, 2010 and Dreher et al., 2009). Finally, a second puzzle with respect to the effects of the DAT1 genotype was that the relationship between performance during acquisition and perseveration during reversals actually reverses sign as a function of genotype. The computational model explains this as the tradeoff between Selleckchem NVP-BKM120 two opposing effects.
For low ρ, as observed in 10R homozygotes, the computational model approaches standard temporal difference learning. In such a model, as discussed above, performance on the acquisition and reversal phases are coupled by a common, local adjustment mechanism, with the degree of correct choices versus errors in both phases determined by choice randomness (the inverse temperature) and the sluggishness of adjustment (the learning rate). This produces a negative correlation between correct choices at acquisition and errors at reversal (equivalently, a positive correlation between errors in either phase). However, as described above, for high ρ, as in the 9R genotype, the experience weighting mechanism produces the opposite effect. That is, increased choice of the correct stimulus during acquisition
will lead to increased perseveration on reversal and therefore predict a positive relationship between the two. This study revealed a functional double dissociation between the effects of polymorphisms in regulatory regions of the SERT and DAT1 genes. We showed that FDA approved Drug Library chemical structure within the same individuals, SERT is involved in behavioral adaptation following losses, whereas DAT1 plays a role in experience-based perseveration. Our results provide strong and direct evidence for a suggested, but hitherto untested, functional dissociation, but fail to find a direct opponency between serotonin and dopamine systems. Dichloromethane dehalogenase This study was part of the Brain Imaging Genetics (BIG) project at the Donders Institute for Brain, Cognition and Behavior, Radboud University Nijmegen. In the current study, 810 healthy, predominantly right-handed, Caucasian, highly
educated subjects completed an online probabilistic reversal learning task among a set of other tests (60.4% female; age 26.3 ± 11.1 years (mean ± SD); see Table S1 for full demographic information). The study was approved by the local ethics committee (CMO 2001/095) and written informed consent was obtained from all subjects prior to participation. Visual stimuli were probabilistically associated with positive (green, happy emoticon) and negative (red, sad/angry emoticon) feedback (Figure 1). We will refer to these positive and negative feedback events as “reward” and “punishment,” consistent with prior literature and the psychological definition of their tendency to increase/reduce response tendencies. On each trial, two stimuli were presented in two of four locations (left, right, top, or bottom of screen) and the subject was asked to select the usually rewarded stimulus with a mouse click.