You Do the Math: Coding of Bets and Outcomes in a Gambling Task in the Feedback-Related Negativity and P300 in Healthy Adults Jutta Peterburs 1,2 *, Boris Suchan 2 , Christian Bellebaum 2 1 Institute of Medical Psychology and Systems Neuroscience, University of Muenster, Muenster, Germany, 2 Institute of Cognitive Neuroscience, Department of Neuropsychology, Faculty of Psychology, Ruhr University Bochum, Bochum, Germany Abstract The feedback-related negativity (FRN) is an event-related potential (ERP) component associated with processing of performance feedback, with more negative amplitudes for losses relative to wins. The amplitude of the FRN following near misses, i.e. the experience of coming close to winning, is between the amplitude elicited by losses and wins. In gambling, however, outcome value may not always be obvious since initially placed bets need to be taken into account when evaluating wins or losses. It is still unclear if initial bet size is reflected in the FRN or the later P300 component. The present study applied a virtual card gambling task to investigate the sensitivity of FRN and P300 to the manipulation of outcome magnitude as implemented through the presence or absence of initial bets, resulting in wins, losses or ambivalent outcomes, with the latter representing losses with and wins without bets. The FRN was larger for trials with bets compared to trials without bets. Wins were associated with a smaller FRN than losses or ambivalent outcomes, while losses and ambivalent outcomes did not differ. P300 amplitudes were larger for trials without bets, and wins were associated with a larger P300 than losses or ambivalent outcomes. Crucially, P300 amplitudes were also smaller for ambivalent outcomes compared to losses. Thus, the different dimensions determining outcome value appear to be integrated in early and late stages of feedback processing. However, only at later stages reflected in the P300 were ambivalent outcomes with and without bet clearly distinguished from other outcomes. Citation: Peterburs J, Suchan B, Bellebaum C (2013) You Do the Math: Coding of Bets and Outcomes in a Gambling Task in the Feedback-Related Negativity and P300 in Healthy Adults. PLoS ONE 8(11): e81262. doi:10.1371/journal.pone.0081262 Editor: Jason Jeremy Sinclair Barton, University of British Columbia, Canada Received June 10, 2013; Accepted October 11, 2013; Published November 25, 2013 Copyright: ß 2013 Peterburs et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This research was funded by the Ministry of Innovation, Science and Research of the federal state of Nordrhein-Westfalen, Germany (Ministerium fu ¨r Innovation, Wissenschaft und Forschung des Landes Nordrhein-Westfalen; MIWF; grant number 334-4). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: jutta.peterburs@uni-muenster.de Introduction Feedback is essential for informing us about the outcome of our actions and about the success or failure of strategic behaviour and behavioural adaptations. Negative feedback usually signals failure and thus decreases the occurrence rate of preceding actions, while positive feedback commonly indicates success, hence increasing occurrence rate. Electrophysiological research applying electroencephalography (EEG) has identified an event-related potential (ERP) component specifically associated with feedback-processing, the feedback- related negativity (FRN), a negative deflection with frontocentral distribution occurring approximately 200 to 300 ms after onset of performance feedback [1–4]. The FRN has been shown to be larger when outcomes are unfavourable compared to favourable [5–7], and is thought to reflect phasic decreases in dopaminergic signals conveyed from the basal ganglia to the anterior cingulate cortex [2,8–10]. It has initially been argued that action outcomes are generally coded in a dichotomous manner in the FRN, i.e. as either signalling goal achievement or failure. For instance, feedback indicating an ‘‘even’’ draw, i.e. neither a win nor loss, has been shown to elicit an FRN comparable to that elicited by negative feedback [11,12]. Reward magnitude was not reflected in the FRN [12,13]. More recent studies which took into account subjective reward expectations, however, did report that the FRN reflected gradual deviations of (negative) outcomes from reward expecta- tions, this effect being most pronounced when feedback could actually be used for learning action-outcome contingencies [10,14–16]. In accordance with these findings, the FRN appears to be modulated by subjective outcome value in gambling tasks. The size of the FRN in response to near misses, i.e. the experience of coming close to winning, has been shown to be between full miss (direct loss) and win, although – objectively – the near miss outcome does not differ from a full miss [17]. In contrast, the P300, a positive centroparietal ERP component starting about 300 ms after onset of a visual stimulus, which is commonly associated with processes of decision making [18], attentional allocation [19] and stimulus evaluation [20], appears to be sensitive to objective outcome valence [21]. Indeed, the P300 has been shown to be larger for wins than for losses, while being similar for losses and near misses [10,17]. It has been argued that near misses are a potent tool in gambling, motivating gamblers to continue playing and to bet more money, thus likely contributing to the development of PLOS ONE | www.plosone.org 1 November 2013 | Volume 8 | Issue 11 | e81262