Grundlagen der Prismenadaptation beim Menschen

Abstract

The sensory-motor system is crucial for the interaction of an organism with the environment. To be able to accomplish this interaction, it is essential to combine information from different sensory systems, for example information of the visual system, which betray information about the position of both the desired object as well as the arm, with proprioceptive information of the motor system. This combination is the basis for a correct motor command (Baraduc&Wolpert, 2002). Generally, in goal-driven pointing/throwing movements, information from the visual and the proprioceptive system normally correspond. Therefore, a pointing respectively throwing movement towards an object occurs without any problems (Kitazawa, Kohno,&Uka, 1995). But looking through prism glasses changes the position of the eyes relative to the head. This results in an initial pointing/throwing movement error in direction of the prismatic shift, the object is missed sideways (Efstathiou, 1969; Guan&Wade, 2000; Harris, 1963; Harris, 1965; Redding, Rossetti,&Wallace, 2005; Redding&Wallace, 2006; Taub&Goldberg, 1973). This mismatch occurs because spatial coordinates of the visual and proprioceptive system no longer match (Bornschlegl, Fahle,&Redding, 2012; Redding&Wallace, 1990; Redding&Wallace, 1993). However, to restore the previous conditions, the organism is able to adapt to the new conditions, in this case to the prismatic shift. The spatial coordinates will be adjusted gradually, by pointing/throwing under visual feedback (Baraduc&Wolpert, 2002; Bornschlegl, Fahle,&Redding, 2012; Cohen, 1967; Efstathiou, 1969; Harris, 1963; Harris, 1965; Hay&Pick, 1966; Redding, Rossetti,&Wallace, 2005; Redding&Wallace, 2006; Taub&Goldberg, 1973). After removing the prisms, again a point movement occurs, now opposite to the prismatic displacement (Cohen, 1967; Guan&Wade, 2000; Redding, Rossetti,&Wallace, 2005; Taub&Goldberg, 1973). It can be reduced gradually under visual feedback, with the result that the spatial coordinates are adjusted again. The adaptation of the eye-hand coordination, more specifically the prism adaptation, at the first glance seems to be a relative simple process, which allows a fast error correction. But a more detailed look shows a complex system. For a better understanding of this complex system, since Helmholtz (1867) a large number of studies have been conducted on this topic. But despite this variety of studies and their methods, until today some basic questions were not answered satisfactorily. These include 1) the not quite understood immediate correction effect, 2) the question to what extend it is connected with the body rotation and/or subconscious head- and eye position and 3) the question whether or not prism adaptation has an influence on the auditory system. The present dissertation deals with the aforementioned unsolved questions in prism adaptation.