Table 1.
Group characteristics
| PD with a depression (history) n = 21 | Nondepressed PD n = 22 | Healthy controls n = 23 | |
|---|---|---|---|
| Gender, men | 13 | 13 | 14 |
| Age (years) | 58.5 (5.8) | 61.0 (7.6) | 60.9 (5.9) |
| NART-IQ | 96.2 (11.6) | 97.0 (15.5) | 100.7 (13.7) |
| MMSE | 28.5 (1.4) | 28.6 (1.3) | 28.8 (1.2) |
| Hoehn & Yahr | 1.6 (0.4) | 1.8 (0.5) | – |
| UPDRSIII (OFF) | 22.7 (9.6) | 22.2 (6.5) | – |
| Disease duration (years) | 5.1 (3.5) | 4.5 (2.2) | – |
| LED (mg/day) | 551 (248) | 627 (275) | – |
| LED agonists (mg/day) | 71 (122) | 103 (129) | – |
| BDI (OFF) | 9.9 (6.1) | 4.0 (2.3) | 3.1 (2.1) |
| Current ICD | 4 | 1 | – |
| First session ON | 11 | 9 | – |
| Days between sessions | 23 (27) | 21 (20) | – |
| Endowment OFF session | 11.20 (1.08) | 10.52 (1.69) | 11.36 (1.76) |
| Endowment ON session | 11.28 (1.25) | 11.26 (1.42) | – |
[i] Note. Values represent numbers or mean (standard deviation).
Figure 1.
Task overview. Participants played a gambling task designed to measure loss aversion. During this task, participants were presented with 169 mixed gambles, each offering a 50/50 chance of either gaining or losing varying amounts of money. Gains ranged from +€6 to +€30 (increments of €2); losses ranged from −€3 to −€15 (increments of €1; see gainloss matrix). Each possible gainloss pair was presented once in randomized order. Participants were asked either to accept (play) or reject the gamble within a maximum time of 4 s.
Table 2.
Model parameters per group and drug session
| OFF session | ON session | |
|---|---|---|
| Gambling response bias (c) | ||
| PD with a depression (history) | −1.73 (14.9) | −1.30 (13.8) |
| Nondepressed PD | −2.71 (9.4) | −1.05 (8.9) |
| Healthy controls | −0.65 (11.1) | – |
| Loss aversion (λ) | ||
| PD with a depression (history) | 1.51 (3.0) | 1.19 (2.7) |
| Nondepressed PD | 1.01 (3.2) | 1.16 (2.6) |
| Healthy controls | 1.37 (2.8) | – |
| Inverse temperature (μ) | ||
| PD with a depression (history) | 0.93 (2.1) | 0.94 (1.9) |
| Nondepressed PD | 0.89 (1.5) | 1.09 (2.2) |
| Healthy controls | 1.06 (2.1) | – |
[i] Note. Values represent median (range).
Figure 2.
Drug effects on value-independent gambling bias. Median value-independent gambling bias parameter (c) per session (OFF session in dark gray; ON session in light gray) in nondepressed PD patients. For illustration purposes, we also added the bars for PD patients with a depression (history; OFF and ON sessions) and for healthy controls (OFF session). Error bars represent standard errors of the median. ** p < 0.01.
Figure 3.
Drug effects on loss aversion. Median loss aversion parameter (λ) per group (non depressed PD patients and PD patients with a depression [history]) and drug session (OFF session in dark gray; ON session in light gray). For illustration purposes, we also added the bar for healthy controls (OFF session). Error bars represent standard errors of the median. *p < 0.05.
Figure 4.
Loss sensitivity. The ratio of the number of rejected gambles divided by the number of accepted gambles in log-space (y axis) as a function of the relative loss averaged across different gain values (x axis) per group and per drug session. A steeper slope indicates greater loss sensitivity.
