Fig. 5.

Effects of age on performance in the Morris water maze. Rats received 8 days of training to swim to a hidden platform in the water maze. (A) Performance on acquisition trials, grouped into 5-trial blocks. Aged rats performed significantly worse than young (greater cumulative search error). (B) Performance on interpolated probe trials was used to calculate a “learning index” (see text for details), with higher values indicating less accurate search for the platform location. The learning index was used to divide rats into aged spatially unimpaired (Aged-SU, which performed comparably to young) and aged spatially impaired (Aged-SI, which performed significantly worse than young) subgroups for subsequent analyses of olfactory performance. Abbreviation: SEM, standard error of the mean.