Simulation of pharmacological results.

Update over the course of a single trial occurred according to the approximation in Eq. 7. To visually match the deviation of responses in medicated conditions from those of placebo, we have arbitrarily scaled the total update by α_η = 20 (note that α_η need not be <1) and set σ = 5 and T_max = 35 for the placebo condition. For the temporal estimates, we have plotted x_t=7 and x_t=17. We take the end point of temporal reproduction to occur at the peak of $\widehat{V}$_τ. For administration of DA agonists, we have chosen a gain modulation of 5 for positive RPEs and 0.2 for negative RPEs; for administration of DA antagonists, we have chosen a gain modulation of 0.2 for positive RPEs and 5 for negative RPEs. Finally, we have fixed the veridical time estimate to correspond to the baseline condition of unitary modulation of all RPEs (see Fig. 7).

Results from pharmacology compared with model behavior. A: in Lake and Meck (2013), subjects reproduced previously learned 7-s and 17-s intervals after administration of the dopamine (DA) agonist amphetamine (AMP), the DA antagonist haloperidol (HAL), or placebo. In the majority of subjects, amphetamine reduced response time, whereas haloperidol delayed it. Reprinted from Lake and Meck (2013) with permission from Elsevier. B: our model recapitulates these effects. See methods for simulation details.