Annekathrin Schacht, Nele Adler, Peiyao Chen, Taomei Guo, and Werner Sommer (2012)

Association with positive outcome induces early effects in event-related brain potentials.

Biological Psychology, 89(1):130 - 136.

Emotional pictures, faces, or words elicit an early posterior negativity (EPN) in the event-related potential, starting around 200–400 ms, followed by a late positive complex (LPC). Occasionally, also very early effects of emotion (VEEEs) are seen prior to 200 ms. The present study examined whether VEEEs can be due to direct links established by reinforcement learning. In the learning session, participants learned to associate previously unknown Chinese words with monetary gain, loss, or neither. In the test session, they were required to distinguish the learned stimuli from novel distracters. Specific to stimuli associated with positive outcome a VEEE, consisting of a posterior positivity, appeared around 150 ms and an LPC between 550 and 700 ms, whereas an EPN was absent. These results show that previous association with reward can induce VEEEs, indicating that emotion effects in ERPs may arise in the absence of biologically preparedness and semantic meaning.