Figure 8.

Age-related differences in spatial learning as assessed by a probe trial conducted during the first 30 s of the last trial of session 8. During this 30-s period, the platform was not available to the mouse. The number of mice of each age tested is shown in the bars in panel (d). In panels (a-c), the dotted line indicates the amount of time a mouse would spend in given areas based solely on chance. (a) Percent time spent swimming within a 40-cm annulus of the center of the platform. Old (24 month) mice spend significantly less time in the 40-cm annulus than do either 6-month-old or 16-month-old mice. (b) Percent time spent swimming within a 20-cm annulus of the center of the platform. Old (24 month) mice spend significantly less time in the 20-cm annulus than do either 6- or 16-month-old mice. (c) Percent time spent swimming in the quadrant of the Morris maze where the platform had been located. Old (24 month) mice spend significantly less time in the target quadrant than do either 6-month-old or 16-month-old mice. (d) Number of times a mouse entered the site where the platform had been located. Old (24 month) mice enter the target site significantly fewer times than 6-month-old mice. * Indicates that mice of the indicated age group differed significantly from 24-month-old mice (P<.05)