Decision-making components and times revealed by the single-trial electroencephalogram

Decision-making stems from a sequence of information processing steps between the onset of the stimulus and the response. Despite extensive research, uncertainty remains about the actual cognitive sequence involved that leads to the reaction time. Using the hidden multivariate pattern method, we modeled the single-trial electroencephalogram of participants performing a decision task as a sequence of an unknown number of events estimated as trial-recurrent, time-varying, stable topographies. We provide evidence for five events occurring during participants' decision-making with two visual encoding events and three events capturing respectively attention orientation, decision, and motor execution. This interpretation is supported by the observation that a targeted manipulation of stimulus intensity yields Piéron's law in the interval between encoding and attention orientation, and Fechner's law in the interval between attention orientation and decision commitment. The final decision-related event is represented in the brain as a ramping signal in parietal areas whose timing, amplitude, and build-up predict the participants' decision accuracy.