Le phénomène de Clignement Attentionnel (Attentional Blink, AB), fait référence à une diminution transitoire du rapport exact d’une deuxième cible (C2) si celle-ci est présentée trop tôt après une première cible (C1) lors d’une présentation visuelle sérielle rapide (rapid serial visual presentation, RSVP), et ce, quand les deux cibles doivent être rapportées. Cette étude a examiné l’existence possible d’asymétries hémisphèriques dans le traitement attentionnel ainsi que l’éventualité que la présentation de cibles à deux hémisphères différents puisse diminuer le AB chez des participants neurologiquement sains et l’abolir dans le cas d’un patient callosotomisé. Pour ce faire, nous avons employé un paradigme modifié du AB dans lequel les cibles pouvaient apparaître dans n’importe quelle de quatre RSVP, une dans chaque quadrant du champ visuel, pour permettre des essais dans lesquels les deux cibles puissent être présentées au même hémisphère et d’autres où chaque cible était présentée à un hémisphère différent. Bien que nous n’ayons trouvé aucune diminution de l’effet AB lors de présentation inter-hémisphérique, dans les deux populations à l’étude, le taux de bonnes réponses globales à la deuxième cible était plus élevé quand les cibles étaient présentées à des hémisphères différents. Nous avons également trouvé un avantage de l’hémisphère gauche chez le patient callosotomisé. / The Attentional Blink (AB) refers to a transient impairment in the accurate report of a second target (T2) if it closely follows the presentation of a first target (T1) in a rapid serial visual presentation (RSVP), when both targets must be reported. This study investigated both the possibility of hemispheric asymmetries of attentional processes as well as the possibility that presenting targets to different hemispheres could diminish the AB in neurologically intact participants and abolish it in the case of a split-brain patient. To do so, a modified AB paradigm was used in which targets could appear in any of four simultaneous RSVP streams, one in each quadrant of the visual field, so as to have trials in which both targets were presented to the same hemispheres and trials in which targets were presented to different hemispheres. Although no evidence of a diminished AB was observed by presenting targets to separate hemispheres, in both neurologically intact individuals and the split-brain patient, overall accuracy was higher when targets were presented to separate hemispheres. A left hemisphere advantage was only observed in the split-brain patient.

The utilisation of navigation systems in cars has given rise to road safety concerns, and the design and functionality of such systems must therefore be adjusted to the users’ needs, since they have to divide their attention between driving and the operation of the navigation system. The study was aimed at finding the optimum system response time (SRT) which would enable a driver to focus as much as possible on the road while attaining an efficient task completion time using an electronic navigational system. The research project consists of two separate experiments and was completed by 10 subjects. Experiment 1 included a temporal reproduction task and a secondary memory task. The subjects had to memorise two symbols and then reproduce six time spans ranging from 1 to 30 s to provide a baseline measurement of their time estimation abilities. Experiment 2 consisted of a simulated automobile driving task. While driving in the simulator the subjects completed a memorising task displayed on a touch screen. The task was presented with seven different system response times (SRTs) ranging from 0 to 30 s. The effects of different SRTs on the eye movement from road to monitor, regarding the duration of fixation and the frequency of change were evaluated. The distribution of gazes to the secondary task was analysed to provide information about the time estimation performance in the driving simulator. Other dependent variables tested were the accuracy of selected items, memory game performance, drive performance and the subjective state of the test person. The results of this study can be employed to find the optimum duration of inter-task delays for in-vehicle technical devices. / Psychology / M.A. (Psychology)

The present study characterized two fiber pathways important for language, the superior longitudinal fasciculus/arcuate fasciculus (SLF/AF) and the frontal aslant tract (FAT), and related these tracts to speech, language, and literacy skill in children five to eight years old. We used Diffusion Tensor Imaging (DTI) to characterize the fiber pathways and administered several language assessments. The FAT was identified for the first time in children. Results showed no age-related change in integrity of the FAT, but did show age-related change in the left (but not right) SLF/AF. Moreover, only the integrity of the right FAT was related to phonology but not audiovisual speech perception, articulation, language, or literacy. Both the left and right SLF/AF related to language measures, specifically receptive and expressive language, and language content. These findings are important for understanding the neurobiology of language in the developing brain, and can be incorporated within contemporary dorsal-ventral-motor models for language.

Conflicts are part of our everyday life and the field of psychology describes how specific personality traits relate to specific conflict styles. However, the question remaining is why these relations exist? Recently, personality neuroscience has begun pinning down the neurobiology of personality traits, providing a deeper understanding of the human behavior. The present thesis utilizes the Five Factor Model (FFM; Costa & McCrae, 1990) of personality to investigate the neurobiology underlying the inverse relation between the specific personality trait of Agreeableness and dominating conflict style (a conflict management style characterized by aggressiveness, authoritarianism and/or need for dominance). Agreeableness overlaps both empathy and aggression which can work as each other’s opposites in explaining conflict behaviors. The goal of the thesis was to investigate whether the inverse relation between Agreeableness and dominating conflict style can be explained by brain regions. Brain regions such as the medial prefrontal cortex and regions involving anterior cingulate appear to be the most prominent neurobiology describing the relation. Serotonin is the neural substance involved in most cortical and subcortical brain structures and it also regulates the suppression of aggression, making it an important substance both within Agreeableness and the preference for dominating conflict style. The thesis will sum up with a discussion including some limitations within the research and further aspects such the consequences of the findings will be discussed.

