Funktionelle Gehirnasymmetrien bei der Verarbeitung globaler und lokaler Merkmale visueller Szenen

Abstract

Many aspects of the world we perceive are structured hierarchically. For instance, a house consists of walls, doors, windows, a roof and several other components. Presumably, those different levels of a hierarchic object are processed in parallel by our brain and therefore distributing these processes to different brain structures seems useful. Based on this assumption the question is addressed, as to whether the left and right cerebral hemispheres contribute differentially to the processing of hierarchically structured visual information and, more specifically, what the nature of these differences is. In the first part the 'state of the art' is structured and analyzed in detail. Then, in five own experiments the question is addressed, as to how stimulus properties as well as attentional processes influence the lateralization of the involved processes. For this purpose hierarchical letters - larger (global) letters that are created by arranging several identical smaller (local) letters - are presented for a short time in the left or right visual field. With this it controlled, which hemisphere receives the information first. The participants are asked to respond either to the global or the local level of the presented stimulus. The results of the experiments confirm what the literature review already suggested. Theoretical models that merely assume differences in the perceptual processing cannot fully account for the findings, that differences between the right and left hemisphere mainly occurred, when there was a response conflict, i.e. when local and global information required different responses. Taken together the results support the idea of dynamic interactions between the two hemispheres. It might be, that the processing is transferred to the specialized hemisphere (the right one for global, the left one for local) only when the demands or the complexity of a task are relatively high.