Para avaliar a influencia em curto prazo da reposição dopaminérgica na flutuação da atenção em pacientes com DP, a latência média e o desvio-padrão da latência do tempo de reação simples e com escolha foram estabelecidos em 15 pacientes com DP antes e 90 minutos depois da administração da dose habitual matutina de levodopa e em 15 controles normais. Verificou-se , além de efeitos motores, maior sincronia nas latências de testes de tempo de reação complexos, mas não nos simples, sugerindo efeitos da dopamina em mecanismos atencionais e/ou de controle executivo que envolvam flexibilidade na identificação do estímulo e/ou na escolha da resposta / To evaluate short time effects of dopaminergic medication on fluctuation of attention in PD patients, simple and choice reaction latency and latency standard deviation was determined in 15 PD patients before and 90 min. after usual early morning levodopa dose and in 15 normal controls. Besides motor improvement, improved synchrony on complex but not on simple reaction time tests was observed, suggesting dopamine attention and executive control modulation, probably thru stimulus identification and action selection flexibility

The purpose of the present investigation was to examine whether across-trials inconsistency in reaction time (RT), in addition to level of cognitive performance, is predictive of older adults’ performance on a measure of everyday problem solving through a series of three investigations. A sample of community dwelling non-demented older adults, ranging in age from 62 to 92, completed the Everyday Problems Test (EPT), a measure of everyday problem solving that indexes instrumental activities of daily living (IADLs). Performance on the EPT varied according to age, cognitive status, and education, and was significantly predicted by measures of global cognitive status, cognitive decline, and various basic cognitive abilities (i.e., speed of processing, fluid abilities, episodic memory, crystallized abilities). Both inconsistency and mean latencies on measures of RT were found to be significantly associated with concurrent EPT performance, such that slower and more inconsistent RTs were associated with poorer everyday problem solving abilities. Finally, inconsistency in RT made a unique contribution in predicting performance on the EPT two years later, over and above age, education, and various basic cognitive abilities. Structural equation modeling analyses indicated that the relationship between inconsistency in RT and future EPT performance was mediated by fluid and crystallized abilities. Neither inconsistency nor cognitive functioning were significantly associated with changes in EPT performance across two years. Examination of the relationships between IADL functioning, as assessed through self- and informant-report, and inconsistency and basic cognitive abilities demonstrated that everyday problem solving and measures of IADLs tap into related but distinct constructs. The overall pattern of results obtained lends support to the idea that inconsistency in RT represents a behavioural marker of neurological dysfunction. In addition, the present investigation is the first to suggest a relationship between inconsistency in RT and real-world outcomes, such as everyday problem solving and IADL functioning.

