In summary, the results of the present study are important
for six reasons. First, spatial reference memory deficits were
observed in rats as early as 11 months of age, suggesting a
nonlinear pattern of age-related spatial reference memory deficits
in Fischer-344 rats. Second, both spatial reference and
working memory deficits were observed in 24-month-old Fischer-
344 rats. Third, the repeated acquisition procedure was sufficiently
sensitive to detect age-related mnemonic impairments.
Fourth, the variable-interval probe trials were more sensitive to
age-related mnemonic changes than were the platform trials.
Fifth, the variability in performance of the 24-month-old group
was not significantly higher than that of the 4-month-old group.
Sixth, principal components analysis was a useful means of distinguishing
between measures of different mnemonic processes
in rats