Dopamine and the cognitive downside of a promised bonus

Abstract

It is often assumed that the promise of a monetary bonus improves cognitive control. We show that in fact appetitive motivation can also impair cognitive control, depending on baseline levels of dopamine-synthesis capacity in the striatum. These data not only demonstrate that appetitive motivation can have paradoxical detrimental effects for cognitive control but also provide a mechanistic account of these effects.

Keywords: PET; attention; cognition; dopamine; motivation; striatum.

Figure 1

Methods. (a) Left. Six striatal regions of interest (ROIs) were drawn on an anatomical MR image: left and right dorsal caudate nucleus, ventral striatum, and dorsal putamen. The MR image was subsequently coregistered to the PET images. Right. Averaged K_i values extracted from the ROIs were associated with performance in the task described in b. (b) In this example trial of the rewarded Stroop paradigm, the participant could earn a high reward (i.e., 15 cents) for a correct and fast enough answer on the incongruent arrow-word Stroop target. Participants were instructed to respond to the word of the targets (the correct response was a left button press in this trial). In this example, the information cue did not provide any information about the congruency of the upcoming target (i.e., uninformed trial).

Figure 2

Dopamine-dependent detrimental effects of reward on cognitive control. Dopamine synthesis capacity in the left caudate nucleus (on x-axis) predicted a detrimental effect of anticipated reward (high > low) on Stroop performance (RT: incongruent > congruent). Both measures were normally distributed. The correlation is still significant (r=.57, t(11)=2.3, p=.04) without the participant with the least FMT binding and the least detrimental effect of reward (lower left data point). This participant's x- or y-values do not represent outliers according to the Grubbs’ test (Barnett & Lewis, 1994), i.e. they do not differ more than 2.51*SD from the mean. The reported results are from uninformative trials only (see Fig. 1b). RT = response time; inc = incongruent; con = congruent; FMT = 6-[(18)F]-fluoro-L-m-tyrosine PET ligand; K_i = binding potential; r = Pearson's correlation coefficient.