A subset of aged Long-Evans rats displays impaired spatial memory.

<p>(A) Learning index scores (a weighted measure of proximity to the platform location across interpolated probe trials) for individual young and aged rats in a standardized spatial version of the Morris water maze. Aged rats (24 mos) that scored within the range of young (Y; 6 mos) were classified as aged unimpaired (AU) and the remainder were classified as aged impaired (AI). (B) Redundant place/cue (RPC) task schematic (top), and escape performance during training, measured as pathlength, in Y, AU, and AI subjects. (C) AI animals displayed impaired spatial learning in the RPC task relative to Y and AU animals, measured as the difference in average pathlength between the last four hidden and visible trials. (D) All groups showed significant spatial bias, measured as proximity to the goal location, during a probe trial provided two hours after the onset of RPC training. Error bars = S.E.M; asterisks indicate p-values<0.05.