Risk-taking in patients with ICD.
ICD is characterized by a sudden increase in risky decisions caused by dopaminergic therapies. To test the hypothesis that patients with a history of ICD are in a predisposition that may be revealed by the ICD-inducing medications, we compared risk taking behavior in patients with a history of ICD, versus patients without a history of ICD, in an off-medication state. The decision to gamble occurred at the same rate in both groups (Supplemental Table 2) and was also not affected by medication state (off-medication, ICD = 46.98%, non-ICD = 46.04%, p-value = 0.9502; on-medication, ICD = 44.96%, non-ICD = 47.57%, p-value = 0.3048; ICD-on versus ICD-off, p-value = 0.7666; non-ICD-on versus non-ICD-off, p-value = 0.4023). Factors that drive the decision to gamble were similar in the two groups. A logistic regression fit to participants’ decision to gamble revealed that both groups’ decisions to gamble were positively influenced by the value of the “expected value of the gamble” and negatively influenced by the value of the “certain reward” in both on and off medication states, as expected (Table 1).
Table 1
Gamble choice model parameters. The “decision to gamble” on each trial was modeled as a dependent binary outcome with the independent variables being the “expected value of the gamble option”, “certain reward value”, and the participants actual or imputed “subjective feeling rating on the previous trial”, and a constant term “Baseline”. 𝜷x – coefficients for each independent variable were fit in a logistic regression and reported.
OFF Medication
|
Non-ICD Off Medication
|
|
|
ICD Off Medication
|
|
|
Model Parameter
|
Parameter Estimate
|
95% Confidence Interval
|
P-value
|
T-Statistic
|
Parameter Estimate
|
95% Confidence Interval
|
P-value
|
T-Statistic
|
Baseline (𝜷𝟎)
|
0.141
|
-1.124 to
1.405
|
0.811
|
0.245
|
0.228
|
-0.644 to
1.099
|
0.588
|
0.551
|
Gamble EV(𝜷1)
|
2.068
|
1.658 to
2.478
|
0.000
|
11.089
|
1.796
|
1.309 to
2.283
|
0.000
|
7.780
|
Certain Reward EV(𝜷2)
|
-1.828
|
-2.244 to
-1.411
|
0.000
|
-9.657
|
-1.715
|
-2.159 to
-1.272
|
0.000
|
-8.159
|
Subjective Feeling on (t-1) (𝜷3)
|
0.045
|
-0.628 to
0.718
|
0.885
|
0.148
|
-0.088
|
-0.799 to
0.624
|
0.798
|
-0.260
|
ON Medication
|
Non-ICD On Medication
|
|
|
ICD On Medication
|
|
|
Model Parameter
|
Parameter Estimate
|
95% Confidence Interval
|
P-value
|
T-Statistic
|
Parameter Estimate
|
95% Confidence Interval
|
P-value
|
T-Statistic
|
Baseline (𝜷𝟎)
|
0.269
|
-0.324 to
0.862
|
0.340
|
0.998
|
-0.253
|
-2.675 to
2.169
|
0.828
|
-0.220
|
Gamble EV(𝜷1)
|
1.826
|
1.448 to
2.204
|
0.000
|
10.620
|
2.012
|
1.564 to
2.459
|
0.000
|
9.492
|
Certain Reward EV(𝜷2)
|
-1.727
|
-2.142 to
-1.311
|
0.000
|
-9.141
|
-1.799
|
-2.228 to
-1.371
|
0.000
|
-8.858
|
Subjective Feeling on (t-1) (𝜷3)
|
-0.123
|
-0.286 to
0.04
|
0.125
|
-1.660
|
0.173
|
-1.008 to
1.353
|
0.762
|
0.308
|
Predictors of subjective feelings differentiate ICD-history in off-medication state.
