"Cognitive Neuroscience throughout the last decade was dominated by a two stream model of visual processing. A ventral pathway was presumed to be dedicated to perception-related processing. A dorsal pathway was presumed to be dedicated to action-related processing. The proposed project challenges this view combining neuroimaging and neuropsychological methods. Neuroimaging in healthy humans allows for a view on correlated activity of the intact perception-action system, patients with visuomotor deficits reveal causalities between perception- and action-related information processing and the demonstration of neural reorganisation. However, neuroimaging studies including patients with brain lesions have rarely been conducted. Patients with optic ataxia after brain damage demonstrate specific visuomotor disorders: (i) deficient grip scaling to object size and (ii) spatial mismatch between perceived positions and goal-directed hand movements. These deficits vary with temporal parameters and knowledge about the object to be grasped and/or manipulated. Furthermore, the patients seem to adopt cognitive strategies to improve their performance. Therefore, they allow for the investigation of interactions between visual perception, spatial memory, and cognitive processing for the purpose of goal-directed action control. The proposed project comprises behavioural experiments to reveal the impact of object/action knowledge on movement control and of movement timing in optic ataxia patients. Investigations of reaching and grasping using functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation in healthy subjects and patients complement the neuropsychological research approach. The analysis of specific activation patterns and behavioural changes upon TMS application in patients - under consideration of their individual brain damage - in comparison with large groups of healthy controls will allow for a causal description of human visual action control."