REDISTRIBUTION OF SPATIAL REPRESENTATION IN THE HIPPOCAMPUS OF AGED RATS PERFORMING A SPATIAL MEMORY TASK

Young and old rats performed on a maze according to a forced-choice an d then a spatial memory procedure either in the same or a different en vironment. Aged rats were slower to learn the spatial memory task when tested in the same, but not in a different, room. One interpretation of this pattern of results is that although old rats learn new rules a s quickly as young rats, they show less flexibility with old rules and familiar spatial information. Impaired choice accuracy during asympto te performance suggests poor processing of trial-unique information by old rats. Spatial correlates of hippocampal CA1 and hilar cells varie d with task demand: CA1 cells of aged rats showed more spatially selec tive place fields, whereas hilar cells showed more diffuse location co ding during spatial memory and not forced-choice, tests. Such represen tational reorganization may reflect a compensatory response to age-rel ated neurobiological changes in hippocampus.