P 149. DLPFC is involved in perceptual decision-making but not metacognitive evaluation

Abstract

Growing evidence suggests that dorsolateral prefrontal cortex (DLPFC) plays a significant role in perceptual decision-making by integrating sensory evidence for different alternatives. This leads us to wonder whether the same information is used for metacognitive evaluation (e.g. confidence) of the decisions we make. After all, the two processes – decisions and their evaluations – are closely related under normal circumstances and thus it is possible that their underlying neural mechanisms are also widely overlapping. To clarify the role of DLPFC in perceptual decision-making and metacognitive evaluation we used off-line repetitive transcranial magnetic stimulation (rTMS). Subjects completed a visual categorization task and gave confidence ratings for the decisions they made. We also introduced extra information into the system by priming the stimuli. Priming is well known to increase objective as well as subjective measures of performance. If DLPFC incorporates this extra information into its processes a differential effect of TMS can be expected for primed stimuli. The results show that TMS clearly affected categorization performance. Subjects had more difficulty categorizing the stimuli correctly after rTMS to the right DLPFC. However, there was no effect of TMS for confidence ratings. The expected priming effect was only observed for repeated stimuli. Thus, our findings confirm that DLPFC is directly involved in perceptual decision-making. Since we did not find an effect of TMS on confidence ratings, our results suggest that metacognitive evaluation of decisions is a separate process which has its neurobiological correlates in other areas distinct from the DLPFC.