Expectancy and response strategy in a three-choice visual task

We investigated the relationship between sensorial discrimination and motor response by means of movement-related potentials, in a task where subjects had to discriminate between 3 Stimuli presented visually in a random way. The results indicate that subjects anticipate the response to each type of stimulus by following a probabilistic criterion in the absence of a warning stimulus. This criterion entails an erroneous lateralization of cerebral activation and a significant increase in reaction time, despite the reduction of errors.