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Abstract:
Many studies examine the neural correlates of spatial me- mory for a known environment, yet only few accompa- ny the process of building a spatial representation of new surroundings. Using fMRI, we investigated the course of spatial learning over two one-hour sessions on two con- secutive days, while participants searched for objects in two virtual environments. The spatial layout of one en- vironment was held constant over all trials, allowing for memory formation, whereas the other changed its layout constantly outside the current field of view to prevent spa- tial learning of any kind. Comparing BOLD signal in both conditions, we find a well-established network of regions involved in spatial processing, including occipital, parietal and frontal regions, with the exception of the hippocam- pus. Spatial learning is most prominently accompanied by increasing activity in parietal areas, mainly the precuneus and the retrosplenial complex. This effect can be obser- ved over time spent navigating the environment, as well as over the number of previous encounters with a location. The hippocampus, on the other hand, exhibits increased activity in the memorizable environment only during the very first encounters with a location, which supports its role in novelty detection. Moreover, connectivity between the precuneus and hippocampus decreases in response to an increasing number of previous encounters with a loca- tion. Together our results point towards memory-related spatial processing further upstream than has previous- ly been assumed, with parietal associative regions supporting an independent spatial memory representation already early in the learning process.
