Abstract
Our subjective visual experience of the world comes with varying degrees of confidence in the things we see. Previous research indicates that different brain regions may facilitate our capacity for confidence, such as the lateral intraparietal area (Kiani & Shadlen, 2009), supplementary eye fields (Middlebrooks & Sommer, 2012), and pulvinar (Komura et al., 2013). Here, we investigated whether another part of the oculomotor control circuit, the superior colliculus (SC), also plays a role, and developed a novel task to investigate whether population-level activity in the SC reflects perceptual confidence, or simply predicts perceptual performance. Two rhesus macaques viewed random dot motion stimuli and reported the perceived direction of motion with eye movements. If monkeys chose correctly, they received a reward. On half of the trials, monkeys received an opt-out target option, which could be selected to receive a smaller but guaranteed reward; this choice is taken to reflect low subjective confidence. We first implemented logistic regression classification to determine if we could predict correct perceptual choices from neuronal activity in the SC. We found that decoding accuracy was greater on trials when the opt-out was available but waived, presumably reflecting high confidence. Critically, in our new task, we manipulated dot motion coherences to produce two conditions that had equivalent levels of performance (d') but different levels of confidence (i.e., probability of selecting the opt-out response). Results indicate that once performance is matched, population-level activity does not differ between high and low confidence conditions. These results support the hypothesis that SC activity primarily predicts perceptual performance rather than subjective confidence per se, and highlight an important methodological innovation for future investigations of perceptual confidence in other brain regions.
Meeting abstract presented at VSS 2017