamente. No teste de memória nenhuma das variáveis de tempo de reação (média, maior e menor) apresentou indícios estatisticamente significantes (p-valores 0,633 0,975 e 0,431, respectivamente), tampouco o padrão e indices descritivos (p=0,238) para a média de acertos e o número de acertos. No teste de associação a variável tempo de resposta apresentou evidências estatisticamente significantes de que os grupos não apresentaram valores médios e medianos iguais entre si (p<0,001), houve evidências de que o grupo de 0 a 0,1 %BAC e maior de 0,1 %BAC eram diferentes entre si (p=0,003). Discussão Parece promissor a realização do teste de associação com um aumento da carga cognitiva afim de poder verificar diferenças mesmo quando o indivíduo consumir pequenas doses de álcool. Considerações Finais Os resultados expostos acima dão margem a otimismo e abrem um amplo horizonte de perspectivas em situações ecológicas da vida real, e não mais nas situações tradicionais e artificiais de laboratório, estendendo o ambiente de experimentação e viabilizando a coleta de grandes conjuntos de dados / Objective To Develop a psychophysical test supported by mobile technology in which the performance of the participant could reveal the influence of alcohol intake by cognitive and motor changes produced by this drug. Method There were 3 preliminary experiments. Experiment 1: A total of 11 participants (6 males and 5 females, 30-53 years) performed a go-no-go reaction time test to three stimuli (green traffic light: go, red trafic light: no-go, yellow trafic light: no-go and a preparatory stimulus: black trafic light). Experiment 2: A total of 13 participants (women, 18-37 years) performed three tests: a) A choice reaction time test to three stimuli (green trafic light, red trafic light, yellow trafic light) and a preparatory stimulus (black trafic light). b) A memory test where the task was to press a button stating that the image that was displayed on the screen was new and another button stating that the image was repeated. c) An association test where the task was to associate figures to a number, following a comparison chart. Experiment 3: A total of 8 participants (5 men and 2 women, 22 to 42 years) performed the same tests applied in experiment number 2 with only one difference in a task of the choice reaction time test. Data analysis focused on standart deviations and coefficients of variation. Results Experiment 1 A paired test for both, reaction times (t (5) = 0.199, p = 0.850) and for the number of errors (t (5) = 0.675, p = 0.529) did not show any significant difference between the conditions with and without alcohol. Results Experiment 2 In the choice reaction time test the ANOVAs 2-MR reaction times and the number of reaction errors revealed no significant differences in both conditions (F (2,36) = 1.175, p = 0.315, HP2 and F = 12:32 (2, 36) = 1.944, p = 0.165, respectively) for color signal (F (2,36) = 0.289, p> 0.5, HP2 = 0:16) and also for condition x color signal (F (2,36) = 0.355, p = 0.840, hp2 = 12:19). In the memory test, the ANOVAs-MR showed no significant differences of the reaction time in all conditions (F (2,36) = 0.693, p> 0.05, n2 = 0.05). In the association test ANOVA-MR revealed a significant difference in 8 reaction times F (2,36) = 4.924, p = 0.016, n 2 = 0.291), but no difference was found for absolute errors (F (2,36) = 0.255, p> 0.5, n2 = 0.090) and absolute errors (F (2,36) = 0.255, p> 0.5, n = 0.02) for the alcohol and alcohol above condition 0.06% BAC. Results Experiment 3 In the choice reaction time test there were no significant evidence of a difference between their position values for the condition with and without alcohol. Descriptive levels found in the Kruskal-Wallis test were 0.309, 0.222 and 0.323 for percentage of correct answers, average reaction time of green and red, respectively. In the memory test, none of the reaction time variables (average, highest and lowest) showed statistically significant evidence (p-value 0.633 0.975 and 0.431, respectively), p-value standard (p = 0.238) for the mean score and the number of hits. In the association test the time variable response presented significant statistically evidence that the groups didnt have mean values equal to each other (p <0.001) there were evidence that the group 0 to 0.1% BAC, and the group larger than 0,1% BAC were different from each other (p = 0.003.) Discussion It sounds promising do to more research with the association test with an increase of the cognitive challange in order to verify differences even when the individual takes use of small doses of alcohol. Conlusion The results presented above give rise to optimism and open up a wide horizon of perspectives on ecological situations of real life, and not just in the traditional and artificial situations of the laboratory, extending the experimentation environment and enabling the collection of large data sets

