Article Figures & Data
Figures
- Figure 1.
Chronic stress impairs conditioned approach directed at the CS+. A, Approach probability (mean ± SEM) directed at the CS across daily training sessions. Chronic stress (n = 30) reduced CS+ approach on day 7 compared with the Control condition (n = 29) (F(1,57) = 5.949, p = 0.0358, Holm-corrected). The CS– failed to promote approach in either condition. B, On day 7, conditioned goal approach (mean ± SEM) was quantified by calculating a difference score between goal approaches during the CS and goal approaches 10 s before the CS. Compared with the Control condition, chronic stress significantly increased goal approaches in response to the CS+ (F(1,57) = 9.493, p = 0.00317). C, PCA index (mean ± SEM) was calculated for all animals using CS+ and goal approach behavior in the manner of Meyer et al. (2012) (for analysis of individual components, see Extended Data Figure 1-1). A positive score indicates CS+-directed behavior, whereas a negative score indicates goal-directed behavior. This metric confirms the observation of a range of behavior in both groups, but a significant stress-induced change in approach behavior (F(1,54) = 10.81, p = 0.00178). Data from 3 control animals were not included in this analysis because of a computer error preventing the collection of CS approach latency data (Control: N = 26; Stress: N = 30).
- Figure 2.
Technical approach for fiber-photometric monitoring of PL-NAcC activity. A, Viral strategy for selective expression of GCaMP6(f) and example micrograph. NAcC: retrograde AAV2-CAG-Cre; PL: AAV1-hSyn-FLEX-GCaMP6f-WPRE.SV40. Fiber implanted in PL. B, Optical fiber placement in animals used for recording (Control: n = 13; Stress: n = 8). Circles represent histologically verified fiber tips that terminated in a region of the PL in which GCaMP6(f) expression was also verified. Open circles represent placements in Control animals. Closed circles represent placements in Stress animals.
- Figure 3.
Chronic stress does not alter non–task-related transient activity. Naturally occurring, non–task-related activity from a single Control (A) and Stress (B) animal. Each recording occurred 5 min before the onset of the autoshaping session on the first day (top) and last day (middle) of conditioning. Recordings were used to identify and count transients (activity peaks >2.91 median absolute deviations [MAD]). Bottom, A 20 s segment of an above trace with the MAD illustrated as a red horizontal line. C, Non–task-related activity was quantified for all animals in Stress (n = 8) and Control (n = 13) conditions. There was neither an effect of conditioning (F(1,19) = 0.9465, p = 0.3428) nor an effect of stress (F(1,19) = 0.0849, p = 0.7739) on transient frequency.
- Figure 4.
Chronic stress reduces CS+ evoked PL-NAcC Activity. A, Representative fiber photometric monitoring of trial × trial CS+ and CS– encoding in PL-NAcC neurons over 7 d of conditioning in a Control and Stress animal. Thirty second traces of ΔF/F (represented in pseudo-color) are aligned to 175 CS+ (solid line) and CS– (dashed line) trials for representative Control and Stress animals. Red triangle represents reward delivery. B, Mean (±SEM in shaded area) PL-NAcC activity during the beginning (Early Training) and last day (Late Training) of conditioning during CS+ (solid line) and CS– (dashed line) trials. Red triangle represents reward delivery. C, Activity (mean ± SEM) during the 10 s CS period and 10 s post-CS period was quantified as area under the curve (AUC) for each animal in each condition. In Control animals (n = 13), conditioning significantly increased pathway activity during CS+ (F(1,12) = 5.3627, p = 0.0391), but not CS–, trials. Stress (n = 8) prevented this effect. Control animals also showed a significant increase in activity during the post-CS+ period following conditioning, but not during the post-CS– period (F(1,12) = 6.9632, p = 0.0216). *indicates significance, p < 0.05. ns, not significant. Animals in the stress condition did not significantly alter pathway activity following training.
- Figure 5.
PL-NAcC activity is present during both CS+ and Goal approach behavior. A, Representative traces from individual trials in which Control animals displayed either a single CS+ approach (top, behavior for the duration of green overlay) or 3 separate Goal approaches (bottom, behavior for the duration of each red overlay). Red triangle represents reward delivery. B, PL-NAcC Activity (mean ± SEM) during different types of approach for Stress (n = 7) and Control (n = 11) animals that displayed both types of approach. Activity during CS versus Goal approaches did not differ (F(1,16) = 2.16, p = 0.161). Stress induced a general reduction in activity regardless of approach type (F(1,16) = 8.617, p = 0.0097). C, Individual differences in approach behavior and PL-NAcC activity in response to the CS+. Variability in the average signal during CS-prompted approaches is not explained by individual variation in the probability of exhibiting CS+ approach (Stress: r = 0.034, p = 0.943; Control: r = −0.094, p = 0.784).
Extended Data
Figure 1-1
Each of the measures that comprise the PCA index are illustrated. Results of analyses examining the effects of chronic stress on each measure revealed that stress consistently biased animals toward more “goal-tracking” like behaviors: A, Probability component: t(57) = 3.2167, p = 0.002139. B, Count component: t(57) = 3.4274, p = 0.001137. C, Latency component: t(54) = 2.9492, p = 0.0047. Data are presented as individual scores and mean ± SEM. Download Figure 1-1, TIF file.
