Abstract
Perceptual decision making is the process of making a judgment based on sensory information. Perceptual decisions are naturally accompanied by a sense of confidence in the accuracy of the decision. Although the neural correlates of perceptual decision making and confidence have been the subject of substantial research, it is controversial whether the two processes share the same neural circuits. We designed a functional MRI study to address this question. Twenty-five participants performed direction detection tasks of moving dots. We separated the decisional and confidence processes temporally by obtaining the confidence responses after the decision response was made. In addition, we decorrelated the fMRI regressors for the decision and confidence periods by collecting confidence on only 55% of all trials. We found that decision and confidence were associated with large overlapping areas of brain activity in MT+, IPS, FEF, iPCS, IFC, MFG, doral ACC, and anterior insula. However, even though there was a relatively small correlation between fMRI regressors for decision and confidence, it is possible that these results were affected by this correlation. Therefore, in a separate analysis, we first regressed out the influence of one regressor on the fMRI signal, and then re-computed the activations for the other regressor. The same overlapping regions remained robustly activated. Finally, we analyzed whether any brain regions were relatively more selective for decision vs. confidence. We found that confidence recruited a number of unique regions over and above the decision process such as aPFC, dlPFC, dACC, and TPJ. On the other hand, we found no regions that are directly associated with the decision process but not confidence. These results demonstrate that overall decision and confidence are processed in highly overlapping neural circuits, but that several regions are preferentially involved in confidence computation.