Figure 8.

Average number of training trials required by each group to attain classic behavioral learning criteria and those criteria defined by the state-space model. Older T+ animals reached all learning criteria significantly faster than their yoked controls, while young T+ animals were not significantly different from their yoked counterparts on any criteria except 8/9 CRs. When behavioral criteria were organized according to early and later learning phases (5% and 10th CR vs. 8/9 CRs, 0.05 plateau and 80%), there was a highly significant interaction of age, treatment, and phase. Post hoc comparisons substantiated a significant benefit of theta triggering in the early phase for both young and older groups. In contrast, the later learning phase showed no theta-triggering benefit in young animals, but a continuing benefit in the older group. Asterisks indicate p < 0.05.