The Visual Sensory Memory Task: : Integration of new knowledge and investigation for pattern separation using a new recognition memory task with abstract and similarty-adjustable stimuli

In classical memory tasks, it is often necessary to distinguish between old and new stimuli. Recent studies also use tasks in which stimuli appear that are similar to, but not identical with, familiar stimuli, so-called lures. These tasks were designed to study two postulated sub-functions of memory: Pattern separation and pattern completion. The stimuli are usually pictures of everyday objects, but for which different prior knowledge may influence memory performance and the degree of similarity between two pictures cannot be determined objectively. The Visual Sensory Memory Task (VSMT) developed by Kaernbach and colleagues is a visual pink noise-based task that can be used to construct lure stimuli with precisely quantifiable degrees of similarity. In this dissertation, existing test procedures and the newly developed test are first compared to investigate the validity of the VSMT. Then, the performance of the VSMT is transferred to different age groups to study the reliability of the VSMT, and finally, the neural processes in the hippocampus during memory retrieval are examined. The results of the first experiment demonstrate the validity of the VSMT as a neuropsychological measurement tool to study declarative memory. The second experiment showed that it is possible to perform the VSMT with different age groups and that the performance thereby shows the same profile in all age groups. In addition, it showed the expected better performance of young adults compared to four- to five-year-old children as well as adults over 65 years of age. The results of the third experiment confirm existing findings about the dentate gyrus as the central region of pattern separation and about the CA3 region as the core for the dynamic balance between pattern separation and pattern completion. Furthermore, they point to an involvement of the subiculum in pattern separation.