Abstract
Perceptual decision making has several underlying components including stimulus encoding, perceptual categorization, response selection, and response execution. Evidence accumulation is believed to be the underlying mechanism of decision-making and plays a decisive role in determining response time. Previous studies in animals and humans have shown parietal cortex activity that exhibits characteristics of evidence accumulation in tasks requiring difficult perceptual categorization to reach a decision. In this study, we made use of a task where the challenge for the participants is to identify the stimulus and then from memory apply an abstract rule to select one of two possible actions. The task was designed so that stimulus identification was easy but response selection required cognitive computations and working memory. In simultaneous EEG recordings, we find a one-to-one relationship between the duration of the readiness potential observed prior to the response over motor areas, and decision-making time estimated by a drift-diffusion model of the response time distribution. This close relationship implies that the readiness potential reflects an evidence accumulation process for response selection, and supports the notion that evidence accumulation is a general neural implementation of decision-making. The evidence accumulation process that captures variability in decision-making time will depend on the location of the bottleneck in information processing.
