Pantomime von werkzeuggebrauch versus reale ausführung bei apraxie: Kinematische analysen

While apraxic patients frequently fail to pantomime the use of tools and objects, they typically perform much better during actual execution with real tools and objects. From this observation it was assumed that sensory cues from the physical objects facilitate the evocation of an action representation that is non-accessible during pantomime. Three-dimensional motion-analysis was used to analyse the relationship between pantomime and actual execution. Tool use actions (e.g.. "grasping a glass and drinking", "sawing") were investigated in apraxic patients and control subjects under different conditions of execution. Movement analysis revealed characteristic differences between conditions in control subjects. Apraxia in patients was apparent as errors of direction during pantomimed sawing movements and absent hand opening during pantomime of grasping. These movement characteristics were not obvious during actual execution. Interestingly, actual sawing was slowed in patients but this slowing did not correlate with the error of movement direction during pantomime. Different movement characteristics for the two conditions of executions suggest independent representations. Pantomimes may be represented as symbolic act, while actual execution may be determined by the physical demands of the task. Pantomime of tool use and actual tool use may be controlled by dynamic representations with varying similarities and differences during the time-course of an action.