Temporally unconstrained decoding reveals consistent but time-varying stages of stimulus processing

In this paper, we propose a method to track trial-specific neural dynamics of stimulus processing and decision making with high temporal precision. By applying this novel method to a perceptual template-matching task, we tracked representational brain states associated with the cascade of neural processing, from early sensory areas to higher-order areas that are involved in integration and decision-making. We address a major limitation of the traditional decoding approach: that it relies on consistent timing of these processes over trials. Using a temporally unconstrained decoding analysis approach, we found that the timing of the cognitive processes involved in perceptual judgements can vary considerably over trials. This revealed that the sequence of processing states was consistent for all subjects and trials, even when the timing of these states varied. Furthermore, we found that the specific timing of states on each trial was related to the quality of performance over trials.