When a stimulus is associated with a reward, it becomes prioritized, and the allocation of attention to that stimulus increases. For low-level features, such as color, this reward-based allocation of attention can manifest early in time and as a faster and stronger shift of attention to targets with that color, as reflected by the N2pc (a parieto-occipital electrophysiological component peaking at ∼250 msec). It is unknown, however, if reward associations can similarly modulate attentional shifts to complex objects or object categories, or if reward-related modulation of attentional allocation to such stimuli would occur later in time or through a different mechanism. Here, we used magnetoencephalographic recordings in 24 participants to investigate how object categories with a reward association would modulate the shift of attention. On each trial, two colored squares were presented, one in a target color and the other in a distractor color, each with an embedded object. Participants searched for the target-colored square and performed a corner discrimination task. The embedded objects were from either a rewarded or non-rewarded category, and if a rewarded-category object were present within the target-colored square, participants could earn extra money for correct performance. We observed that when the target color contained an object from a rewarded versus a non-rewarded category, the neural shift of attention to the target was faster and of greater magnitude, although the rewarded objects were not relevant for correct task performance. These results suggest that reward associations of complex objects can rapidly modulate attentional allocation to a target.
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