Directionality And Laterality in the Compensatory Eye Movement System

Abstract

This thesis focuses on the role of the cerebellum in motor control and adaptation. Reflexive systems have gained attention as a model for cerebellar learning and multi-sensory integration on the molecular, cellular and behavioral level. But it is not yet completely understood how the respective mechanisms lead to the behavioral observations. Compensatory eye movements are a preferred model to study cerebellar control and adaptation in a motor task, because 1) the behavioral output is readily available, 2) several different adaptation paradigms exist, 3) multi-sensory, visual and vestibular information is integrated, and 4) the anatomical connectivity is well described. Therefore we developed a stimulation and recording setup that consists of a miniature high resolution rear-projection system for visual stimulation and a synchronized, servo-driven turntable, allowing vestibular stimulation in head-fixed awake-behaving mice. Motor performance was assessed by tracking of eye movements and electrophysiological recordings of neuronal responses. The CEM system is highly lateralized and spiking activity of cells correlates with eye movement direction. Here, we used a novel sigmoidal stimulus to investigate the influence of eye movement direction on cerebellar motor control and adaptation. One of the main findings was that learning success indeed depended on the movement direction and that neuronal correlates for specific adaptations reside in the cerebellum. In the following we will introduce the compensatory eye movement system with a focus on the cerebellum and multi-sensory areas. By first looking separately at the vestibular and visual sensory pathway (Chapter 1.1) the basic compensatory eye movement system is introduced. Including several multi-sensory loops (Chapter 1.2) we then extend the system and highlight the brain areas important for compensatory eye movements. Finally, we focus on motor adaptation under the control of the cerebellum in directional learning tasks (Chapter 1.3).