Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 145-158).

Thesis (M.Sc. (Anatomy)) -- Mahidol University, 1976.

Some authors have argued that the primary function of the posterior parietal cortex is to control visual attention and awareness, whereas others have argued that the posterior parietal cortex is specialized for controlling actions. The purpose of the present thesis was to examine the influence of prism adaptation – a visuomotor adaptation technique – on visual attention deficits in patients with lesions of parietal cortex. Lesions to dorsal regions of the posterior parietal cortex lead to optic ataxia – a disorder in which visually guided reaching is disrupted. In contrast lesions to ventral (i.e. inferior) regions of the posterior parietal cortex of the right hemisphere lead to spatial neglect – a disorder in which patients are unaware of people or objects in contralesional (left) space. Chapter 1 presents an overview of the organization of the posterior parietal cortex, as well as an introduction to the disorders of spatial neglect and optic ataxia and the use of prism adaptation as a treatment for spatial neglect. Chapter 2 examined the influence of prism adaptation on attentional deficits in patients with right brain damage. Results demonstrated that prism adaptation reduced both the disengage deficit and the rightward attentional bias, two of the classic attentional deficits in neglect. Chapter 3 investigated the role of the dorsal posterior parietal cortex in controlling both reflexive and voluntary attention in two patients with optic ataxia. Lesions to the dorsal posterior parietal cortex led to both a disengage deficit and a rightward attentional bias, similar to patients with neglect, even though neither of the patients had any clinical symptoms of neglect. Contrary to previous work these results indicated that dorsal portions of the posterior parietal cortex – a region not commonly damaged in neglect – are important for controlling the orienting and reorienting of both reflexive and voluntary attention. Furthermore, these results indicated that optic ataxia is not purely a visuomotor disorder that is independent of any perceptual or attentional deficits as was previously assumed. Based on the results of Chapters 2 and 3 it was hypothesized that the beneficial effects of prism adaptation on attention may operate via the superior parietal lobe, a region which is typically undamaged in neglect, and is known to be important for controlling attention and action. Chapter 4 provided support for this hypothesis by demonstrating that a patient with lesions to the superior parietal lobe, who had the same attentional deficits as the right brain damaged patients tested in Chapter 2, failed to demonstrate any beneficial effects of prism adaptation on his attentional performance. Specifically, prism adaptation had no influence on his disengage deficit or his rightward attentional bias. Therefore, these data provide direct evidence that the beneficial effects of prisms on attention rely, at least in part, on the superior parietal lobe. Finally, Chapter 5 concludes with a summary of the research findings from the present thesis, and puts forward a new theory to conceptualize the mechanisms underlying the beneficial effects of prisms in patients with neglect.

Some authors have argued that the primary function of the posterior parietal cortex is to control visual attention and awareness, whereas others have argued that the posterior parietal cortex is specialized for controlling actions. The purpose of the present thesis was to examine the influence of prism adaptation – a visuomotor adaptation technique – on visual attention deficits in patients with lesions of parietal cortex. Lesions to dorsal regions of the posterior parietal cortex lead to optic ataxia – a disorder in which visually guided reaching is disrupted. In contrast lesions to ventral (i.e. inferior) regions of the posterior parietal cortex of the right hemisphere lead to spatial neglect – a disorder in which patients are unaware of people or objects in contralesional (left) space. Chapter 1 presents an overview of the organization of the posterior parietal cortex, as well as an introduction to the disorders of spatial neglect and optic ataxia and the use of prism adaptation as a treatment for spatial neglect. Chapter 2 examined the influence of prism adaptation on attentional deficits in patients with right brain damage. Results demonstrated that prism adaptation reduced both the disengage deficit and the rightward attentional bias, two of the classic attentional deficits in neglect. Chapter 3 investigated the role of the dorsal posterior parietal cortex in controlling both reflexive and voluntary attention in two patients with optic ataxia. Lesions to the dorsal posterior parietal cortex led to both a disengage deficit and a rightward attentional bias, similar to patients with neglect, even though neither of the patients had any clinical symptoms of neglect. Contrary to previous work these results indicated that dorsal portions of the posterior parietal cortex – a region not commonly damaged in neglect – are important for controlling the orienting and reorienting of both reflexive and voluntary attention. Furthermore, these results indicated that optic ataxia is not purely a visuomotor disorder that is independent of any perceptual or attentional deficits as was previously assumed. Based on the results of Chapters 2 and 3 it was hypothesized that the beneficial effects of prism adaptation on attention may operate via the superior parietal lobe, a region which is typically undamaged in neglect, and is known to be important for controlling attention and action. Chapter 4 provided support for this hypothesis by demonstrating that a patient with lesions to the superior parietal lobe, who had the same attentional deficits as the right brain damaged patients tested in Chapter 2, failed to demonstrate any beneficial effects of prism adaptation on his attentional performance. Specifically, prism adaptation had no influence on his disengage deficit or his rightward attentional bias. Therefore, these data provide direct evidence that the beneficial effects of prisms on attention rely, at least in part, on the superior parietal lobe. Finally, Chapter 5 concludes with a summary of the research findings from the present thesis, and puts forward a new theory to conceptualize the mechanisms underlying the beneficial effects of prisms in patients with neglect.

