Several accounts of anterior cingulated cortex (ACC) function currently exist - a conflict monitoring theory (e.g., Carter et al., 1998; Botvinick et al., 2001), a reinforcement learning theory (e.g., Holroyd & Coles, 2002), and an error-likelihood theory (Brown & Braver, 2005). The theories agree that the ACC is involved in error detection; however, the precise role of the ACC is still a subject of debate. In the conflict monitoring view, the ACC detects a conflict between intended and actual responses. In reinforcement learning view, the ACC is activated when events are worse-than-expected. In error-likelihood theory, the ACC stores information about error-likelihood. The results of the present research challenge the idea that the ACC performs conflict monitoring, and they are consistent with the idea that the ACC responds to worse-than-expected outcomes. The fMRI finding that the same region in the left dACC responds both to errors that people are aware of and to unexpected negative feedback is consistent with the reinforcement learning account and it is problematic for the conflict monitoring theory. The results of the present research also lead to reinterpretation of the findings taken to support the error-likelihood theory. In the present study, I develop a paradigm in which a memory task and a multiple object tracking tasks are combined. Participants receive feedback on the accuracy of their performance only after both tasks are completed. Negative feedback is ambiguous in terms of what type of error occurred (memory or tracking). After receiving negative feedback, participants are asked to interpret it. The behavioral results showed that most of the time the interpretations are correct (e.g. when participants make a memory error they indicate that they made a memory error); however, sometimes the interpretations are incorrect (e.g. when participants make a memory error they indicate that they made a tracking error). I assume here that participants interpret feedback correctly if they detect an error and they interpret feedback incorrectly if they miss an error.Contrasting all errors and correct trials, I identified a region within the left dACC responding greater to errors. A region of interest analysis revealed an interaction between error detection and phase of the trial: The region was more active to detected errors than undetected errors during task performance, but during feedback the pattern was reversed, such that the region was more active to undetected errors than to detected errors. The pattern is problematic for the conflict monitoring theory, because there is no conflict during feedback processing. The results are consistent with the reinforcement learning theory, since both error detection and processing of unexpected negative feedback are worse-than-expected outcomes.The imaging results also showed that an error related signal within the left dACC is content specific. Comparing the trials on which participants failed to retrieve correct information with the trials on which participants lost track of dots, I found that tracking errors lead to greater ACC activation. Several explanations are possible: One of them is that the ACC contains error-specific neurons similar to feature detectors in visual cortex. Alternatively, participants might have stronger expectations regarding the accuracy of their performance on tracking task than memory task; therefore, violations of stronger expectations result in greater ACC activation.
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