Error effects in anterior cingulate cortex reverse when error likelihood is high

Abstract

Strong error-related activity in medial prefrontal cortex (mPFC) has been shown repeatedly with neuroimaging and event-related potential studies for the last several decades. Multiple theories have been proposed to account for error effects, including comparator models and conflict detection models, but the neural mechanisms that generate error signals remain in dispute. Typical studies use relatively low error rates, confounding the expectedness and the desirability of an error. Here we show with a gambling task and functional magnetic resonance imaging that when losses are more frequent than wins, the mPFC error effect disappears, and moreover, exhibits the opposite pattern by responding more strongly to unexpected wins than losses. These findings provide perspective on recent ERP studies and suggest that mPFC error effects result from a comparison between actual and expected outcomes.

Figure 1.

Onset and length of each trial and intertrial interval. An example choice from the LP condition is shown. After selecting an option, participants wait until the gamble display disappears and a blank screen is shown. This is followed by feedback indicating the outcome of the choice. Here, the participant chose the sure thing of 3 cents. This feedback is followed by another blank screen and then a fixation cross during the intertrial interval. The means for the pseudo-exponentially distributed gamble display and intertrial interval were 4.5 and 1.5 s, respectively.

Figure 2.

ACC significant clusters. Coronal (left) and sagittal (right) views of significant clusters of activation in the ACC for the interaction contrast between probability condition and outcome when choosing the risky option (red), the contrast between outcomes in the HP condition (yellow) which corresponds to the traditional paradigm used for testing the intended outcome discrepancy hypothesis, and where the two contrasts overlap (orange). X = 6, Y = 18, Z = 36, MNI coordinate space.

Figure 3.

Bar plots of regressors and their time courses of activation. Upper image, Bar plots for the four regressors in the ACC ROI identified using the interaction contrast: LP Condition Won and Lost (left side) and HP Condition Won and Lost. Bars representing Won are shown in red. The right side of the image corresponds with the traditional paradigm used for testing the intended outcome hypothesis. Error bars denote 95% confidence intervals. Lower image, Fitted activation time courses for the four regressors in the ACC ROI identified using the interaction contrast: LP Lost (blue), LP Won (green), HP Lost (red), HP Won (cyan). Error bars denote 95% confidence intervals.