Dynamic Neural Encoding of Prior Expectations and Auditory Evidence Drive Perceptual Decision-Making

Perceptual decision-making has been studied extensively as the integration of evidence over time. Yet how moment-to-moment fidelity of sensory encoding interacts with prior expectations in shaping our choices remains poorly understood—particularly in the auditory domain. Here we quantify how priors act at the stage of sensory encoding and how these fluctuations predict behaviour. In a human model-based EEG study, we augmented a canonical click-train evidence accumulation task with probabilistic cues to shape prior expectations and analysed all activity with trial-resolved linear encoding models. Probabilistic cues drove alpha-oscillatory EEG patterns and induced symmetric shifts in response bias but did not change temporal integration dynamics. Neural encoding strength in lateralised auditory cortex uniquely predicted single-trial choice and confidence beyond what was explained by evidence strength or cueing alone. These findings identify sensory encoding fidelity as a mechanistic, behaviourally relevant link between priors and perceptual choice, offering new understanding how neural noise and expectations jointly shape decisions under uncertainty.