The head carries most of the sensory systems that enable us to function effectively in our three-dimensional habitat. Without adequate head movement control, efficient spatial orientation and motor responses to visual and auditory stimuli could not be carried out. This is the most comprehensive and up-to-date account of the control of vertebrate head movements and its biomechanical and neural basis. It covers the entire spectrum of research on head-neck movements, ranging from the global description and analysis of a particular behavior to its underlying mechanisms at the level of neurotransmitter release and membrane biophysics. Physiological and anatomical aspects are stressed. The role of head movements in upright stance and other functional contexts within the vertebrate hierarchy is juxtaposed with the mechanisms of orienting behavior in a number of invertebrates. This reveals a plethora of solutions among different animal species for the problem of orientation in three-dimensional space. Although head movement control in humans figures prominently in this volume, the anatomical-physiological comparisons show that the human system is not unique. The conference from which this volume originated surveyed current research and theory on motor control mechanisms in the head-neck sensory-motor system. It was held in Fontainbleau, France on July 17-24, 1989. The book provides a broad panorama of methodological and theoretical approaches to the field of head movement control.