LANDMARK STABILITY IS A PREREQUISITE FOR SPATIAL BUT NOT DISCRIMINATION-LEARNING

NEURONS sensitive to both place and direction from distinct regions of the hippocampal formation1,2, allometric relationships between spatial learning and hippocampal structure3,4 and pronounced impairments in spatial learning after lesions in this area5-8, indicate that the hippocampal formation subserves allocentric spatial learning9,10. To learn more about the process of spatial representation, we have developed a task that provides independent control of both landmark and directional cues. On the basis of physiological11 and behavioural12 work, this task also makes it possible to investigate the relevance of associative learning principles, such as predictability13, to the spatial domain. We report here that although rats learn to discriminate between landmarks on the basis of their proximity to a reliably predicted food reward, they will only learn to use them to represent its location if they maintain stable locations within a geometric frame of reference.