Introdução: Concomitante ao processo de envelhecimento populacional, estão ocorrendo mudanças climáticas, sendo a principal delas o aquecimento global. O envelhecimento leva a mudanças tanto nos mecanismos de termorregulação quanto no desempenho cognitivo. Embora inúmeros estudos tenham avaliado o efeito do calor sobre a cognição de adultos jovens, este é um tema praticamente inexplorado na população geriátrica. Objetivos: Avaliar o efeito da exposição ao calor sobre o desempenho cognitivo de idosos saudáveis e identificar fatores que expliquem as variações na susceptibilidade ao estresse térmico nesta população. Casuística e Métodos: 68 idosos com bom desempenho físico e cognitivo realizaram uma bateria de testes neuropsicológicos em duas condições ambientais: 24oC (controle) e 32oC (calor). Através de cinco testes selecionados da Bateria Neuropsicológica Automatizada de Testes de Cambridge (CANTAB), foram avaliados diferentes aspectos do desempenho cognitivo com foco principal em memória, atenção e velocidade de processamento. Um escore composto global de desempenho cognitivo foi criado usando a medida mais representativa de cada um desses testes. Antes e após cada uma das sessões de testes, foram aferidos o peso corporal, a temperatura axilar, a temperatura auricular, a frequência cardíaca e a pressão arterial. Por meio da análise de variância para medidas repetidas (ANOVA), verificou-se a interação entre o efeito da temperatura na cognição (avaliada pelo escore composto global) e características sociodemográficas (idade, sexo, educação, cor), frequência de exercício físico e umidade relativa registrada durante o protocolo de exposição ao calor. Adicionalmente, foi também desenvolvido um modelo de regressão linear multivariada a fim de identificar variáveis independentes que explicariam a susceptibilidade ao estresse pelo calor. Resultados: A idade média da amostra foi de 73,28 anos. 42,9% dos indivíduos relataram praticar atividade física quatro ou mais vezes por semana. As temperaturas auriculares e axilares aumentaram significativamente após a exposição ao calor, sendo que as diferenças médias encontradas foram de 0,55 e 0,43oC respectivamente. Não foram observadas diferenças significativas entre quaisquer medidas individuais de desempenho ou no escore composto global quando comparamos o desempenho cognitivo sob as duas temperaturas experimentais. Na análise de interação, somente os níveis de umidade registrados durante o protocolo de exposição ao calor e a frequência da prática de exercícios modificaram significativamente o efeito da temperatura sobre o desempenho cognitivo. Os sujeitos expostos a maior umidade relativa do ar no protocolo de calor e os voluntários menos ativos apresentaram piora no desempenho cognitivo na sessão a 32oC. Estes achados foram confirmados num modelo de regressão linear totalmente ajustado. Conclusão: A análise principal mostrou que o desempenho cognitivo de idosos com boa funcionalidade não sofreu efeito deletério da exposição ao calor. No entanto, os voluntários expostos ao calor mais úmido e aqueles que relataram menor frequência de exercício físico apresentaram pior desempenho na sessão de calor que na de controle. As variáveis sócio-demográficas como idade, gênero, escolaridade e cor não tiveram influência na susceptibilidade ao estresse térmico / Introduction: Concomitantly to the process of population aging, major climate changes are taking place, among which global warming is regarded as the most important. Aging leads to changes in temperature control mechanisms and is associated with a subtle and progressive decline in cognitive functions. Although a great deal of studies have evaluated the effect of heat on the cognitive performance of young adults, to the best of our knowledge, no studies have directly investigated the effects of warm environments on the cognitive functioning of older adults. Objectives: To evaluate the effect of heat exposure on the cognitive performance of healthy older adults and to identify factors that would explain variations in susceptibility to heat stress in that population. Methods: 68 older adults with both good physical and cognitive performance were requested to take a series of neuropsychological tests under two environmental conditions: at 24oC and 32oC. Five tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB) were administered to measure different aspects of cognitive functioning while focusing on memory, attention and processing speed. A global composite score of cognitive performance was created, using the most representative measures of each one of those five tests. Before and after each session, measures of auxiliary temperature, tympanic temperature, blood pressure, heart rate, and body weight were obtained. Interaction analysis was carried out using repeated measures analysis of variance (ANOVA) in order to check whether the effect of temperature on cognition, assessed by the global composite score, was