TY - JOUR T1 - A Neural Signature Encoding Decisions under Perceptual Ambiguity JF - eneuro JO - eNeuro DO - 10.1523/ENEURO.0235-17.2017 SP - ENEURO.0235-17.2017 AU - Sai Sun AU - Rongjun Yu AU - Shuo Wang Y1 - 2017/11/14 UR - http://www.eneuro.org/content/early/2017/11/14/ENEURO.0235-17.2017.abstract N2 - People often make perceptual decisions with ambiguous information, but it remains unclear whether the brain has a common neural substrate that encodes various forms of perceptual ambiguity. Here we used three types of perceptually ambiguous stimuli as well as task instructions to examine the neural basis for both stimulus-driven and task-driven perceptual ambiguity. We identified a neural signature, the late positive potential (LPP), that encoded a general form of stimulus-driven perceptual ambiguity. In addition to stimulus-driven ambiguity, the LPP was also modulated by ambiguity in task instructions. To further specify the functional role of the LPP and elucidate the relationship between stimulus ambiguity, behavioral response, and the LPP, we employed regression models and found that the LPP was specifically associated with response latency and confidence rating, suggesting that the LPP encoded decisions under perceptual ambiguity. Lastly, direct behavioral ratings of stimulus and task ambiguity confirmed our neurophysiological findings, which could not be attributed to differences in eye movements either. Together, our findings argue for a common neural signature that encodes decisions under perceptual ambiguity, but is subject to the modulation of task ambiguity. Our results represent an essential first step towards a complete neural understanding of human perceptual decision making.Significance Statement Humans have a dedicated neural system to make decisions in ambiguous situations. Neuroimaging and electrophysiological studies have revealed brain regions and neural signatures in coding perceptual ambiguity, but it remains unknown whether there exists a common neural substrate that encodes various forms of perceptual ambiguity. Here we revealed a common neural signature, the LPP, that encoded decisions under perceptual ambiguity. Using task instructions with different levels of ambiguity, we further showed that this neural signature was modulated by task ambiguity. Our findings highlight a common neural substrate underlying perceptual decision-making under ambiguity. ER -