RT Journal Article SR Electronic T1 Responding to Unfair Offers Made by a Friend: Neuroelectrical Activity Changes in the Anterior Medial Prefrontal Cortex JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 15569 OP 15574 DO 10.1523/JNEUROSCI.1253-11.2011 VO 31 IS 43 A1 Campanhã, Camila A1 Minati, Ludovico A1 Fregni, Felipe A1 Boggio, Paulo S. YR 2011 UL http://www.jneurosci.org/content/31/43/15569.abstract AB When receiving unfair monetary offers from another person, the most common response is punishment. Existing literature on the Ultimatum Game indicates that individuals frequently refuse unfair offers even when this results in a loss for themselves. Here, we present behavioral and neurophysiological evidence demonstrating that friendship substantially modifies this response. When the proposer was a friend rather than an unknown person, unfair offers were less frequently rejected and the medial frontal negativity (MFN) typically associated with unfair offers was reversed to positive polarity. The underlying generators were located in inferior-mesial and right inferior- and medial-lateral frontal regions (BA10 and BA11). These findings highlight the fundamental role of the anterior prefrontal cortex in interpersonal economic interaction and, particularly, present new evidence on the effects of social distance on the MFN.