L’objectif de ce travail a été d’analyser les effets d’une préparation motrice sur l’activité des motoneurones (MN). Pour cela, des protocoles expérimentaux combinant l’enregistrement unitaire de l’activité des unités motrices des muscles extenseurs du poignet avec des paradigmes de préparation motrice de nature temporelle ont été utilisés chez l’Homme. L’analyse des caractéristiques de la décharge tonique des MN montre un allongement des intervalles inter-potentiels associé à une diminution de leur variabilité durant la période préparatoire, bien avant que la réponse motrice ne soit déclenchée. Ces changements démontrent clairement l’implication de mécanismes inhibiteurs spinaux au cours de la préparation motrice pouvant s’exercer au travers d’interneurones prémotoneuronaux. Il est montré que les modulations d’activité motoneuronales induites par la préparation motrice ne sont ni spécifiques au muscle effecteur de la réponse motrice ni prédictifs de la performance. Il est proposé que l’inhibition exercée sur les MN pendant la préparation motrice constitue un mécanisme généralisé de frein pour retenir le déclenchement prématuré de la réponse motrice, tandis que la diminution de variabilité dans la décharge serait un phénomène de compensation, permettant de produire des forces stables malgré la désactivation motoneuronale. L’implication du niveau motoneuronal dans la préparation motrice montre qu’une information au préalable influence l’état du système moteur jusqu’à son élément le plus périphérique, supportant ainsi le caractère hautement distribué des processus préparatoires. Ce travail a également conduit à proposer l’utilisation de l’entropie approximative pour l’analyse de l’activité motoneuronale, permettant d’éviter les écueils liés aux méthodes classiques d’analyse tout en respectant l’hypothèse d’un codage neuronal temporel. / The aim of this work was to analyze the effects of motor preparation on motoneuron (MN) activity. For this purpose, recordings of wrist extensor muscles motor unit activity were combined with time motor preparation paradigms in Human. Changes in the MN tonic discharge were found to occur during preparatory period, i.e. well before it is time to act. These changes were a lengthening of the mean inter-spike interval associated with a decrease of its variability. These data clearly demonstrate that spinal inhibitory mechanisms are activated during motor preparation and suggest the involvement of premotoneuronal interneurons. The modulations of motoneuronal activity induced by the motor preparation are neither specific to the agonist muscle involved in the motor response nor predictive of the performance. It is assumed that the inhibition acting on the MN during the motor preparation constitutes a general braking mechanism serving to prevent premature motor response, whereas the decrease of discharge variability would be a compensatory phenomenon, allowing to produce an efficient steady force in spite of lower motoneuronal activation. The involvement of the motoneuronal level in motor preparation demonstrates that advance information may influence the state of the motor system, including even the most peripheral motor neurons in the spinal cord, which supports the idea that motor preparation involves highly distributed functional processes. In addition, this work led us to argue in favor of the approximate entropy analysis as a suitable method for analyzing spike trains, allowing to detect changes in the regularity of the time-ordered inter-spikes intervals.

Reaction times (RTs) are a valuable measure for assessing cognitive processes. However, RTs are susceptible to confounds and therefore variable. Exposure to threat, for example, speeds up or slows down responses. Distinct task types to some extent account for differential effects of threat on RTs. But also do inter-individual differences like trait anxiety. In this functional magnetic resonance imaging (fMRI) study, we investigated whether activation within the amygdala, a brain region closely linked to the processing of threat, may also function as a predictor of RTs, similar to trait anxiety scores. After threat conditioning by means of aversive electric shocks, 45 participants performed a choice RT task during alternating 30 s blocks in the presence of the threat conditioned stimulus [CS+] or of the safe control stimulus [CS-]. Trait anxiety was assessed with the State-Trait Anxiety Inventory and participants were median split into a high- and a low-anxiety subgroup. We tested three hypotheses: (1) RTs will be faster during the exposure to threat compared to the safe condition in individuals with high trait anxiety. (2) The amygdala fMRI signal will be higher in the threat condition compared to the safe condition. (3) Amygdala fMRI signal prior to a RT trial will be correlated with the corresponding RT. We found that, the high-anxious subgroup showed faster responses in the threat condition compared to the safe condition, while the low-anxious subgroup showed no significant difference in RTs in the threat condition compared to the safe condition. Though the fMRI analysis did not reveal an effect of condition on amygdala activity, we found a trial-by-trial correlation between blood-oxygen-level-dependent signal within the right amygdala prior to the CRT task and the subsequent RT. Taken together, the results of this study showed that exposure to threat modulates task performance. This modulation is influenced by personality trait. Additionally and most importantly, activation in the amygdala predicts behavior in a simple task that is performed during the exposure to threat. This finding is in line with “attentional capture by threat”—a model that includes the amygdala as a key brain region for the process that causes the response slowing.

