The neuroanatomical correlates of route learning impairment

Recent functional imaging studies of topographical learning point to the pa rticipation of a large network of cortical and subcortical regions. Neverth eless, areas which are crucial remain poorly specified due to the absence o f group studies of subjects with focal lesions distributed throughout the b rain. We assessed the ability of 127 subjects with stable, focal lesions to learn a complex real-life route, a critical aspect of topographical functi oning. Results indicated that impairment in route learning was highly assoc iated with damage to medial occipital and posterior parahippocampal cortice s in either hemisphere, the right hippocampus, and the right inferotemporal region. Impairment was seen among 86% of the subjects with damage to any t hese regions, in contrast to impairment among 31% of subjects with lesions in other regions. The importance of medial occipitotemporal cortices bilate rally and right inferotemporal cortex likely reflects the critical role of the ability to quickly and accurately perceive and learn multiple topograph ical scenes. The importance of the right (and probably left) posterior para hippocampal gyrus and of the right hippocampus likely reflects their critic al, distinctive roles forming an integrated representation of the extended topographical environment (i.e., the appearance of places and spatial relat ionships between specific places), and consolidating that representation in to multifaceted contextual knowledge of the environment. (C) 2000 Elsevier Science Ltd. All rights reserved.