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The cerebellum has historically been implicated solely in motor coordination. However, we now know it is a major associative center for sensory input. For example, the vestibulocerebellum (VbC) receives a large projection from retinal recipient nuclei in the Accessory Optic System and pretectum; these nuclei analyze visual optic flow information during self-motion and ultimately function in gaze stabilization. In birds, these nuclei project to the cerebellum directly, as mossy fibres, and indirectly as climbing fibres via the inferior olive. Therefore, there are parallel pathways carrying visual information to the cerebellum; these pathways show a remarkable modular organization. In fact, the pattern of cerebellar afferent and efferent connections, the physiological response properties of Purkinje cells, and a variety of molecular markers, all provide abundant evidence that the vertebrate cerebellum is organized into parasagittal zones. This modular organization exists across several different vertebrate species, suggesting that this basic principle of organization has been evolutionarily conserved and is necessary for fundamental information processing in the cerebellum. Although recent advances have increased our understanding of cerebellar organization, the relationship between these parasagittal patterns and the functional behavior of the cerebellum remains unknown. This dissertation seeks to tie together various features of the zonal organization of the cerebellum, using molecular, electrophysiological and neuroanatomical techniques, and to relate this organization to visual motion processing in the VbC. To investigate the parasagittal biochemical organization we use the molecular marker, zebrin (aldolase C), which is expressed by a subset of Purkinje cells, creating a striped appearance in the cerebellar cortex. We provide the first evidence of the zebrin parasagittal expression pattern in an avian species and then further elucidated the relationship between zebrin stripes and the visual afferent climbing fibre input, mossy fibre input, and the physiological zones in the VbC. There is a substantial, and growing, body of evidence that now suggests a more fundamental cerebellar architecture is built around arrays of parasagittal modules. By understanding the basic principles underlying this organization, we gain insights that may lead to a better understanding of the principles of modular organization in the central nervous system in general. / Neuroscience

名古屋大学博士学位論文 学位の種類 : 博士(医学)(課程) 学位授与年月日:平成6年3月25日 寳珠山稔氏の博士論文として提出された

名古屋大学博士学位論文 学位の種類 : 博士(医学)(論文) 学位授与年月日:平成4年12月22日 市川真澄氏の博士論文として提出された

No description available.

Traditionally, results from caloric testing and optokinetic nystagmus (OKN) testing are analyzed separately because caloric testing is a measure of peripheral function and OKN testing is considered to be a measure of central function. However, there is a connection between the visual system and the vestibular system in the vestibular nucleus of the brainstem. The purpose of this paper was to determine whether a relationship exists between optokinetic nystagmus results and unilateral caloric weakness results. This was determined by conducting a retrospective study of forty patients who exhibited a unilateral caloric weakness greater than or equal to twenty percent and symptoms consistent with an uncompensated vestibulopathy. Patients were later divided into two groups based on involved side. A control group consisting of ten subjects with no reported hearing or vestibular problems was also recruited. When the data of all subjects with a unilateral caloric weakness was considered together, no correlation was found between caloric response (right and left ear) and optokinetic results (gain and slow phase velocity). However, a potential trend emerged at the slow stimulus velocity (15 degrees) when comparing the patients with a right caloric weakness to those with a left caloric weakness. Subjects with a right caloric weakness showed decreased OKN gain for the right eye with a right-moving stimulus compared to the subjects with a left caloric weakness. Alternatively, subjects with a left caloric weakness showed decreased OKN gain for the left eye with a left-moving stimulus compared to the subjects with a right caloric weakness. We conclude that interpretation of OKN along with caloric results may offer potential for identification and tracking of compensation after a unilateral loss of vestibular function, but further research is needed.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 74-84).

Optokinetic nystagmus (OKN) is a fundamental gaze-stabilising response in which eye movements attempt to compensate for the retinal slip caused by self-motion. The OKN response consists of a slow following movement made in the direction of stimulus motion interrupted by fast eye movements that are primarily made in the opposite direction. The timing and amplitude of these slow phases and quick phases are notably variable, but this variability is poorly understood. In this study I performed principal component analysis on OKN parameters in order to investigate how the eigenvectors and eigenvalues of the underlying components contribute to the correlation between OKN parameters over time. I found three categories of principal components that could explain the variance within each cycle of OKN, and only parameters from within a single cycle contributed highly to any given component. Differences found in the correlation matrices of OKN parameters appear to reflect changes in the eigenvalues of components, while eigenvectors remain predominantly similar across participants, and trials. I have developed a linear and stochastic model of OKN based on these results and demonstrated that OKN can be described as a 1st order Markov process, with three sources of noise affecting SP velocity, QP triggering, and QP amplitude. I have used this model to make some important predictions about the optokinetic reflex: the transient response of SP velocity, the existence of signal dependent noise in the system, the target position of QPs, and the threshold at which QPs are generated. Finally, I investigate whether the significant variability within OKN may represent adaptive control of explicit and implicit parameters. iii

In comparison to mammals, zebrafish are able to regenerate many organs and tissues, including the central nervous system (CNS). Within the CNS-derived neural retina, light lesions result in a loss of photoreceptors and the subsequent activation of Müller glia, the retinal stem cells. Müller glia-derived progenitors differentiate and eventually restore the anatomical tissue architecture within 4 weeks. However, little is known about how light lesions impair vision functionally, as well as how and to what extent visual function is restored during the course of regeneration, in particular in adult animals. Here, we applied quantitative behavioral assays to assess restoration of visual function during homeostasis and regeneration in adult zebrafish. We developed a novel vision-dependent social preference test, and show that vision is massively impaired early after lesion, but is restored to pre-lesion levels within 7 days after lesion. Furthermore, we employed a quantitative optokinetic response assay with different degrees of difficulty, similar to vision tests in humans. We found that vision for easy conditions with high contrast and low level of detail, as well as color vision, was restored around 7–10 days post lesion. Vision under more demanding conditions, with low contrast and high level of detail, was regained only later from 14 days post lesion onwards. Taken together, we conclude that vision based on contrast sensitivity, spatial resolution and the perception of colors is restored after light lesion in adult zebrafish in a gradual manner.

