No description available.

There is a clearly established division of functional processing between left and right hemispheres of the brain, with the pattern showing robust consistency across individuals. The finding of functional differences between the hemispheres of the brain raises two important questions: First, what mechanisms gave rise to the lateralized biases in processing function? Second, what are the consequences of functional asymmetry of cognitive processing in the human brain on our everyday behaviour? Examining the mechanisms that give rise to cerebral lateralization, Experiments 1 and 2 tested the assumption that there is a causal relationship in the degree and direction of lateralization between left- and right-hemisphere dominant tasks. In experiment 1, this relationship between left-hemisphere processing of speech sounds and right-hemisphere processing of emotional vocalizations was examined using dichotic listening tasks. An overall complementary pattern of lateralization was observed across participants, but no significant relationship was found for degree of lateralization of speech and emotional vocalization processing within individuals. These results support the view that functions in the left and right hemispheres are independently lateralized. In Experiment 2 we examined the relationship pattern in degree of lateralization between linguistic processing and melody recognition using dichotic-listening tasks. The expected left-hemisphere advantage was observed for the linguistic processing task, but the expected right-hemisphere advantage was not observed for the melody recognition task, precluding an informative assessment of complementarity between the two tasks. The division of processing between the two hemispheres of the brain has been shown to result in lateralized performance advantages and behavioural biases. Examining these consequences of lateralization, Experiments 3 through 6 explored the influence of lateral biases on everyday behaviour. Experiments 3 and 4 examined the influence of asymmetries in facial attractiveness on posing biases. Despite evidence suggesting that the right side of the face is found to be more attractive, professional modeling photographs examined in Experiment 3 revealed a leftward posing bias suggesting that asymmetries in facial attractiveness are not dominant in influencing posing behaviour, even when the purpose of the image is to highlight attractiveness. Experiment 4 controlled for image selection biases by examining posing behaviour directly and revealed a rightward posing bias when participants were asked to emphasize their attractiveness. Experiments 5 and 6 examined the influence of lateralized cognitive processing demands on seating preferences. Experiment 5 investigated the real-world seating patterns of theatre patrons during actual film screenings. It was found that, when processing expectations relied on right-hemisphere dominant processes, such as emotional, facial, or visuospatial processing, people were more likely to choose a seat to the right side of the room. Experiment 6 was designed to test two competing theories that have attempted to explain seating biases: one posits that expectation of processing demand drives the bias; the other posits that basic motor asymmetries drive the bias. Through naturalistic observation, I recorded classroom-seating choices of university students using photographs. When processing expectations relied on left-hemisphere dominant processes, such as linguistic processing, people were more likely to choose seats on the left side of the classroom; this finding contrasts the right side bias observed in theatre seating studies, providing evidence that expectation of processing demands influences the seating bias. Addressing the mechanisms that guide the evolution of lateralization, no support for the assumption of a causal relationship between complementary left-and right-lateralized cognitive functions was found. Additionally, examination of asymmetries in everyday behaviours such as seating and posing provide evidence that the lateralization of cognitive functions has a direct influence on human behaviour and interaction with the environment.

Neuromodulation of the immune system has been described to be influenced by hemispheric lateralisation (HL), the stable tendency to relatively utilise one hemisphere or its functions over another. To date there has not been a systematic review of research in this phenomenon conducted, and only one study has examined the effects of HL on the progression of a disease – Human Immunodeficiency Virus (HIV). That research was conducted on a small sample with little control for confounders. The present work sought to compile a systematic review of literature concerning HL and immunity in humans, using effect size analysis. Further, the present work also describes an empirical advancement of this earlier HIV study with stricter control over confounds in a larger sample. The findings corroborated the theory of asymmetrical immune influence by HL via the systematic review showing clear, relatively consistent and strong relationships between left-HL and immunopotentiation. The empirical prospective study extended current knowledge of this relationship in HIV to identify a moderator – HAART treatment. Specifically, left-HL predicted better immunity in HIV-1 patients independent of confounders, with further findings of the same pattern in untreated patients, but not in HAART-treated patients. Further observations were made between HL and HIV-relevant behaviours, again adding to current knowledge. The finding of left-HL being associated with fewer sexual partners in Europeans presents new information of relevance to public health. The combined findings of the present work suggest that left-HL has predictive value in illness (HIV-1) and in general immunity. The present work adds to the existing knowledge new information concerning a moderating factor of the HLimmunity relationship in HIV, and behavioural implications of HL which impact upon HIV disease. Potential explanations for moderation, proposals for neurobiological mechanisms and direction towards future, more rigourous study in the field, both in HIV and immunity, are discussed.

