1,720,977 research outputs found
Exploring the antisaccade task in relation to motor and cognitive functions in adults with mild to moderate idiopathic Parkinson’s Disease
No full textParkinson’s Disease (PD) is a neurodegenerative disease characterized by motor impairments including bradykinesia, rest tremor, and postural instability. In addition, motor dysfunction appears in oculomotor abnormalities, specifically saccadic eye movement deficits. It is now recognized that PD extends beyond motor impairments and affects sensory and cognitive domains. PD alters a range of cognitive functions, but particularly affects response inhibition, even early in the disease course. The antisaccade task is an oculomotor paradigm used to evaluate response inhibition and is a sensitive indicator of PD. Antisaccade task performance has been well characterized in PD patients, but it is unclear what factors contribute to these deficits. Here we investigated whether antisaccade performance in mild to moderate PD is related to motor function, executive function, and or general cognitive ability. We evaluated pro- and antisaccade performance in 17 patients and 20 matched controls. Saccade latencies, amplitudes, and error rates were compared between groups, and were correlated to performance on a series of motor (Timed up and Go test) and cognitive tasks (Trail Making Task, Stroop Task, and matrices sub-test of the Kaufman Brief Intelligence Index). Relative to controls, patients showed smaller amplitude prosaccades, and more than double the frequency of errors when executing antisaccades (patients M=21.7% SD= 18.6%; controls M=10.5%, SD=11.43%; p=0.013; d= 0.72). However, patients performed equal to, or better than controls on the battery of motor and cognitive assessments. Our results cautiously suggest that PD patients show deficits in response inhibition despite an absence of cognitive dysfunction on standard neuropsychological tools. With additional investigation, antisaccade task performance has the potential to be a sensitive indicator of early changes in response inhibition in PD, to be used as a tool in compliment with clinical evaluation.Medicine, Faculty ofGraduat
Eye movements, trait impulsivity, and hypomania proneness in healthy young adults
No full textBipolar disorder is defined as a brain disorder characterized by extreme mood fluctuations that result in changes in energy and disability. Enhanced impulsivity is present in episodes of mania or hypomania in bipolar disorder, of particular importance are factors of impulsivity such as inability to predict or anticipate future events. Delineating trait versus state components of impulsivity helps identify risk factors for bipolarity and evaluate disease progression. Eye movements have been used to assess impulse control as well as predictive and anticipatory mechanisms. Here, we use a subsyndromal approach to relate eye movement measures to impulsivity and hypomania proneness in a cohort of young adults not previously diagnosed with a psychiatric disease. We assessed 60 participants (20 males, 40 females) in the antisaccade task, and a smooth pursuit battery that include a sinusoidal pursuit paradigm and a predictive pursuit task. Participants additionally completed the Hypomanic Personality Scale and Barrat Impulsiveness Scale. We found positive relationships of small effect size between mean number of express saccades in antisaccade trials and deceleration after target extinction in predictive pursuit with hypomania proneness. We also show a negative trend of small effect size between initial eye acceleration with hypomania proneness. Given that we tested healthy participants and assessed hypomania proneness, our results might suggest a state-related component of impulsivity. However, all results must be interpreted with caution as none are statistically significant.Medicine, Faculty ofGraduat
Motion processing across spatial and temporal scales for human perception and eye movements
No full textWe live in a dynamic visual environment, which requires perceiving moving objects around us and acting accordingly. However, we do not yet fully understand how visual information informs perception and motor actions. This dissertation examines the perception-action link by testing how motion and expectation signals are processed for perception and for eye movements as an example of human motor action.
I focus on two types of human eye movements triggered by distinct brain mechanisms: ocular torsion, the eyes’ rotation about the line of sight triggered by rotational motion, and smooth pursuit, the eyes’ continuous tracking of translational motion. Torsion is mostly controlled by subcortical brain areas, but might share early-stage cortical processing of sensory signals with perception. In contrast, smooth pursuit is controlled by subcortical and cortical areas and might therefore be more closely linked to perception, sharing both motion and expectation signal processing with perception.
To test the torsion-perception link, I utilized a perceptual illusion induced by visual rotational motion. Results show that torsional velocity correlates with the perceptual illusion, potentially suggesting shared motion processing (Chapter 2.1). However, anticipatory torsion can only be elicited by trial repetition, but not by cognitive cues that induce expectation (Chapter 2.2). These results show that similar visual motion signals might drive reflexive torsion and perception. Expectation signals appear to be less effective in driving torsion.