We next tested the hypothesis that the influence of objective decision-making variables on participants’ subjective experience would be different in patients with a history of ICD versus those without (Table 2). Subjective feeling (i.e., ‘Happiness’) model parameters for patients in the off-medication state were significantly different across ICD and non-ICD groups (Table 2a). Post-hoc Tukey HSD comparisons of ICD versus non-ICD groups’ subjective feeling parameters are reported in Table 2a. The ICD group had a significantly greater influence of recent events (\(\gamma\), MD = 0.2947, p 0.0000, 95% C.I.=[0.197, 0.3924], Table 2a). The non-ICD group was significantly more positively influenced by the collection of ‘certain rewards’ than the ICD group for which the weight of certain rewards was nearly noncontributory (\({w}_{1}\), MD=-0.0497, p = 0.0008, 95% C.I.=[ -0.082, -0.0175], Table 2a). The ‘expected value of chosen gambles’ negatively impacted subjective feelings in the ICD group, whereas these expectations positively impacted subjective feelings in the non-ICD group (\({w}_{2}\), MD=-0.1166, p = 0.0000, 95% C.I.=[-0.1653,-0.0678], Table 2a). Finally, the reward prediction error associated with the gamble outcome had a significantly greater positive influence on subjective feelings in the non-ICD group compared to the ICD group (\({w}_{3}\), MD=-0.2247, p = 0.0001, 95% C.I.=[-0.3489,-0.1006], Table 2a).
Table 2
Happiness model parameter comparisons: ICD versus non-ICD. Participants ‘happiness’ with their decision outcomes were modeled as the dependent variables using Eq. 1. Parameter weight estimates and confidence intervals for each group (ICD and non-ICD) and medication state (on and off) were determined using hierarchichal baysiean modeling. Difference in means (MD) and confifdence intervals (95% CI) for comparisons across ICD-off versus non-ICD-off (2a) or ICD-on versus non-ICD-on (2b) with corresponding p-value are reported.
2a. OFF Medication
|
|
Baseline (w0)
|
Certain Reward (w1)
|
Gamble EV (w2)
|
RPE (w3)
|
Recent Experience Weight (g)
|
ICD Off Medication
|
Parameter Estimate
|
1.882
|
0.018
|
-0.059
|
0.085
|
0.874
|
95% Confidence Interval
|
1.344
|
0.015
|
-0.077
|
0.081
|
0.856
|
to
|
to
|
to
|
to
|
to
|
2.42
|
0.021
|
-0.04
|
0.089
|
0.892
|
Non-ICD Off Medication
|
Parameter Estimate
|
1.086
|
0.068
|
0.058
|
0.31
|
0.58
|
95% Confidence Interval
|
0.709
|
0.04
|
0.049
|
0.163
|
0.485
|
to
|
to
|
to
|
to
|
to
|
1.464
|
0.096
|
0.067
|
0.457
|
0.675
|
ICD Off :
non-ICD Off
|
Difference in Means (MD)
|
0.7959
|
-0.0497
|
-0.1166
|
-0.2247
|
0.2947
|
95% Confidence Interval
|
-0.0776
|
-0.082
|
-0.1653
|
-0.3489
|
0.197
|
to
|
to
|
to
|
to
|
to
|
1.6693
|
-0.0175
|
-0.0678
|
-0.1006
|
0.3924
|
P-value
|
0.0863
|
0.0008
|
0
|
0.0001
|
0
|
2b. ON Medication
|
|
Baseline (w0)
|
Certain Reward (w1)
|
Gamble EV (w2)
|
RPE (w3)
|
Recent Experience Weight (g)
|
ICD On Medication
|
Parameter Estimate
|
1.763
|
0.041
|
-0.013
|
0.101
|
0.733
|
95% Confidence Interval
|
1.263
|
0.024
|
-0.022
|
0.047
|
0.673
|
to
|
to
|
to
|
to
|
to
|
2.262
|
0.057
|
-0.005
|
0.155
|
0.793
|
Non-ICD On Medication
|
Parameter Estimate
|
1.928
|
0.018
|
-0.166
|
0.281
|
0.697
|
95% Confidence Interval
|
1.601
|
-0.009
|
-0.228
|
0.221
|
0.663
|
to
|
to
|
to
|
to
|
to
|
2.255
|
0.044
|
-0.104
|
0.341
|
0.731
|
ICD On :
non-ICD On
|
Difference in Means (MD)
|
-0.1657
|
0.0229
|
0.1522
|
-0.18
|
0.0359
|
95% Confidence Interval
|
-1.0392
|
-0.0093
|
0.1034
|
-0.3042
|
-0.0618
|
to
|
to
|
to
|
to
|
to
|
0.7078
|
0.0552
|
0.2009
|
-0.0559
|
0.1335
|
P-value
|
0.9582
|
0.2467
|
0
|
0.0018
|
0.7658
|
Dopaminergic medications differentially influence predictors of subjective experience in ICD and non-ICD groups.
