Averaged beta values as a function of group and condition in regions of interest to illustrate the results shown in <b>Figure 3</b>.

<p>Note that neural activity in the left auditory cortex was significantly enhanced in the L-dopa group compared to the placebo group without any significant differences between CS+ and CS− trials. Differences in CS+ and CS− trials were evident in dopaminergic brain regions (B and C). The plots further illustrates higher neural responses in the midbrain under L-dopa. Black bars show rewarded (CS+) trials, gray bars unrewarded (CS−) trials. Statistically significant differences are marked by asterisks (two factorial ANOVA corrected for multiple comparisons).</p

Results of the linear regression analysis using the slope of the individual learning curves: (A) L-dopa group, (B) placebo group and (C) differences between placebo and L-dopa.

<p>Results of the linear regression analysis using the slope of the individual learning curves: (A) L-dopa group, (B) placebo group and (C) differences between placebo and L-dopa.</p

Neural activity for main effect of group (A) and condition (B).

<p>Neural activity for (A) main effect of group, which yields stronger activation in the auditory cortex (AC), inferior frontal gyrus (Broca’s area) and anterior cingulate cortex (ACC)/left medial frontal gyrus for the L-dopa treated group compared to the placebo group. (B) Main effect of condition which shows stronger activation for rewarded (CS+) compared to non-rewarded tones (CS−), in several dopaminergic brain areas, such as nucleus accumbens (NAC) and midbrain regions (SN/VTA), as well as insula.</p

Effects of L-dopa during Auditory Instrumental Learning in Humans

<div><p>The dopaminergic neurotransmitter system is critically involved in promoting plasticity in auditory cortex. We combined functional magnetic resonance imaging (fMRI) and a pharmacological manipulation to investigate dopaminergic modulation of neural activity in auditory cortex during instrumental learning. Volunteers either received 100 mg L-dopa (Madopar) or placebo in an appetitive, differential instrumental conditioning paradigm, which involved learning that a specific category of frequency modulated tones predicts a monetary reward when fast responses were made in a subsequent reaction time task. The other category of frequency modulated tones was not related to a reward. Our behavioral data provides evidence that dopaminergic stimulation differentially impacts on the speed of instrumental responding in rewarded and unrewarded trials. L-dopa increased neural BOLD activity in left auditory cortex to tones in rewarded and unrewarded trials. This increase was related to plasma L-dopa levels and learning rate. Our data thus provides evidence for dopaminergic modulation of neural activity in auditory cortex, which occurs for both auditory stimuli related to a later reward and those not related to a reward.</p> </div

Results of the full factorial ANOVA with effects of drug treatment (A) and reward anticipation (B).

<p>Results of the full factorial ANOVA with effects of drug treatment (A) and reward anticipation (B).</p

Behavioral data.

<p>(A) Learning curves: Cumulative sum of correct answers to reward expectations as function of trial number for each individual subject. Bold lines (blue and red) indicate the mean of each group (L-dopa and placebo, respectively). Bold black lines indicate 100% and 50% (chance) correct answers. (B) Speed of instrumental responding: Reaction times in the number comparison task in rewarded (CS+, solid lines) and unrewarded (CS−, dashed lines) as function of trial number for each group.</p