Probing the pursuit-perception link, I found dissociations between how each system processes motion and expectation signals. When integrating diverse motion signals across space, pursuit was biased to the average motion direction, whereas perception showed no consistent bias (Chapter 3). When investigating the role of expectation, I found that anticipatory pursuit followed the expected direction, whereas perception was biased in the opposite direction (Chapter 4).
Overall, this dissertation reveals that perception and eye movements likely share early-stage motion processing, even for reflexive eye movements such as torsion. But perception and eye movements differ in how they utilize higher-level motion or expectation signals. The dissociations might indicate how each system optimally meets different functional demands: Perception relies on object segregation, whereas eye movements rely on signal integration.Medicine, Faculty ofGraduat
Eye movements as a continuous indicator of sensorimotor integration
No full textAdaptive behaviour in a highly dynamic and complex environment necessitates the ability to transform sensory input into motor output at different timescales. The goal of this dissertation was to probe the sensorimotor processes that underlie precise movement control in rich sensory environments. In four experimental studies, I studied different types of tracking eye movements in response to stimuli that mirror some of the complexities found in the natural environment (complex pattern motion, target acceleration, and audiovisual signals). In the first study, I investigated the dynamic motion integration processes that give rise to the coherent perception of 2D pattern motion. Comparing eye movements to observers’ perceptual experience revealed shared motion integration mechanisms that drive continuous tracking and motion perception (Chapter 2). Accurate sensing of complex motion signals is a fundamental ability that allows humans to interact with objects moving along complex trajectories. In Chapter 3, I investigated how observers track and manually intercept accelerating targets. Results showed that observers continuously monitor the changing target speed but fail to account for acceleration to predict and intercept targets. Natural interaction with moving visual objects typically involves multiple senses. In two studies, I demonstrated profound and rapid effects of audiovisual integration on goal-directed actions. I found that auditory and visual signals were weighted according to their uncertainty to guide interceptive movements (Chapter 4). Finally, presenting audiovisual distractors during continuous visual tracking revealed multisensory response enhancement of reflexive movement inhibition at short latencies of ~100 milliseconds (Chapter 5). These findings were obtained using eye movements as a continuous indicator of human sensorimotor integration, highlighting the use of eye movements as a model system to study adaptive sensorimotor behaviour in dynamic environments. I propose a model that describes how eye movements at different timescales are affected by the dynamic processing of complex visual and audiovisual signals. The present findings can be used to inform training protocols for interceptive sports athletes and to assess sensorimotor deficits in clinical populations.Medicine, Faculty ofGraduat
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Emotionen und Kontrollüberzeugungen beim komplexen Problemlösen : eine experimentelle Untersuchung anhand des computersimulierten Problemlöseszenarios FSYS 2.0
No full textDiese Studie untersucht den Einfluss positiver und negativer Emotionen auf komplexes Problemlösen unter Berücksichtigung der Kompetenz- und Kontrollüberzeugungen als Traits. 74 studentische männliche und weibliche Probanden bearbeiteten das computersimulierte Szenario FSYS 2.0 (Wagener & Conrad, 1997), anhand dessen sich Aussagen sowohl über die Problemlösegüte als auch das Problemlöseverhalten (z.B. Informationsmanagement) treffen lassen. Emotionen wurden vor Beginn des Szenarios und nach der Hälfte der Bearbeitung experimentell durch Leistungsfeedback induziert und begleitend durch Fragebögen erhoben. Kompetenz- und Kontrollüberzeugungen wurden mittels einer für den Kontext des Problemlösens modifizierten Version des Fragebogens zu Kompetenz- und Kontrollüberzeugungen (FKK; Krampen, 1991) erfasst. Die Ergebnisse zeigen, dass Emotionen keinen Effekt auf die Problemlösegüte hatten. Auf der Ebene des Problemlöseverhaltens führten negative Emotionen jedoch zu einer stärker informationsgeleiteten Vorgehensweise. Internal kontrollüberzeugte Probanden wiesen ein besseres Informationsmanagement sowie eine höhere Problemlösegüte auf als external Kontrollüberzeugte, wobei Kontrollüberzeugungen in Bezug auf die Problemlösegüte die Rolle einer Moderatorvariable einnehmen. Als wesentliche Prädiktoren des Problemlöseerfolgs wurden jedoch Intelligenz und Geschlecht der Probanden identifiziert
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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