Many researchers have explored the way younger people perceive weight ratios using a variety of methodologies; however, very few researchers have used a more direct ratio estimation procedure, in which participants estimate an actual ratio between two or more weights. Of the few researchers who have used a direct method, the participants who were recruited were invariably younger adults. To date, there has been no research performed to examine how older adults perceive weight-ratios, using direct estimation or any other technique. Past research has provided evidence that older adults have more difficulty than younger adults in perceiving small differences in weight (i.e., the difference threshold for older adults is higher than that of younger adults). Given this result, one might expect that older adults would demonstrate similar impairments in weight ratio estimation compared to younger adults. The current experiment compared the abilities of 17 younger and 17 older adults to estimate weight ratios, using a direct ratio estimation procedure. On any given trial, participants were presented with two weights, and were asked to provide a direct estimate of the ratio, with the heavier in relation to the lighter. The results showed that the participants’ perceived weight ratios increased as a linear function of the actual weight ratios and that compared to younger adults, the older adults overestimated the weight ratios. The age-related overestimation was especially pronounced at higher weight ratios.

Thesis (M.S.)--Medical College of Ohio, 2004. / "In partial fulfillment of the requirements for the degree of Master of Science in Biomedical Sciences." Major advisor: Michael J. Dennis. Includes abstract. Document formatted into pages: iii, 62 p. Title from title page of PDF document. Includes bibliographical references (p. 57-61).

No / The right temporoparietal cortex plays a critical role in body representation. Here, we applied repetitive transcranial magnetic stimulation (rTMS) over right extrastriate body area (EBA) and temporoparietal junction (TPJ) to investigate their causative roles in perceptual representations of one's own and others' body. Healthy women adjusted size-distorted pictures of their own body or of the body of another person according to how they perceived the body (subjective task) or how others perceived it (intersubjective task). In keeping with previous reports, at baseline, we found an overall underestimation of body size. Crucially, EBA-rTMS increased the underestimation bias when participants adjusted the images according to how others perceived their own or the other woman's body, suggesting a specific role of EBA in allocentric body representations. Conversely, TPJ-rTMS increased the underestimation bias when participants adjusted the body of another person, either a familiar other or a close friend, in both subjective and intersubjective tasks, suggesting an involvement of TPJ in representing others' bodies. These effects were body-specific, since no TMS-induced modulation was observed when participants judged a familiar object. The results suggest that right EBA and TPJ play active and complementary roles in the complex interaction between the perceptions of one's own and other people's body.

Durch dynamische Aktivität im Gehirn kann ein Organismus auf seine Umwelt reagieren. Der Parietallappen spielt zwar in vielen Anforderungsbereichen eine Rolle, soll sich jedoch auf bestimmte Merkmale beschränken. Dieser Widerspruch könnte in Annahmen über Aufgabencharakteristika und deren Verbindung zu parietaler Aktivität begründet sein. Viele kognitive Modellen klammern die Konnektivität des Gehirns aus, zulasten ihrer biologischen Plausibilität. Die vorliegende kumulative Dissertation umfasst drei Manuskripte, die einige dieser Probleme ansprechen. Symbolische (arabische Zahlen) und nichtsymbolische (Punktewolken) Multiplikation und Division wurden zur Validierung des experimentellen Paradigmas sowie zur Untersuchung von Antwortverzerrungen (Operational Momentum) benutzt. Aufgrund der besseren Leistung in symbolischen Aufgaben, wurden aufgabenbezogene Konnektivitätsveränderungen in zerebralen und parietalen Seed-Regionen mit psychophysiologischer Interaktionsanalyse (gPPI) bei symbolischer Multiplikation geprüft. Zudem wurden bildgebende Daten einer nichtsymbolischen Schätzaufgabe sowie in unabhängigen funktionellen Lokalisieraufgaben erhoben. Parietale und sensorische Regionen wurden mittels multivariater Verfahren (multivoxel pattern analysis) analysiert. Die Ergebnisse dieser drei Studien legen nahe, dass parietale Aktivität eine wichtige bereichsübergreifende Bedeutung besitzt, die eventuell mit Aufgabenschwierigkeit und kognitiver Anforderung zusammenhängt. Der Beitrag sensorischer Regionen zu bereichsspezifischen Leistungen scheint bedeutender als bislang angenommen. Der Parietallappen interagiert mit dem Zerebellum und beide reagieren auf Schwierigkeit. Die abnehmende Konnektivität bei zunehmend komplexen Multiplikationen legt nahe, dass eine komplexitätsabhängige Modulation der Konnektivität wichtig für eine bedarfsabhängig adäquate Reaktion ist. Zusammen zeigen diese Ergebnisse wie verschiedene Gehirnregionen auf Umweltanforderungen reagieren. / The brain’s dynamic activity allows an organism to respond to its environment. The parietal lobe plays a role in responding to demands in many domains. However, it is also claimed to be specific to many task features. One reason for this contradiction may be assumptions about task features and their link to parietal activity. The connectivity within the brain has also been overlooked in many cognitive models, making them less biologically plausible. This cumulative dissertation presents three manuscripts that address some of these issues. Symbolic (Arabic digits) and non-symbolic (dot-arrays) multiplication and division were used to behaviorally validate an experimental paradigm as well as test response bias (operational momentum). Subjects accurately responded to symbolic problems, therefore symbolic multiplication problems were used to examine task-related connectivity changes from cerebellar and parietal seed regions using psycho-physiological interactions analysis (gPPI). Finally, brain imaging data from a non-symbolic estimation task and an independent functional localizer was collected. Parietal and sensory regions were analyzed using multi-voxel pattern analysis (MVPA). The results of the three studies suggest that parietal activity may reflect a more domain-general role, possibly related to task complexity and cognitive demand. Additional sensory regions also seem to play a larger role in domain specific task performance than previously assumed. Furthermore, the parietal lobe interacts with the cerebellum and both regions are involved in responding to task complexity. Cerebellar-parietal connectivity decreased during more complex multiplication, suggesting that increased connectivity during simple tasks and/or decreased connectivity during complex tasks, may be important for response to task demands. Together, these findings demonstrate the roles of multiple brain regions in responding to environmental demands.