Reaction times (RTs) are a valuable measure for assessing cognitive processes. However, RTs are susceptible to confounds and therefore variable. Exposure to threat, for example, speeds up or slows down responses. Distinct task types to some extent account for differential effects of threat on RTs. But also do inter-individual differences like trait anxiety. In this functional magnetic resonance imaging (fMRI) study, we investigated whether activation within the amygdala, a brain region closely linked to the processing of threat, may also function as a predictor of RTs, similar to trait anxiety scores. After threat conditioning by means of aversive electric shocks, 45 participants performed a choice RT task during alternating 30 s blocks in the presence of the threat conditioned stimulus [CS+] or of the safe control stimulus [CS-]. Trait anxiety was assessed with the State-Trait Anxiety Inventory and participants were median split into a high- and a low-anxiety subgroup. We tested three hypotheses: (1) RTs will be faster during the exposure to threat compared to the safe condition in individuals with high trait anxiety. (2) The amygdala fMRI signal will be higher in the threat condition compared to the safe condition. (3) Amygdala fMRI signal prior to a RT trial will be correlated with the corresponding RT. We found that, the high-anxious subgroup showed faster responses in the threat condition compared to the safe condition, while the low-anxious subgroup showed no significant difference in RTs in the threat condition compared to the safe condition. Though the fMRI analysis did not reveal an effect of condition on amygdala activity, we found a trial-by-trial correlation between blood-oxygen-level-dependent signal within the right amygdala prior to the CRT task and the subsequent RT. Taken together, the results of this study showed that exposure to threat modulates task performance. This modulation is influenced by personality trait. Additionally and most importantly, activation in the amygdala predicts behavior in a simple task that is performed during the exposure to threat. This finding is in line with “attentional capture by threat”—a model that includes the amygdala as a key brain region for the process that causes the response slowing.

Abstract: Many regions of the cortex have been identified to be specifically selective for different features. For example, visually presented stimuli proceed, via both the dorsal “where” and ventral “what” streams, before converging in the frontal cortex for decision making processes. However, several subregions of both streams have been identified that demonstrate selectivity on many semantic dimensions, such as size. Most of the studies examining regions selectively activated in maintenance of semantic size have employed the use of visually presented images. In the present, however, study we provide a review of relevant literature, proposed techniques, and a list of word stimuli that may help elucidate the multivariate neural processing of several semantic dimensions.

This work is a result of the current state of the art and the measurement of drivers' reactions and their behavior through the eyetracker during the passage through pedestrian crossings on which the pedestrian crossed. The subject of the measurement was the assessment of the design of the pedestrian crossing and its subsequent influence on the reactions of drivers and their behavior.

This diploma thesis focuses on drivers of motor vehicles and the usual time they spend by specific objects. The theoretical part of the thesis brings an overview of literature on human perception. The eye-tracker is defined here as the instrument used for scanning the movements of the drivers eyes, here are also named its types and its applications in various fields of life. Finally, this part deals with the advertisements placed alongside roads acting as distractive elements. The experimental part builds upon the collected video recordings and offers an analysis of drivers’ observations of outdoor advertisements that attract their attention, mainly billboards.

The semesters thesis is focused on Measurement of Reaction Time and Attention. Part of this work is a definition of reaction time and factors influencing reaction time. Measuring reaction time in context of the theory of intelligence C-H-C is described together with this theory. There are included related tests, specifically Stroop test, Flanker test, Go/No-go test and N-back test. Next there is mentioned online problematics containing hardware and software delays and diagnostic and measuring of the network. The last part of the work is dedicated to a practical part.

This diploma thesis deals with the control of the situation behind the vehicle. The theoretical part of the thesis summarizes the knowledge about the transport system, the reaction time and the individual phases, including the factors influencing the reaction time and the possible methods of its measurement. Further, there are issues of vision from the vehicle and the rules of safe driving. Explanation is the eyetracking method, the types of these devices, and the methods of visualizing the data obtained from the records. In the analytical part are drawn from data recorded video. There are testing route, testing device, testing vehicle and information about testing drivers. The frequency and length of the individual components of the mirror views were evaluated depending on the selected mirror even without dependence from the data obtained.