Article Figures & Data
Figures
- Figure 1.
Schematic of the risky decision making task. Each 40 s trial is initiated with the illumination of the house and food trough lights. A rat must nosepoke into the food trough to trigger the extension of one lever (forced-choice trials) or both levers (free-choice trials). A press on the small, safe lever yields 1 food pellet, delivered immediately. A press on the large, risky lever yields 2 food pellets, also delivered immediately, but accompanied by a varying probability of footshock delivery (0, 25, 50, 75, and 100%). After an intertrial interval ranging from 10 to 35 s (depending on how quickly the rat progresses through the trial components), a new trial begins.
- Figure 2.
Performance on the Risky Decision-making Task in young and aged rats. A, Aged rats made significantly fewer presses on the large, risky lever than young rats. B, Aged and young rats displayed comparable win–stay and lose–shift behavior in the RDT. C, Relative to latencies to press the small, safe lever, latencies to press the large, risky lever increased as the risk of punishment increased in young rats. D, Relative to latencies to press the small, safe lever, latencies to press the large, risky lever increased as the risk of punishment increased in aged rats. Data are represented as the mean (±SEM) number of large lever presses (A), the proportion of trials (B), or the latencies in seconds (C, D). *p ≤ 0.05.
- Figure 3.
Performance on a shock reactivity threshold assay in young and aged rats. Shock thresholds were not significantly different between young and aged rats. Data are represented as the mean (±SEM) shock reactivity threshold (in μA).
- Figure 4.
Performance on the probabilistic reversal learning task in young and aged rats. A, Aged rats completed fewer reversals over the eight sessions of testing compared with young rats. B, Data from the probabilistic reversal learning task were used to model the choice behavior of rats and to estimate learning rates. Learning rates significantly increased across the eight sessions of testing similarly in young and aged rats. C, The mean number of trials per block decreased across the eight sessions of testing similarly in young and aged rats. D, There was a significant decrease in stochasticity of choice behavior across the eight sessions of training that was evident in both young and aged rats. Data are represented as the mean (±SEM) number of reversals (A) or the learning rate parameters (B–D). *p ≤ 0.05.
- Figure 5.
Performance on the progressive ratio schedule of reinforcement assay in young and aged rats. Young rats lever pressed significantly more than aged rats. Data are represented as the mean (±SEM) number of lever presses. *p ≤ 0.05.
- Figure 6.
Functional connectivity between region-of-interest pairs in young and aged rats. Aged rats show greater resting-state functional connectivity than young rats among regions known to be critical to decision making under risk of punishment. A, Post hoc analyses indicate significant differences between young and aged functional connectivity for specific region-of-interest pairs. Asterisks denote p ≤ 0.05 after Bonferroni adjustment. B, C, Functional connectome maps of young (left) and aged (right) rats showing rostral-to-caudal (B) and ventral-to-dorsal (C) views of anatomically placed regions and their respective functional connections. Connectome maps were created with BrainNetViewer (Xia et al., 2013). Connecting “edges” are Fisher z-transformed Pearson’s r values.
Tables
- Table 1
Mean (±SEM) baseline locomotor activity, locomotor activity during shock delivery, and omissions in the risky decision making task
Locomotor activity
(locomotor units/ITI)Shock reactivity
(locomotor units/shock)Omissions Young 9.68 (2.04) 2.02 (0.27) 1.50 (0.67)* Aged 6.07 (1.25) 1.71 (0.23) 7.74 (2.56)* ITI, Intertrial interval.
*A main effect of age (p ≤ 0.05).
- Table 2
Correlation coefficients comparing risky decision making performance and functional connectivity between region of interest pairs in young and aged rats
Region of
interest pairGroup Spearman’s ρ correlation
coefficientp-Value† BLA.lOFC Young 0.184 0.547 Aged 0.1048 0.911 BLA.NAcSh Young 0.173 0.571 Aged 0.214 0.610 BLA.vOFC Young 0.234 0.442 Aged 0.024 0.955 lOFC.NAcSh Young 0.234 0.442 Aged 0.190 0.651 lOFC.PrL Young 0.382 0.197 Aged 0.095 0.823 lOFC.vOFC Young 0.283 0.348 Aged −0.095 0.823 BLA.PrL Young 0.492 0.087 Aged 0.357 0.385 PrL.NAcSh Young 0.377 0.204 Aged −0.095 0.823 PrL.vOFC Young 0.228 0.453 Aged 0.095 0.823 PrL.VTA Young −0.432 0.141 Aged −0.024 0.955 vOFC.NAcSh Young 0.498 0.083 Aged 0.381 0.352 BLA.VTA Young 0.204 0.505 Aged 0.476 0.233 lOFC.VTA Young 0.470 0.105 Aged 0.714 0.047* VTA.NAcSh Young −0.030 0.922 Aged −0.429 0.289 vOFC.VTA Young 0.083 0.789 Aged 0.714 0.047* *A significant correlation before corrections for multiple comparisons were made (p ≤ 0.05).
↵† p-Values reported without multiple comparisons correction.
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