History of one's own performance modulates evaluative processing of another's action outcomes, but not vice versa.

In action monitoring, i.e., evaluating an outcome of our behavior, a reward prediction error signal is calculated as the difference between actual and predicted outcomes and is used to adjust future behavior. Previous studies demonstrate that this signal, which is reflected by an event-related brain potential called feedback-related negativity (FRN), occurs in response to not only one's own outcomes, but also those of others. However, it is still unknown if predictions of different actors' performance interact with each other. Thus, we investigated how predictions from one's own and another's performance history affect each other by manipulating the task difficulty for participants themselves and their partners independently. Pairs of participants performed a time estimation task, randomly switching the roles of actor and observer from trial to trial. Results show that the history of the other's performance did not modulate the amplitude of the FRN for the evaluation of one's own outcomes. In contrast, the amplitude of the observer FRN for the other's outcomes differed according to the frequency of one's own action outcomes. In conclusion, the monitoring system tracks the histories of one's own and observed outcomes separately and considers information related to one's own action outcomes to be more important.

Stimulus valence influences the evaluative processing of action outcome.

The aim of the current study is to reveal the influence of prior associations between feedback stimuli and outcomes, in everyday life, on the early and late evaluative processing of outcomes. Participants were subjected to a simple gambling task while their electroencephalograms were recorded. Over two conditions, participants received congruent and incongruent feedback stimuli during the task. Feedback stimuli previously associated with positive outcomes were paired with monetary gain in the congruent condition and paired with monetary loss in the incongruent condition. We analyzed feedback-related negativity and P300 event-related brain potentials, as indices of early and late outcome evaluation. The results show that monetary loss, compared to gain, elicited larger feedback-related negativity, irrespective of congruency. However, the feedback-related negativity effect was delayed in the incongruent condition and an increased P300 amplitude was observed for congruent-loss outcomes. The valence of stimuli formed through experiences differently modulate early and late processes of outcome evaluation. The present study emphasizes the need to consider the stimulus valence to understand processes of outcome evaluation.

Effect of p53 deficiency on external vascular cuff-induced neointima formation.

The p53 tumor suppressor gene may act as an inhibitor of vascular neointima formation in response to injury and in the present study the effects of p53 deficiency on external vascular cuff-induced neointima formation were evaluated. Vascular neointima formation was induced by an external vascular cuff; a polyethylene tube placed around a 2 mm segment of the left femoral artery ensheathed the adventitia, but avoided direct intraluminal injury. Two weeks after cuff placement, the cuff-sheathed and contralateral control arteries without cuff from wild-type (n=10) and p53 deficient (n=8) mice were harvested and analyzed by quantitative morphometry. The areas of the lumen, intima, and media were measured in 10 cross-sections from one edge to the other of the cuffed portion, and in the corresponding 2-mm segment of the contralateral control artery. The volume ratio of the intima to media (I/M) was calculated. The contralateral control arteries without a cuff did not have intima in either wild-type or p53 deficient mice. In the cuff-sheathed arteries, neointima formation of p53 deficient mice with an I/M of 93% was significantly greater than that of wild-type mice with an I/M of 50% (P=0.001). The absence of p53 is associated with increased neointima formation in response to cuff injury.