modified by sociodemographic characteristics (age, gender, education, race), frequency of physical activity or relative humidity registered during the heat protocol. In addition, a multiple linear regression model has been fitted to identify independent variables that would explain susceptibility to heat stress Results: The mean age of the sample was 73.28 years and 42.9% of the participants reported performing physical activities at least four times a week. Tympanic and auxiliary temperatures increased significantly after the heat exposure with increases of 0.55 and 0.43oC, respectively. No significant differences were observed among any individual measures or the composite score, when comparing the cognitive performance under the two experimental temperatures. In the interaction analysis, only the humidity levels during the heat exposure protocol and the frequency of physical activities significantly modified the effects of temperature on cognitive performance. Participants exposed to higher relative air humidity during the heat protocol and the less active ones have presented worse cognitive performance in the session at 32oC. Those findings have been confirmed by a totally adjusted linear regression model. Conclusion: The main analysis has shown that the cognitive performance of older healthy adults has not had deleterious effect of heat exposure. Nevertheless, the volunteers exposed to more humid heat and those who have reported lower frequency of physical exercises have shown worse performance during the heat session than in the control session. The sociodemographic variables such as age, gender, education and race have not had any influence over susceptibility to heat stress

La mémoire de reconnaissance visuelle (MRV) est atteinte précocement dans la maladie d'Alzheimer (MA). Or, elle reposerait sur deux processus : la familiarité (simple sentiment d'avoir déjà rencontré un item) et la recollection (récupération de détails associés à l'item lors de son encodage). Si la recollection est clairement atteinte au début de la MA, les résultats concernant la familiarité sont à ce jour contradictoires. Supposée plus rapide que la recollection, la familiarité devrait pouvoir être évaluée directement par une approche temporelle. Son atteinte dans la MA pourrait alors être mieux comprise.Pour tester ces hypthèses, la procédure comportementale SAB (Speed and Accuracy Boosting) a été créée. Permettant d'étudier les propriétés de la MRV (sa vitesse-limite, Articles 1 et 2, ou sa nature « bottom-up », Article 3), ainsi que l'hypothèse que la familiarité est plus rapide que la recollection, cette méthode s'est montrée évaluer majoritairement la familiarité (Article 1). Chez des patients à risque de MA, une dissociation inattendue au sein de la familiarité a alors pu être révélée, avec une atteinte des signaux tardifs de familiarité (utilisés lors d'un jugement classique), mais une préservation des premiers signaux (supportant la détection rapide évaluée en SAB) (Article 4).En outre, la segmentation manuelle d'images IRM du lobe temporal interne (premières régions cérébrales touchées dans la MA, et clées pour la MRV) a été appliquée à la problématique connexe de l'effet de l'âge au début de la MA (Article 5).Indépendamment, ces méthodes ont permis de mieux comprendre la MRV et son atteinte au début de la MA ; leur combinaison s'annonce très prometteuse. / Visual recognition memory (VRM) is impaired early in Alzheimer's Disease (AD), but would rely on two processes : familiarity (mere feeling that an item has been seen previously) and recollection (retrieval of details associated to the item at encoding). If recollection is clearly impaired in early AD, results concerning familiarity remain contradictory. Supposed to be faster than recollection, familiarity should be better understood using a temporal approach. Its possible impairment in AD could then be better understood.In order to test this, a behavioural procedure was designed: the SAB (Speed and Accuracy Boosting). Revealing different properties of VRM (its speed-limit, Articles 1 and 2; its « bottom-up » nature, Article 3) and some of its processes (familiarity appeares indeed faster than recollection, Article 1), results showed that the SAB procedure was mainly assessing familiarity (Article 1). In patients at risk of AD, an unexpected dissociation within familiarity processes was evidenced, with an impairment of late signals of familiarity (as used for classical judgements), but a preservation of the first signals (supporting fast detection assessed with the SAB) (Article 4).Last, manual segmentation of MRI images of the medial temporal lobe (first cerebral regions affected in AD, known for their key role in VRM) was also used to assess age effect at the early stage of AD (Article 5).Independently, both methods allowed understanding better the VRM and its impairment in early AD; their combination appears very promising.