Perceptual multistability is a phenomenon that is mostly studied in all modalities separately. The phenomenon reveals fundamental principles of the perceptual system in the formation of an emerging cognitive representation in the consciousness. The momentary perceptual organizations evoked during the stimulation with ambiguous stimuli switches between several perceptual organizations or percepts: The auditory streaming stimulus in audition and the moving plaids stimulus in vision, elicit different at least two percepts that dominate awareness exclusively for a random phase or dominance duration before an inevitable switch to another percept occurs. The similarity in the perceptual experience has led to propose a global mechanism contributing to the perceptual multistability phenomena crossmodally. Contrary, the difference in the perceptual experience has led to propose a distributed mechanism that is modality-specific. The development of a hybrid model has synergized both approaches. We accumulate empirical evidence for the contribution of a global mechanism, albeit distributed mechanisms play an indispensable role in this cross-modal interplay. The overt report of the perceptual experience in our experiments is accompanied by the recording of objective, cognitive markers of the consciousness: Reflexive movements of the eyes, namely the dilation of the pupil and the optokinetic nystagmus, correlate with the unobservable perceptual switches and perceptual states respectively and have their neuronal rooting in the brainstem. We complement earlier findings on the sensitivity of the pupil to visual multistability: It was shown in two independent experiments that the pupil dilates at the time of reported perceptual switches in auditory multistability. A control condition on confounding effects from the reporting process confines the results. Endogenous, evoked internally by the unchanged stimulus ambiguity, and exogenous, evoked externally by the changes in the physical properties of the stimulus, perceptual switches could be discriminated based on the maximal amplitude of the dilation. The effect of exogenous perceptual has on the pupil were captured in a report and no-report task to detect confounding perceptual effects. In two additional studies, the moment-by-moment coupling and coupling properties of percepts between concurrent multistable processes in audition, evoked by auditory streaming, and in vision, evoked by moving plaids, were found crossmodally. In the last study, the externally induced percept in the visual multistable process was not relayed to the simultaneous auditory multistable process: Still, the observed general coupling is fragile but existent. The requirement for the investigation of a moment-by-moment coupling of the multistable perceptual processes was the application of a no-report paradigm in vision: The visual stimulus evokes an optokinetic nystagmus that has machine learnable different properties when following either of the two percepts. In combination with the manually reported auditory percept, attentional bottlenecks due to a parallel report were circumvented. The two main findings, the dilation of the pupil along reported auditory perceptual switches and the crossmodal coupling of percepts in bimodal audiovisual multistability, speak in favor of a partly global mechanism being involved in control of perceptual multistability; the global mechanism is incarcerated by the, partly independent, distributed competition of percepts on modality level. Potentially, supramodal attention-related modulations consolidate the outcome of locally distributed perceptual competition in all modalities.:COVER 1 BIBLIOGRAPHISCHE BESCHREIBUNG 2 ACKNOWLEDGEMENTS 3 CONTENTS 4 CHAPTER 1: Introduction 6 C1.1: Stability and uncertainty in perception 6 C1.2: Auditory, visual and audio-visual multistability 14 C1.3: Capturing the subjective perceptual experience 25 C1.4: Limitations of preceding studies, objectives, and outline of the Thesis 33 CHAPTER 2: Study 1 “Pupillometry in auditory multistability” 36 C2.1.1 Experiment 1: Introduction 36 C2.1.2 Experiment 1: Material and Methods 38 C2.1.3 Experiment 1: Data analysis 44 C2.1.4 Experiment 1: Results 48 C2.1.5 Experiment 1: Discussion 52 C2.2.1 Experiment 2: Introduction 54 C2.2.2 Experiment 2: Material and Methods 54 C2.2.3 Experiment 2: Data analysis 56 C2.2.4 Experiment 2: Results 57 C2.3 Experiment 1 & 2: Discussion 61 C2.4 Supplement Study 1 65 CHAPTER 3: Study 2 “Multimodal moment-by-moment coupling in perceptual bistability” 71 C3.1.1 Experiment 1: Introduction 71 C3.1.2 Experiment 1: Results 74 C3.1.3 Experiment 1: Discussion 80 C3.1.4 Experiment 1: Material and Methods 84 C3.1.5 Experiment 1: Data analysis 87 C3.2 Supplement Study 2 92 CHAPTER 4: Study 3 “Boundaries of bimodal coupling in perceptual bistability” 93 C4.1.1 Experiment 1: Introduction 93 C4.1.2 Experiment 1: Material and Methods 98 C4.1.3 Experiment 1: Data analysis 102 C4.1.4 Experiment 1: Results 108 C4.1.5 Experiment 1: Discussion 114 C4.2.1 Experiment 2: Introduction 116 C4.2.2 Experiment 2: Material and Methods 119 C4.2.3 Experiment 2: Data analysis 125 C4.2.4 Experiment 2: Results 133 C4.3 Experiment 1 & 2: Discussion 144 C4.4 Supplement Study 3 151 CHAPTER 5: General Discussion 154 C5.1 Significance for models of multistability and implications for the perceptual architecture 162 C5.2 Recommendations for future research 166 C5.3 Conclusion 168 REFERENCES 170 APPENDIX 186 A1: List of Figures 186 A2: List of Tables 188 A3: List of Abbreviations and Symbols 189