Reward expectation yields distinct effects on sensory processing and decision making in the human brain

Abstract

Reward expectation robustly guides both attention and decisions. Yet, whether common or distinct mechanisms mediate each of these processes remains unknown. Previous studies have often conflated the effect of reward expectation on sensory processing and decision-making because locations selected for sensory prioritization (sensitivity effects) were also prioritized for decisions (criterion effects). Here, we identify distinct forms of reward expectation that separably control spatial attention and decisional biases in human cortex. Sensitivity and criterion were independently modulated when expected rewards varied across locations (“space-specific”) or choices (“choice-specific”), respectively. Only sensitivity, not criterion, modulations reflected a limited, conserved attentional resource. Established neural and physiological signatures of attention, including gain modulation of event-related potentials, alpha-band power lateralization, and eye-movement biases, were elicited only by space-specific reward modulation. By contrast, neural correlates of decisional biases, including pre-stimulus alpha power suppression, selectively accompanied choice-specific reward modulation. Attention-related neural markers predicted sensitivity modulation by space-specific reward expectation but not criterion modulation by choice-specific reward expectation, indicating their distinct underlying mechanisms. Our findings uncover fundamentally dissociable behavioral and neural underpinnings of reward expectation effects on sensory and decisional selection, with critical implications for understanding how reward, attention, and choice are linked in the human brain. they must also choose to act quickly and pick off this fruit, to thwart their conspecifics. In other words, reward expectation can influence not only how attention is engaged but also how choices are made. Yet, these two effects have been frequently conflated in laboratory tasks. Here, with a task that decouples reward expectation’s effects on attention from those on decision-making we uncover their distinct neural correlates. Our results show how reward shapes attention and biases choices independently in the human brain.