Cette thèse a pour thème l'étude les mécanismes neurocognitifs impliqués dans la détermination de la latéralité intrinsèque d'objets. Dans une première étude, nous avons montré qu'une projection de son propre schéma corporel sur un objet est nécessaire pour en différencier la gauche de la droite. Cette inscription corporelle fut observée aussi bien pour des stimuli humains que non humains, suggérant que la présence d'axes intrinsèques à l'objet est suffisante pour y permettre la projection du corps. Une seconde étude nous a permis de mieux comprendre les mécanismes neuronaux de l'inscription corporelle, en utilisant une tâche de comparaison de formes identiques ou miroir différemment orientées. Les stimuli étaient soit des corps humains, soit des assemblages de cubes. La magnetoencephalographie (MEG) révéla une implication du lobe pariétal supérieur gauche dans l'incarnation et la transformation spatiale des deux stimuli. Par ailleurs, une contribution de l'aire motrice supplémentaire fut observée dans le cas des cubes. Ainsi, nous proposons de considérer le lobe pariétal supérieur comme le substrat neural d'un émulateur utilisant le schéma corporel afin d'encoder la latéralité d'un objet et de prédire les conséquences visuelles d'une transformation spatiale. La contribution additionnelle de l'aire motrice supplémentaire a probablement facilité la transformation de formes non familières, par l'envoi d'une commande motrice à l'émulateur visant à accroître la cohérence de l'objet tourné mentalement. Ces interprétations supportent l'idée d'une cognition incarnée dans les actions corporelles. / The aim of this thesis was to study the neurocognitive mechanisms implicated in the determination of objects intrinsic handedness. In a first study, we evidenced that distinguishing the left from the right of an object requires a mental projection of the body schema onto the stimulus. This embodiment process occured for human and non human stimuli as well, suggesting that the mere presence of intrinsic axes on stimulus enables the bodily projection. In a second study, we explored the neural mechanisms underlying embodiment in a handedness shape matching task, using human bodies and cubes assemblies as stimuli with different orientations. Magnetoencephalography (MEG) revealed that the left superior parietal lobe participated in the embodiment and spatial transformation of both stimuli. In addition, we observed a contribution of the supplementary motor area for cube assemblies specifically. Therefore, we consider the superior parietal lobe as the neural substrate of an emulator processing the body schema to encode handedness and to predict the visual consequences of a spatial transformation. Besides, the additional contribution of the supplementary motor area probably helped the spatial transformation of unfamiliar shapes by backpropagating a motor command to the emulator to increase cohesiveness of the mentally rotated object. These interpretations support the grounding of cognition in bodily actions.

Previous studies have demonstrated that rats exposed to methamphetamine (MA) during the neonatal period display deficits in spatial learning and memory. The underlying correlates are; therefore, this study was devised to determine whether neuronal changes occur in the dentate gyrus (DG), nucleus accumbens (NAcc) and cortex of adult rats exposed to 10 mg/kg MA administered four times daily from P11-20 using Golgi-Cox staining [Gibb, R. & Kolb, B. (1998) J. Neurosci. Meth., 79, 1-4]. The DG and NAcc demonstrated a decrease in the number of spines per neuron and the NAcc showed an associated decrease in dendritic length. Selective changes in cortex were observed because increased dendritic length in the parietal cortex occurred with no change in the number of spines, and no differences were noted for either dendritic length or spines in the medial frontal cortex. The data suggest a potential cause for the learning and memory deficits induced by neonatal MA exposure; however, the underlying mechanism that produces these neuronal changes is.