Purpose: The aim of this research was to examine the relationship between stuttering and bilingualism to hemispheric asymmetry for the processing and production of language. Methods: A total of 80 native speakers of German were recruited for the study, ranging in age from 15 to 58 years. Out of those 80 participants, 40 participants were also proficient speakers of English as a second language (L2). The participants were organised into four speaker groups (20 per group) according to language ability and speech status, consisting of monolinguals who stutter (MWS), monolinguals who do not stutter (MWNS), bilinguals who stutter (BWS), and bilinguals who do not stutter (BWNS). Each of the four groups comprised 12 males and 8 females. All participants completed a battery of behavioural assessments measuring functional cerebral hemispheric asymmetry during language processing and production. The behavioural tests included (1) a dichotic listening paradigm, (2) a visual hemifield paradigm, and (3) a dual-task paradigm. Results: Overall, the results showed no significant differences in language lateralisation between participant groups on the three behavioural tests. However group differences were identified in regard to executive functions on the visual hemifield and dual-task paradigms. Both bilingual groups showed significantly faster reaction times and fewer errors than the two monolingual groups on the visual hemifield paradigm. The bilingual groups also performed similarly on the dual-task paradigm, while the MWS group tended to show greater task disruption. No meaningful relationship was found between stuttering severity and the majority of results obtained for the test conditions. However, all four language modalities were found to correlate significantly with results obtained for the visual hemifield and dual-task paradigms, suggesting that performance on these tests increased with higher L2 proficiency. Conclusion: Although no differences in language lateralisation were found, it appears that bilingualism had a greater influence on functional cerebral hemispheric processing than stuttering. A prevailing finding was that bilingualism seems to be able to offset deficits in executive functioning associated with stuttering. Brain reserve and cognitive reserve are thought to have a close interrelationship with the executive control system. Cognitive reserve may have been reflected in the present study, resulting in a bilingual cognitive advantage. Hence, the results of the present study lend support to previous findings implicating the benefits of bilingualism.

This investigation examined the effects of emotion and lateralized presentation of a list of affective words on the learning of that list. This investigation also attempted to assess the separate influences of emotion and arousal on verbal performance. Experiment I was a 2x2 factorial design: two types of pictures from the International Affective Picture System (IAPS), negative or neutral and two gender conditions, male and female. Experiment I was used to verify that the IAPS results in an emotional response. Heart rate (HR) and skin conductance level (SCL) were measured during IAPS presentation. Emotion was assessed after IAPS presentation. Results showed the negative IAPS condition elicited significantly greater increases in SCL and decreases in HR, less self-reported of pleasantness and more self-reported activation than the neutral IAPS condition. Women had significantly lower SCL and higher HR than men; men and women did not differ in reported emotion. Experiment I verified that the negative IAPS elicit changes in SCL and negative emotion in men and women. Experiment II was a 2 x 2 x 2 mixed factorial design: two types of IAPS (negative or neutral), two AAVL conditions (positive and neutral AAVL words or negative and neutral AAVL words) and two presentation conditions (AAVL presented to the left ear (LE) or right ear (RE)). The measure of performance on the AAVL was the number of correct responses. HR and SCL were measured during presentation of the IAPS and of the AAVL. In the negative IAPS condition, performance on negative AAVL was significantly better than that for the positive AAVL; for presentation of the AAVL to the RE, performance on the negative AAVL was significantly better than that for the positive and neutral AAVLs. IAPS condition or ear of presentation alone did not significantly impact on AVVL performance or on SCL and HR during the recitation of the AAVL. Evidence showed that the effect of emotion on performance is a function of mood congruent processing and possibly the allocation of hemispheric resources. / Ph. D.

