Reversible Silencing of the Frontopolar Cortex Selectively Impairs Metacognitive Judgment on Non-experience in Primates.

Self-evaluation of one's own ignorance requires us to peer into our own mind retrospectively. Here, we found that only the bilateral frontopolar cortices (area 10) are recruited for metacognitive evaluation of non-experienced events in macaque monkeys performing metacognitive confidence judgment on memory under fMRI scanning and that targeted reversible inactivation of the localized spots in area 10 selectively impaired the confidence judgment of non-experienced events. In contrast, fMRI experiments revealed that area 10 was not recruited for metacognition of experienced events like the way that the dorsal prefrontal cortex (area 9) was and, correspondingly, the inactivation of area 10 did not impair confidence judgment of experienced events. Notably, this inactivation did not impair the ability to identify novel events by distinguishing from repetitive events. Our findings elucidate that the frontopolar cortex plays a causal role to confer not awareness of past experience in general but awareness of one's own ignorance.