Our brains remember the good stuff.

Anderson et al. show how our brains are attracted to items that have pleased us in the past, even if they are no longer relevant. People in a study were asked to look at a computer screen filled with colored objects and find the red and green ones, They received a small amount of money for each red or green object found. On the next day, the subjects were asked to find certain shapes on the screen, the color being irrelevant. Even so, when a red object appeared it captured attention, and PET brain imaging showed dopamine release in the ventral striatum, which plays a role in reward learning. Here is their technical abstract:

Highlights
•We examined the neural correlates of value-based attention using PET
•Previously reward-associated stimuli involuntary captured attention as distractors
•Such attentional capture was predicted by dopamine release in the dorsal striatum
•Our findings elucidate the neurochemical basis of value-based distraction

Summary
Reward learning gives rise to strong attentional biases. Stimuli previously associated with reward automatically capture visual attention regardless of intention. Dopamine signaling within the ventral striatum plays an important role in reward learning, representing the expected reward initiated by a cue. How dopamine and the striatum may be involved in maintaining behaviors that have been shaped by reward learning, even after reward expectancies have changed, is less well understood. Nonspecific measures of brain activity have implicated the striatum in value-based attention. However, the neurochemical mechanisms underlying the attentional priority of learned reward cues remain unexplored. Here, we investigated the contribution of dopamine to value-based attention using positron emission tomography (PET) with [11C]raclopride. We show that, in the explicit absence of reward, the magnitude of attentional capture by previously reward-associated but currently task-irrelevant distractors is correlated across individuals with changes in available D2/D3 dopamine receptors (presumably due to intrasynaptic dopamine) linked to distractor processing within the right caudate and posterior putamen. Our findings provide direct evidence linking dopamine signaling within the striatum to the involuntary orienting of attention, and specifically to the attention-grabbing quality of learned reward cues. These findings also shed light on the neurochemical basis of individual susceptibility to value-driven attentional capture, which is known to play a role in addiction. More broadly, the present study highlights the value and feasibility of using PET to relate changes in the release of a neurotransmitter to learning-dependent changes in healthy adults.