Specific Aspects in the Adaptation of Human Eye-Hand-Coordination

Sensorimotor control, especially eye-hand-coordination, enables us to interact with our environment. In my dissertation I describe and discuss three specific aspects of the adaptation of eye-hand-coordination: 1) the relative weight of visual and proprioceptive adaptation, 2) spatial and proprioceptive generalization of adaptation, and 3) acquisition of alternative mappings with repeated adaptations. The first aspect of sensorimotor adaptation is how an ambiguous mismatch between visual and proprioceptive coordinate systems is resolved. In my experiment I showed that an auditory pacing signal is an important factor facilitating visual adaptation. As a second aspect I examined the generalization of prism adaptation over space. Based on my results I can explain all previous results as an underestimation of change in the guiding system. The third aspect is the acquisition of alternate mappings (dual-adaptation) together with learning to learn. Confirming the involvement of learning to learn, I also found that the efficiency of dual-adaptation only depends on the total number of trials irrespective of their segmentation in blocks of differing lengths

Challenges in motor skill change: unraveling behavioral, cognitive and electrophysiological correlates of proactive interference

Changing automatized motor skills is a challenging endeavor. While often intended to raise or re-establish performance levels, this process is frequently associated with initial performance decrements. In this context, proactive interference has been theorized to play a particular role, as an already well-established and automatized procedural skill often hampers the acquisition or recall of the new target behavior. As a consequence, individuals must usually first overcome this interference which often renders skill change processes time-consuming and effortful. Despite its high practical relevance, there is only little research that has systematically investigated this topic so far. The aim of the present thesis was therefore to scrutinize the underlying mechanisms of proactive interference and its associated performance decrements in motor skill change. A multidisciplinary approach was pursued by empirically examining several individual and task-related factors which have been hypothesized to affect the amount of interference. To this end, a novel experimental paradigm was established which addressed the highly automatized motor skill of typing on a computer keyboard and that allowed to induce interference intentionally via different types of rule changes. In four experimental studies, including behavioral assessments, cognitive tests, eye-tracking and electroencephalography, several factors were identified to be associated with successful interference control in motor tasks: age, proficiency and prepotent response inhibition. Furthermore, there was a tendency towards a benefit of a motor restriction that limits individual motor degrees of freedom which might function as a potential inhibition support. These results provide first insights into the cognitive and electrophysiological mechanisms underlying motor skill modifications which in the long run might help to optimize motor skill change processes

Interference in learning internal models of inverse dynamics in humans

Experiments were performed to reveal some of the computational properties of the human motor memory system. We show that as humans practice reaching movements while interacting with a novel mechanical environment, they learn an internal model of the inverse dynamics of that environment. Subjects show recall of this model at testing sessions 24 hours after the initial practice. The representation of the internal model in memory is such that there is interference when there is an attempt to learn a new inverse dynamics map immediately after an anticorrelated mapping was learned. We suggest that this interference is an indication that the same computational elements used to encode the rst inverse dynamics map are being used to learn the second mapping. We predict that this leads to a forgetting of the initially learned skill.