Fig. 3.
A) Pre-trial (clear bars) baseline mean (± SEM) plasma cortisol levels compared to plasma cortisol response to presentation of conditioned stimulus (CS) alone on Day 8 (Gray bars). Presentation of CS alone on day 8 elicited a significant (*) increase in plasma cortisol compared to pre-trial levels only in non-escapers (hatching), and to post-trial escapers; B) Daily presentation of CS (open bars) or US (dotted bars) alone did not stimulate a conditioned response on Day 8; That is, 7 days of training with CS alone (CS+/US−) or US alone (CS−/US+) was insufficient to produce elevated plasma cortisol levels. A conditioned response to the CS on day 8 is only achieved with daily CS + US pairings (clear hatched bars compared to gray hatched bars).
