Figure 1. Behavioral task and hypothesis.
(a) In ‘choice trials’ two visual cues were simultaneously presented on a computer screen. The participant was required to make a choice within 1.5 s. The chosen option and the outcome then appeared for 1 s, followed by a variable inter-trial interval. (b) Theoretical framework. Top: trials in which the risky cue is chosen and the obtained outcome is larger than expected (trials with a 10¢ outcome) should result in strengthening of corticostriatal connections (LTP), thereby increasing the expected value of the cue and the tendency to choose it in the future. Conversely, outcomes that are smaller than expected (0¢) should cause synaptic weakening (LTD) and a resulting decrease in choice probability. Middle: In DYT1 dystonia patients (red solid), increased LTP combined with decreased LTD are expected to result in an overall higher learned value for the risky cue, as compared to controls (blue dashed). In the model, this is reflected in higher probability of choosing the risky cue when presented together with sure 5¢ cue (Bottom). Simulations (1000 runs) used the actual order of trials and mean model parameters of each group as fit to participants’ behavior. Gray shadow in the middle plot denotes trials in the initial training phase.