Our bodies are arguably one of the most intimate things we will ever know. But the comfort of our own physical boundaries can be altered in various ways. In this analysis, we will look at how vision contributes to the sense of owning a body by analysing six abnormal conditions: the rubber hand illusion, phantom limbs, somatoparaphrenia, the body-swap illusion, out-of-body experiences, and heautoscopy. Examinations of these experimental or pathological conditions has granted a greater understanding of body-ownership. It was discovered that vision plays different modulatory roles, being more intricately involved in full-body ownership than in part-body ownership. Vision appears to be highly connected to self-location and first-person perspective, which both are contributing factors in projecting the sense of ownership to an external location. In part-body ownership, however, vision can be overruled by other senses, such as proprioception. Though it is still able to contribute to the illusion of projecting ownership and proprioceptive displacement to a rubber hand.

When portraying a character in a fictional world the actor is faced with many challenges. To circumvent these challenges, he must become congruent with the reality of the fictional world. In order to do so, the actor has to ‘believe’ in the circumstances of the unfolding scene and live ‘in the moment’. These external circumstances act as stimuli which the actor uses to create and consequently ‘believe’ in the environment that the character inhabits. However, the use of green screen technology in special effects limits or eliminates these stimuli and the external circumstances. Green screen is a technique used in film and television that allows the filmmaker to film an actor in combination with a green screen and then replace the ‘green’ with anything the filmmaker requires. This allows for compositing to occur and the filmed reality to be manipulated. However, this technology challenges the actor’s ‘belief’ and behaviour, thus affecting congruence with and the (photo)realism of the created fictional world. In a green screen environment the actor is challenged to imagine, experience and act in line with the circumstances of the fictional world that will replace the green screen, instead of the green environment in which he finds himself. One acting strategy that elicits imagination, action and feeling is Stanislavsky’s notion of the magic if. Accordingly, this dissertation proposes that this strategy can assist the actor in circumventing the challenges that arise when working with green screen technology. Stanislavsky developed his acting principles by observing human behaviour in an attempt to use the mind–body paradigm in circumnavigating the acting moment. The field of cognitive neuroscience has also investigated human behaviour and the mind–body paradigm and recent discoveries have increased understanding of the fields. These discoveries have validated the notion of the magic if and the components it incorporates. Yet, the discoveries surrounding the notion of the magic if and, subsequently, the increased understanding of the concept have not to date been applied to acting with green screen technology. It is therefore hypothesised that, by triangulating the challenges of ‘green screen acting’, the principles of the magic if and the knowledge gained from cognitive neuroscience, an acting strategy can be developed that will assist the actor in the green screen environment and thus create verisimilitude with the fictional world. This hypothesis has led to the theoretical development of explorations that will strengthen the skills the actor needs in order to apply the notion of the magic if; as well as an acting strategy to assist the actor when entering the green screen environment. / Dissertation (MA)--University of Pretoria, 2013. / gm2014 / Drama / Unrestricted

The natural world provides sensory systems with noisy and ambiguous information, which is often transformed into a more stable categorical percept. This thesis aims to investigate the nature of the neural representations in the visual system that support this transformation. To do so, we will employ a behavioural task that requires participants to average several independent sources of perceptual information. This task allows for the dissociation of two theoretically orthogonal sources of decision uncertainty: the mean distance of the perceptual information from a category boundary and the variability of the evidence under consideration. Behaviourally, both decreasing the mean distance to bound of information and increasing information variability are associated with increased errors and prolonged response times. We will present a computational model that can account for the independent behavioural effects of these two sources of uncertainty by assuming that categorical decisions are made on the basis of a probabilistic transformation of perceptual evidence. BOLD measurements demonstrate that these effects of mean and variability are supported by a partially dissociable network of brain regions. Electroencephalography demonstrates the differential influence of mean and variance in the pre- and post-decision period. Furthermore, we show that there is adaptation at the level of the perceptual representation to the information variance. Not only does this show that the visual system must represent information at the summary level, in addition to individual feature-based representation, but it also suggests that the costs associated with this form of perceptual uncertainty can be largely mitigated by the adoption of a more suitable representational range.

Longitudinal developmental fMRI studies just recently began to focus on within-subject reliability using the intraclass coefficient (ICC). It remains largely unclear which degree of reliability can be achieved in developmental studies and whether this depends on the type of task used. Therefore, we aimed to systematically investigate the reliability of three well-classified tasks: an emotional attention, a cognitive control, and an intertemporal choice paradigm. We hypothesized to find higher reliability in the cognitive task than in the emotional or reward-related task. 104 healthy mid-adolescents were scanned at age 14 and again at age 16 within M = 1.8 years using the same paradigms, scanner, and scanning protocols. Overall, we found both variability and stability (i.e. poor to excellent ICCs) depending largely on the region of interest (ROI) and task. Contrary to our hypothesis, whole brain reliability was fair for the cognitive control task but good for the emotional attention and intertemporal choice task. Subcortical ROIs (ventral striatum, amygdala) resulted in lower ICCs than visual ROIs. Current results add to the yet sparse overall ICC literature in both developing samples and adults. This study shows that analyses of stability, i.e. reliability, are helpful benchmarks for longitudinal studies and their implications for adolescent development.

