Exploring the relationship between the neural signatures of perceptual decision-formation and metacognition

Computational modelling and neurophysiological recordings suggest that perceptual decision-making involves integrating noisy sensory evidence up to an action-triggering threshold. The same process also plays a direct role in informing representations of choice confidence but the exact relationship remains unclear. Here, participants performed two versions of a random dot motion discrimination task in which kinematograms were presented at pseudo-random intervals. Analyses centered on three neural signatures of decision formation. Firstly, the Centro-Parietal Positivity exhibited a gradual build-up during coherent motion presentation and the amplitude reached at response cue presentation and at response execution both exhibited a strong positive correlation with confidence reports and choice accuracy. Second, higher choice confidence was associated with reduced preparation of the unchosen effector, while the chosen effector reached a fixed threshold at response irrespective of stimulus duration, RT or certainty. Thirdly, higher Fronto-Central Theta was observed on low confidence trials, consistent with models in which choice certainty reflects the relative activation of the chosen and unchosen response alternatives. These results suggest the neural representation of cumulative evidence and response conflict provide the necessary information for the emergence of graded representation of choice certainty and provide support for the neural mechanisms posited by these frameworks.