General principles of cerebellar organization: correlating anatomy, physiology and biochemistry in the pigeon vestibulocerebellum

• Main Author: Pakan, Janelle
• Other Authors: Dr. Douglas Wylie (Psychology)
• Format: Others
• Language: en
• Published: 2009
• Subjects: Cerebellum; Vestibulocerebellum; Optokinetic; Zebrin; Accessory Optic System
• Online Access: http://hdl.handle.net/10048/530

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