Das aktuelle Modell zur Pathophysiologie der Zwangserkrankung (OCD) geht von fronto-striatalen Dysfunktionen aus. Damit werden Beeinträchtigungen im prozeduralen Lernen, das anhand der Serial Reaction Time Task (SRTT) erfasst werden kann, in Verbindung gebracht. Die Befunde zu Defiziten von OCD-Patienten in der SRTT sind widersprüchlich, was auf Unterschiede im methodischen Vorgehen sowie die zusätzliche Auslastung des Arbeitsgedächtnisses durch die Vorgabe einer Gedächtnisaufgabe zurückgeführt wird. Weiterhin ist unklar, ob die vermutete fronto-striatale Dysfunktion und die Defizite im prozeduralen Lernen kennzeichnend für OCD sind oder auch bei anderen Störungsbildern auftreten. Die prozedurale Lernleistung von OCD-Patienten wurde mit der Lernleistung von gesunden Probanden, Patienten mit einer Angststörung und Patienten mit einer Depression verglichen. Weiterhin wurde die prozedurale Lernleistung unter der Vorgabe der SRTT alleine (single-task) und bei gleichzeitiger Vorgabe einer Gedächtnisaufgabe (dual-task) untersucht. OCD-Patienten zeigten im Vergleich zu gesunden Probanden Defizite im prozeduralen Lernen – sowohl unter der single-task als auch unter der dual-task Bedingung. Im Vergleich zu Patienten mit einer Angststörung zeigte sich lediglich in der dual-task Bedingung eine tendenzielle Beeinträchtigung der OCD-Patienten. Keine Unterschiede ergaben sich in der prozeduralen Lernleistung zwischen OCD-Patienten und Patienten mit einer Depression. Die stärkste Beeinträchtigung der prozeduralen Lernleistung in den verschiedenen Symptomdimensionen (Kontrolle, Waschen, Symmetrie, Horten) der OCD zeigte sich in der Dimension Horten. Außerdem waren die Defizite im prozeduralen Lernen stärker bei Patienten mit einem früheren Beginn der Zwangsstörung ausgeprägt. Die Befunde stehen im Einklang mit bisherigen Ergebnissen, wonach bei OCD eine Beeinträchtigung im prozeduralen Lernen vorliegt, was für die Annahme einer fronto-striatalen Dysfunktion bei OCD spricht. / Obsessive-compulsive disorder (OCD) is seen as a disease that implicates fronto-striatal dysfunctions. These dysfunctions are hypothesized to be related to neuropsychological deficits. One of the putative deficits regards procedural learning, which can be assessed by using the serial reaction time task (SRTT). So far, the results regarding procedural learning in OCD patients are inconsistent, which is attributed to differences in methods, like the implementation of a secondary task (dual-task condition) using a concurrent working memory load. Moreover, it is still uncertain whether the fronto-striatal dysfunctions and the deficits in procedural learning are specific to OCD or if they can also be found in other mental illnesses. Procedural learning performance as measured with the SRTT was compared in OCD patients, healthy subjects, patients with anxiety disorder and depression. Additionally, procedural learning was examined under single- (SRTT) and dual-task (SRTT plus a secondary task) conditions. In comparison with healthy subjects, procedural learning was impaired in OCD patients – both in the single- and in the dual-task condition. Yet in the dual task condition, procedural learning was diminished in both groups. Compared to patients with anxiety disorder, OCD patients were impaired in procedural learning only in the dual-task condition, while there was no difference between OCD and depression in procedural learning. Regarding the different symptom dimensions of OCD (checking, washing, symmetry, hoarding), patients high on the dimension hoarding exhibited the most distinct impairment. Moreover, deficits in procedural learning were more pronounced in OCD patients with an earlier age at illness onset. The results confirm previous findings and add supportive evidence for performance deficits in procedural learning and the fronto-striatal dysfunction model of OCD.