Visual perception theory distinguishes between two distinct levels of object processing: holistic, based on global shape, and configural, based on local features and/or component parts. Empirical evidence suggests that different cortical regions may support these levels; holistic processing correlates with activation in the lateral occipital-temporal cortex (LOC), whereas configural processes correspond to activation in the parietal lobe, particularly the intraparietal sulcus (IPS). This study combined theories of visual part structure with neuroimaging methods to investigate the relative contribution of holistic and configural processing in an ecologically valid object recognition task. Rather than rely on stimuli specifically designed to evoke holistic or configural processing, this study used photographs of objects selected without a priori assumptions concerning physical part structure. Twenty participants viewed objects at fixation while undergoing fMRI, followed by a behavioral object identification task involving the same objects presented in peripheral vision. Behavioral data were analyzed according to theories of visual crowding to yield an objective estimate of the number of parts perceived within each object. Neuroimaging results revealed increased activation for holistic objects containing fewer parts in the right parietal lobe and superior temporal gyrus and bilaterally in the fusiform gyrus, suggesting a relation between holistic processing areas and object perception. Configural objects with many parts elicited increased activation in the left angular gyrus. This study, to our knowledge, is the first to investigate the cortical visual regions involved when observers engage in holistic and configural processing as a natural part of visual recognition. / Master of Science

The main focus of this investigation was to examine the automaticity of facial expression recognition through valence judgments in a modified photo-word Stroop paradigm. Positive and negative words were superimposed across male and female faces expressing positive (happy) and negative (angry, sad) emotions. Subjects categorized the valence of each stimulus. Gender biases in judgments of expressions (better recognition for male angry and female sad expressions) and the valence hypothesis of hemispheric advantages for emotions (left hemisphere: positive; right hemisphere: negative) were also examined. Four major findings emerged. First, the valence of expressions was processed automatically (robust interference effects). Second, male faces interfered with processing the valence of words. Third, no posers' gender biases were indicated. Finally, the emotionality of facial expressions and words was processed similarly by both hemispheres.