Le paradigme bayésien s'est imposé comme une interprétation mathématique élégante du comportement humain dans des tâches d'inférence. Pourtant, il ne rend pas compte de la présence de sous-optimalité, de variabilité, et de biais systématiques chez les humains. De plus, le cerveau doit mettre à jour ses représentations du monde extérieur, au fil des informations qui lui parviennent, dans des environnements naturels qui changent au cours du temps, et présentent une structure temporelle. Nous étudions la question de l'inférence séquentielle à l'aide d'une expérience, dont les résultats montrent que les humains tirent parti, dans leur inférence, de la structure temporelle des signaux; et que la variabilité des réponses est elle-même fonction du processus d'inférence. Nous étudions 27 modèles sous-optimaux capturant des limitations cognitives à l'optimalité. La variabilité des réponses est reproduite par des modèles qui font une approximation, par échantillonnage durant l'inférence, du posterior, et par des modèles qui, dans leur réponse, échantillonnent le posterior, plutôt que de le maximiser. Les données expérimentales soutiennent plus fortement la première hypothèse, suggérant que le cerveau utilise quelques échantillons pour représenter, par approximation, le posterior bayésien. Enfin, nous étudions les "effets séquentiels", biais qui consistent à former des attentes erronées à propos d'un signal aléatoire. Nous supposons que les sujets infèrent les statistiques du signal, mais cette inférence est sujette à un coût cognitif, menant à des comportements non-triviaux. Considérés dans leur ensemble, nos résultats montrent, dans le cas naturel de l'inférence séquentielle, que des déviations du modèle bayésien optimal permettent de rendre compte de manière satisfaisante de la sous-optimalité, de la variabilité, et des biais systématiques constatés chez l'humain. / In past decades, the Bayesian paradigm has gained traction as an elegant and mathematically principled account of human behavior in inference tasks. Yet this success is tainted by the sub-optimality, variability, and systematic biases in human behavior. Besides, the brain must sequentially update its belief as new information is received, in natural environments that, usually, change over time and present a temporal structure. We investigate, with a task, the question of human online inference. Our data show that humans can make use of subtle aspects of temporal statistics in online inference; and that the magnitude of the variability found in responses itself depends on the inference. We investigate how a broad family of models, capturing deviations from optimality based on cognitive limitations, can account for human behavior. The variability in responses is reproduced by models approximating the posterior through random sampling during inference, and by models that select responses by sampling the posterior instead of maximizing it. Model fitting supports the former scenario and suggests that the brain approximates the Bayesian posterior using a small number of random samples. In a last part of our work, we turn to "sequential effects", biases in which human subjects form erroneous expectations about a random signal. We assume that subjects are inferring the statistics of the signal, but this inference is hindered by a cognitive cost, leading to non-trivial behaviors. Taken together, our results demonstrate, in the ecological case of online inference, how deviations from the Bayesian model, based on cognitive limitations, can account for sub-optimality, variability, and biases in human behavior.

With the increase in survival for children with cancer, part of the focus of current research is aimed towards evaluating how these children are adapting psychosocially. Neurocognitive deficits have been well established. However, there are multiple facets encompassing quality of life, including general mental health, lifestyles and health behaviors, and academic and cognitive functioning. The relationship between neurocognitive and psychosocial functioning has yet to be thoroughly evaluated. The purpose of this study was to investigate the relationship between neurocognitive and psychosocial functioning in survivors of brain tumors and acute lymphoblastic leukemia. Data was collected from existing archival database comprised of patients of the at Cook Children's Medical Center in Texas. The sample consisted of 177 patients between the ages of 3 and 12 who were at least two years post-diagnosis. Measures used included the NEPSY and the Behavioral Assessment for Children. Statistical analyses included a several one-way analysis of variances, an independent samples t-test, a univariate analysis of variance, a hierarchical multiple regression, and odds ratio analyses. Results indicated survivors treated with neurosurgery alone appear to be less at risk for developing behavior problems than other treatment modalities. Also, brain tumor survivors demonstrate more problematic behaviors than survivors of acute lymphoblastic leukemia. Visuospatial functioning, diagnosis, and type of treatment were found to be predictive variables of behavior problems. Attention, and perhaps language, deficits may predispose children to more problems in their behavior. It is concluded that there are other factors affecting behavior in this population that were not accounted for in this analysis. It is recommended for future studies to research the individual clinical scales of the Behavior Assessment System for Children, obtain information from multiple informants, study this relationship longitudinally, and research additional factors that may be influencing the relationship between neurocognitive and psychosocial functioning. This provides evidence of risk factors that should be monitored as the child returns home and to school.