“Wanted!” The effects of reward on face recognition: electrophysiological correlates

The aim of the present study was to uncover the temporal dynamics of face recognition as a function of reward. Event-related
potentials (ERPs) were recorded during the encoding and the subsequent old/new memory test in response to faces that could
be associated with a monetary reward. The behavioral results showed that faces associated with reward at both encoding and
retrieval were recognized better than the unrewarded ones. ERP responses highlighted that successful encoding predictive of
subsequent memory was greater for faces associated with reward than for faces without reward-driven motivational learning.
At retrieval, an early positive-going component was elicited for potentially rewarded faces on frontal regions, while the
occipito-temporal N170 component showed priming effects as a function of reward. Later on, larger centro-parietal ERP components,
related to recognition memory, were found selectively for reward-associated faces. Remarkably, electrophysiological responses
varied in a graded manner, with the largest amplitude yielded by faces with double reward, followed by faces associated with
reward only at encoding. Taken together, the present data show that the processing of outcome expectations affects face structural
encoding and increases memory efficiency, yielding a robust and sustained modulation over frontal and temporal areas where
reward and memory mechanisms operate in conjunction.