Perceptual metacognition of human faces is causally supported by function of the lateral prefrontal cortex

Abstract Metacognitive visual awareness—the ability to know that one is having a particular visual experience—is thought to optimally guide behavior and help us accurately navigate our complex social environments. Yet the neural underpinnings of visual metacognition continue to be the subject of vigorous debate: While prior work identified correlations between perceptual metacognitive ability and the structure and function of lateral prefrontal cortex (LPFC), evidence for a causal role of this region in promoting metacognition is controversial—in fact, some question whether the prefrontal cortex plays any role in supporting conscious visual experiences. Moreover, whether LPFC function promotes metacognitive awareness of perceptual and emotional features of complex, yet ubiquitous socio-emotional face stimuli is unknown. Using model-based analyses following a causal intervention to LPFC in humans, we demonstrate that LPFC promotes metacognitive awareness of the orientation of emotional faces—although not of their emotional expressions. Effects were specific to metacognition, as LPFC perturbation did not alter stimulus discrimination performance. Collectively, these data support the causal involvement of the prefrontal cortex in metacognitive awareness, and indicate that the role of LPFC function in metacognition encompasses perceptual experiences of naturalistic social stimuli.