Figure 2.

Spatial discrimination performance in young and aged rats. (A) Rats first learned a match-to-position response strategy (Training Phase). A specific food well was baited and cued with an object (Sample). After a brief delay, rats were presented with two identical copies of the same cue object separated by a distance of 96 or 80 cm, covering the just-rewarded Target location and a Foil location (Choice). (B) Spatial discrimination performance was assessed by systematically varying the distance between Target and Foil locations (Discrimination Test Phase). (C,D) Young and aged rats acquired the match-to-position strategy within the same course of training. The two groups did not differ in their number of trials completed (C; P = 0.33) or in number of incorrect responses made (D; P = 0.29) prior to achieving criterion performance of ≥81.3% correct responses on two consecutive days. (E) Young and aged did not differ in their spatial discrimination performance across the final 5 d of training, based on the percent correct responses made (P = 0.66). (F) Spatial discrimination performance across easy (88 cm), difficult (48 cm), and very difficult (15 cm) spatial separations. Performance decreased significantly as a function of difficulty (main effect of distance: P < 0.001), such that performance on 88-cm trials was better than that on 48 cm or 15-cm trials across age groups (Ps < 0.01). Graphs show means ± SEMs. (**) P < 0.01 (***) P < 0.001.