The modulatory impact of reward and attention on global feature selection in human visual cortex

Abstract

Reward powerfully influences human behaviour and perception, with reward effects being observed already on the level of basic sensory processing. Although reward-related modulations generally resemble those related to attentional selection, it is debated whether these effects indeed reflect the same selection operations. Here we focus on neuromagnetic indices of global colour-based attention in visual cortex, and ask whether reward elicits the same or separable underlying modulation effects. Observers performed a colour/orientation selection task where colour served to define the target as well as reward prospect. On each trial a target containing the target colour and one other colour was presented in the left visual field (VF) together with a bicoloured distractor in the right VF. Reward was delivered on correctly performed trials when the reward colour appeared in the target but not when it appeared in the distractor. The effect of global colour selection was assessed by comparing the brain response to the distractor depending on whether it contained the target colour, the reward colour, both, or neither. We observed that both the reward and target colour led to similar increases of the neuromagnetic response between ~200–260 ms originating from the same ventral extrastriate visual cortex areas, albeit slightly temporally lagged. Importantly, the response to the target and reward colour alone always added up to match the response size of their combined presentation. These results suggest that while reward and attention recruit the same global feature selection effects in extrastriate visual cortex, they are likely controlled by independent top-down influences.