Preparing for saliencies: Emotional expectations under probabilistically and aversively salient situations

In humans, the expectation process in decision making has not been as thoroughly investigated as the evaluation process. The present study focused on the interaction between probabilistic saliency and motivational saliency during expectation and evaluation periods using stimulus-preceding negativity (SPN) and reward positivity (RewP). Twenty healthy participants performed a modified monetary-incentive delay task under reward-approach and punishment-avoidance conditions. Each condition was characterized by the likely outcome (reward only, punishment only) to manipulate motivational saliency. The task difficulty was regulated to control for probabilistic saliency, and the error trial was set as a probabilistically salient event (75% correct, 25% error). The results demonstrated that there was a larger SPN in the 25%-error trial than the 75%-correct trial and that it was left hemisphere predominant. Furthermore, there was an interaction between probabilistic and motivational saliency such that the SPN in the error trial was larger in the punishment-avoidance than in the reward-approach condition at Fz and at the right hemisphere. In contrast, RewP was only significantly different from zero in the 75%-correct trial in the reward-approach condition. These results confirm that the SPN increases with probabilistic saliency and that probabilistically salient events may intervene in the motivational saliency of the outcome; furthermore, that RewP reflects the weighted positive value of the outcome for reward but not the weighted negative value of the outcome for punishment. We discuss the interaction between probabilistic saliency and motivational saliency on SPN and its left hemisphere predominance based on the functions of the insular cortex.