Fig. 1. Excess CORT exposure during adolescence impairs the ability of mice to update outcome expectancies in adulthood.

(A) Mice were trained to nose poke for food reinforcers in operant conditioning chambers. Next, the contingency between one response and its outcome was ‘degraded’ by providing food pellets independently of the mouse’s responses. The ability to update expectancies and select responses based on anticipated outcomes was then assessed in a brief choice test conducted in extinction. (B) Experimental timeline is above. First, mice exposed to excess CORT during adolescence were trained to nose poke as adults. All mice acquired the nose poke responses. “FR1” and “RI” denote the schedules of reinforcement used throughout. (C) A probe test following instrumental contingency degradation revealed that control mice preferentially engaged the response most likely to be reinforced (“non-degraded” vs. “degraded”), a goal-directed response strategy. Meanwhile, CORT-exposed mice generated habit-based response strategies, failing to differentiate between behaviors that were or were not likely to be reinforced. (D) Response rates were converted to preferences scores (“non-degraded”/“degraded”), again highlighting goal-directed responding in control mice (scores > 1) and non-preferential, habit-based responding following excess CORT (scores ~1). n = 8/group. (E) Separate mice were exposed to excess CORT in adulthood. In this case, CORT was insufficient to alter preference ratios. n = 6/group. Symbols in B represent means + SEMs, symbols in C–E represent individual mice, bars represent means ± SEMs. *p ≤ 0.05. B and C are reprinted from Barfield et al. (2017), and D and E were generated from a dataset originally reported in that manuscript. Experiments were conducted twice.