Stimuli associated with high rewards evoke stronger neuronal activity than stimuli associated with lower rewards in many brain regions. It is not well understood how these reward effects influence activity in sensory cortices that represent low-level stimulus features. Here, we investigated the effects of reward information in the primary visual cortex (area V1) of monkeys. We found that the reward value of a stimulus relative to the value of other stimuli is a good predictor of V1 activity. Relative value biases the competition between stimuli, just as has been shown for selective attention. The neuronal latency of this reward value effect in V1 was similar to the latency of attentional influences. Moreover, V1 neurons with a strong value effect also exhibited a strong attention effect, which implies that relative value and top-down attention engage overlapping, if not identical, neuronal selection mechanisms. Our findings demonstrate that the effects of reward value reach down to the earliest sensory processing levels of the cerebral cortex and imply that theories about the effects of reward coding and top-down attention on visual representations should be unified.object-based attention | reward expectancy R eward and punishment shape behavior. The representations of actual and anticipated rewards in the brain are widespread and multifaceted (1-4). There are many brain areas that code the value, taste, and other perceptual qualities of incentive stimuli (5-14). Furthermore, rewards are motivating. Motivational effects influence neuronal activity in brain structures responsible for goal-directed behavior in cortex, in the basal ganglia, and also at the level of the superior colliculus where neurons increase their activity if larger rewards can be obtained (1,3,9,(15)(16)(17)(18)(19). Finally, rewards influence the choice of an animal (20,21). If different stimuli are associated with distinct rewards, then it is optimal to choose the one with the highest expected value (22,23). Neurons in the parietal and orbitofrontal cortex and also in the basal ganglia increase their activity for those stimuli that predict rewards that are larger or more probable (21,22,(24)(25)(26).Intriguingly, reward value also influences neuronal activity in early visual cortex. Shuler and Bear (27) demonstrated that neurons in rat primary visual cortex predict the timing of reward delivery, even in a phase of the task when the cells are not driven by a visual stimulus. This result is remarkable because primary visual cortex (V1) neurons are usually thought to code low-level visual features rather than stimulus value. Moreover, a functional magnetic resonance imaging (fMRI) study by Serences (28) demonstrated that reward value also influences V1 activity in humans. Subjects chose between two stimuli, and the one that was more rewarding evoked more activity. Apparently, the effects of reward value can reach back to the earliest cortical processing levels, where they might influence the coding of low-level features. However, the precise me...

No abstract

How do you make a decision if you do not know the rules of the game? Models of sensory decision-making suggest that choices are slow if evidence is weak, but they may only apply if the subject knows the task rules. Here, we asked how the learning of a new rule influences neuronal activity in the visual (area V1) and frontal cortex (area FEF) of monkeys. We devised a new icon-selection task. On each day, the monkeys saw 2 new icons (small pictures) and learned which one was relevant. We rewarded eye movements to a saccade target connected to the relevant icon with a curve. Neurons in visual and frontal cortex coded the monkey's choice, because the representation of the selected curve was enhanced. Learning delayed the neuronal selection signals and we uncovered the cause of this delay in V1, where learning to select the relevant icon caused an early suppression of surrounding image elements. These results demonstrate that the learning of a new rule causes a transition from fast and random decisions to a more considerate strategy that takes additional time and they reveal the contribution of visual and frontal cortex to the learning process.