O sinal de entrada na retina é decomposto em termos de frequência espacial (FE), variações periódicas de luminância ao longo do espaço. Existe vasta literatura sobre o processamento de FE no córtex visual primário. No entanto, não se sabe ao certo como esta informação sensorial básica é processada e integrada numa visão de alto nível. Esta tese aborda este tema ao investigar lateralidade cerebral, tempo de processamento e contexto cognitivo em três diferentes seções com objetivos específicos. Estas seções investigaram comportamentalmente visão de alto nível tendo a face humana como estímulo, dado sua relevância biológica e social. Na primeira seção (Theoretical Review), uma revisão apresenta estudos clínicos e neuropsicológicos que mostram áreas cerebrais envolvidas na percepção de faces e como os hemisférios esquerdo e direito realizam um processamento holístico e analítico baseado em informações de FEs. A especialização hemisférica de FE no reconhecimento de faces é então revisada e discutida. Concluiu-se que assimetrias sensoriais podem ser a base para assimetrias cognitivas de alta ordem. Ademais, foi destacado a influência do tempo de processamento. Na segunda seção (Study 1), foi investigado por método psicofísico a lateralidade de baixas e altas FEs no reconhecimento de faces em diferentes tempos de exposição. Faces com filtragem de FE foram apresentadas em campo visual dividido em alta e baixa restrição temporal em duas tarefas: reconhecimento facial (Experimento 1) e reconhecimento do sexo facial (Experimento 2). No Experimento 1, informações faciais de baixas e altas FEs foram mais eficientemente processadas no hemisfério direito e esquerdo, respectivamente, sem efeito do tempo de exposição das faces. Os resultados do Experimento 2 mostraram uma assimetria do hemisfério direito para baixas FEs em baixa restrição temporal. Conclui-se que o processamento de altas e baixas FEs é lateralizado nos hemisférios cerebrais no reconhecimento de faces. No entanto, a contribuição de altas e baixas FEs é dependente da tarefa e do tempo de exposição. Na terceira seção (Study 2) foi investigado qual estratégia temporal, coarse-to-fine (de baixas para altas FEs) ou fine-to-coarse, cada hemisfério cerebral utiliza para integrar informação de FE de faces humanas numa tarefa de categorização facial homem-mulher. Sequências dinâmicas breves coarse-to-fine e fine-to-coarse de faces foram apresentadas no campo visual esquerdo, direito e central. Os resultados do tempo de resposta e do score de eficiência invertida mostraram uma prevalência geral de um processamento coarse-to-fine, independente do campo visual de apresentação. Ainda, os dados da taxa de erro ressaltam o processamento coarse-to-fine realizado pelo hemisfério direito. No geral, esta tese fornece insights sobre assimetria cerebral funcional, integração de alto nível e curso temporal do processamento de FEs, principalmente para aqueles interessados na percepção de faces. Também foi mostrado que operações lateralizadas, tarefa-dependente e coarse-to-fine podem coexistir e interagir no cérebro para processar informação de FE. / Retinal input is decomposed in terms of spatial frequency (SF), i.e., periodic variations of luminance through space. There is extensive literature on the processing of SF in the primary visual cortex. However, it is still unclear how SF information is processed and integrated in high-level vision. This thesis addressed this issue in terms of laterality effects, processing time-course, and the cognitive context in three different sections with specific purposes. These sections behaviorally tackle high-level vision using human faces as stimuli due to their biological and social relevance. In the first section (Theoretical Review) a literature review presented clinical and neurophysiological studies that show brain areas that are involved in face perception and how the right and left hemispheres perform holistic and analytic processing, depending on SF information. The SF hemispheric specialization in face recognition is then reviewed and discussed. Our conclusion is that functional sensorial asymmetries may be the basis for high-level cognitive asymmetries. In addition, we highlighted the role of the processing time. In the second section (Study 1), we psychophysically investigated laterality of low and high SF in face recognition at different exposure times. The SF filtered faces were presented in a divided visual field at high and low temporal constraint in two tasks: face recognition (Experiment 1) and face gender recognition (Experiment 2). In Experiment 1, low and high SF facial information were more efficiently processed in the right and in the left hemisphere, respectively, with no effect of exposure time. In Experiment 2, results showed a right hemisphere asymmetry for low SF faces at low temporal constraint. We concluded that the processing of low and high SF is lateralized in the brain hemispheres for face recognition. However, low and high SF contribution is dependent on the task and the exposure time. In the third section (Study 2), we aimed to investigate which temporal strategy, i.e., coarse-to-fine (from low to high SF) or fine-to-course, each brain hemisphere performs to integrate SF information of human faces in a male-female categorization task. Coarse-to-fine and fine-to-course brief dynamic sequences of faces were presented in the left, right and central visual field. Results of the correct response time and the inverse efficiency score showed an overall advantage of coarse-to-fine processing, irrespective of the visual field of presentation. Data of the error rate also highlights the role of the right hemisphere in the coarse-to-fine processing. All in all, this thesis provided some insights on functional brain asymmetry, high-level integration, and processing time-course of SF information, mainly for those interested in face perception. It was also shown that lateralized, diagnostic-oriented, and coarse-to-fine operations may coexist and interact in the human brain to process SF information.

Over twenty years of research have examined the cognitive consequences of positive affect states, and suggested that positive affect leads to a broadening of cognition. However, this research has primarily examined positive affect that is low in approach motivational intensity (e.g. contentment). In my program of research, I have systematically examined positive affect that varies in approach motivational intensity, and found that positive affect high in approach motivation (e.g. desire) narrow cognition, whereas positive affect low in approach motivation broaden cognition. In this dissertation, I will review past models and present a motivational dimension model of affect that expands understanding of how affective states influence attentional and cognitive breadth. I then review a body of research that has varied the motivational intensity of positive and negative affect and found that affect of low motivational intensity broadens cognitive processes, whereas affect of high motivational intensity narrows cognitive processes. Furthermore, a bi-directional link exists between attentional narrowing and approach motivation, such that a narrowed attentional focus to appetitive stimuli causes greater approach motivation than a broadened attentional focus.

International social movement coalitions are a promising instrument to address systemic problems in a globalizing world. This thesis explores the issue of maintenance of these coalitions by examining the factors that have facilitated or inhibited the maintenance of the Hemispheric Social Alliance as an example. This thesis is based on a qualitative case study; data includes some content analysis but mostly consists of direct interviews. The main finding is that factors such as resources, internal relationships, external conditions and management all affect the maintenance of an international social movement coalition. The thesis argues for increased links between social work and social movement coalitions, and offers insights for social work policy, research and practice.