Hermsdörfer, J. , Randerath, J. , Goldenberg, G. , Stadler, W. & Dieler, A.
Department of Sport and Health Science, Technische Universität München
Lesions of the left hemisphere following a stroke may lead to impaired use of common tools and objects in activities of daily living. Deficits of ADL performance is one manifestation of apraxia that is also characterized by errors in pantomime or imitation. To decipher the underlying deficit, we examined the relationship between performance with the tool in hand in a natural-like situation (condition Use), with the tool only (Demo), and without the tool (pure pantomime: Panto). Performance of 23 patients with left brain damage (LBD), 10 patients with right brain damage (RBD), and control subjects were tested on the non-paretic ipsilesional hand. The tasks “hammering” und “scooping” were conducted in the condition Panto, Demo, and Use. Video analyses were performed as well as kinematic analyses of arm and hand trajectories. Evaluation of movement errors revealed a clear prevalence of movement abnormalities in LBD patients and in the condition Panto as typically observed in apraxia. Compared to healthy controls the performance of LBD patients was however also impaired in the Use condition and factor analysis suggested communalities of the error patterns across the conditions. Similarly, the kinematic analyses revealed a gradient of errors from Panto to Use in LBD patients with significant correlations between characteristic movement variables such as movement direction and maximum velocity. The results show that in apraxic patients the lack of context is detrimental and presence of affordances is beneficial in using tools. A common factor seems to underlay aspects of the movement deficit independent of the condition of execution. The factor may be related to deficient tool manipulation knowledge, impaired mechanical reasoning, working memory deficits, errors of tool transformations (of the virtual or the real tool) and/or errors in considering the dynamic demands of the movement. Since variability is high and dissociations exist it is believed that multiple processes contribute to apraxia.