The human vestibulo-ocular reflex : effects of adaptation

This thesis systematically investigates the influence of adaptation on the human VOR-response. Various types of angular acceleration around the vertical axis are used to determine the time constants of the VOR-system. Care is taken as far as possible to avoid fatigue, habituation and the effects due to the order in which the experiments were done. Since each chapter was written as a paper dealing with a specific subject, the accompanying description of the problems under investigation and the references are contained within the chapters. In section I impulsive stimuli are used. The intra-subject variance and the inter-subject variance are investigated in chapter I. In chapters II and III the influence of the adaptation mechanism on the long time constant of the VOR is determined theoretically and experimentally. In section II sinusoidal stimulation is used. The theoretical and experimental frequency response of the VOR is described in chapters IV and v, and the effect of adaptation is determined at low frequencies. In section III constant angular acceleration is used as a stimulus. In chapter VI the theoretical response is calculated, while in chapter VII the results are given for a small group of subjects. These are not yet fully understood. The descriptions of the experiments are followed by a general discussion concerning the type of stimulus which appears to be the most suitable for the investigation of adaptation, and the extent to which the second order model with adaptation can account for the results obtained with the various stimuli. The appendix contains a comprehensive description of the derivation of the equations used.