Seminar: Dr D. Sheynikhovich

2009-02-18 at 11:30

Where: conference room 501, Bat B, 5th floor, UPMC, 9 quai St Bernard, 75005 Paris


TITLE Modeling rat navigation: from cells to behavior

Modern psychological theories of spatial cognition postulate the existence of a geometric module for reorientation. This concept is derived from experimental data showing that in rectangular arenas with distinct landmarks in the corners, disoriented rats often make diagonal errors, suggesting their preference for the geometric (arena shape) over the non-geometric (landmarks) cues. Moreover, experimentally observed sensitivity of hippocampal cell firing to the changes in the environment layout was taken in support of the geometric module hypothesis. Using a computational model of rat navigation, we propose and test the alternative hypothesis that the influence of spatial geometry on both behavioral and neuronal levels can be explained by the properties of visual features that constitute local views of the environment. Our modeling results suggest that the pattern of diagonal errors observed in the reorientation task can be understood by the analysis of sensory information processing that underlies the navigation strategy employed to solve the task. In particular, two navigation strategies are considered: (i) a place-based locale strategy that relies on a model of grid and place cells, and (ii) a stimulus-response taxon strategy that involves direct association of local views with action choices. We show that the application of the two strategies in the reorientation task result in different patterns of diagonal errors, consistently with behavioral data. These results argue against the geometric module hypothesis by providing a simpler and biologically more plausible explanation for the related experimental data. Moreover, the same model can also describe behavioral results in watermaze tasks with fixed or variable starting conditions.