The ‘the expected value of chosen gambles’, collection of ‘certain rewards’, and ‘reward prediction errors’ about chosen gambles are hypothesized to engage or be affected by the dopaminergic system; thus, we hypothesized that the impact of these variables on subjective experience would be modulated by dopaminergic medications used to treat PD symptoms (Table 2b). In patients without a history of ICD, the influence of the ‘certain reward’, ‘expected value of the gamble’, and ‘recent experience’ were significantly different in the on-medication state (Table 3a): the influence of the ‘certain reward’ and ‘expected value of the gamble’ decreased (Table 3a) and the influence of ‘recent experience’ increased (Table 3a). In patients with a history of ICD, the influence of the ‘expected value of the gamble’ remained negative but decreased in magnitude (Table 3b); and the influence of the ‘recent experience’ decreased (Table 3b). The influence of the ‘reward prediction error’ did not change in either patient group (Table 3a and Table 3b).
Table 3
Happiness model parameter comparisons: On versus Off medication. Participants ‘happiness’ with their decision outcomes were modeled as the dependent variables using Eq. 1. Parameter weight estimates and confidence intervals for each group (ICD and non-ICD) and medication state (on and off) were determined using hierarchichal baysiean modeling (Table 2). Difference in means (MD) and confifdence intervals (95% CI) for comparisons across non-ICD-on versus non-ICD-off (3a) or ICD-on versus ICD-off (3b) with corresponding p-value are reported.
3a. non-ICD On : non-ICD Off
|
Difference in Means (MD)
|
95% Confidence Interval
|
P-value
|
Baseline (w0)
|
0.8418
|
-0.115
|
to
|
1.7987
|
0.1035
|
Certain Reward (w1)
|
-0.0502
|
-0.086
|
to
|
-0.015
|
0.0022
|
Gamble EV (w2)
|
-0.2235
|
-0.277
|
to
|
-0.17
|
0
|
RPE (w3)
|
-0.0286
|
-0.165
|
to
|
0.1074
|
0.9441
|
Recent Experience Weight (g)
|
0.1174
|
0.0104
|
to
|
0.2244
|
0.0262
|
3b. ICD On : ICD Off
|
Difference in Means (MD)
|
95% Confidence Interval
|
P-value
|
Baseline (w0)
|
-0.1198
|
-0.901
|
to
|
0.6615
|
0.9772
|
Certain Reward (w1)
|
0.0225
|
-0.006
|
to
|
0.0513
|
0.1767
|
Gamble EV (w2)
|
0.0452
|
0.0016
|
to
|
0.0888
|
0.0391
|
RPE (w3)
|
0.0161
|
-0.095
|
to
|
0.1271
|
0.9807
|
Recent Experience Weight (g)
|
-0.1414
|
-0.229
|
to
|
-0.054
|
0.0004
|
The addition of dopaminergic medication significantly changed the influence of dopamine-related decision-making variables in both ICD and non-ICD groups. Notably, the impact of these changes was that the influence of these variables for both groups became more similar except for the influence of the ‘expected value of the gamble’ and the ‘reward prediction error’ of those outcomes (Table 2b). ICD and non-ICD showed a negative influence of the ‘expected value of the gamble’ with ICD being influenced significantly less (\({w}_{2}\), MD = 0.1522, p = 0.0000, 95% C.I.=[0.1034,0.2009], Table 2b). ICD also showed a significantly reduced influence of the ‘reward prediction error’ (\({w}_{3}\), MD=-0.18, p = 0.0018, 95% C.I.=[-0.3042, -0.0559], Table 2b). No difference between groups was observed for the influence of the ‘certain reward’, ‘recent experience’, or ‘baseline’ subjective feelings (Table 2b).