Understanding how the brain transforms sensory information into adapted motor behavior necessitates to track the flow of information in the brain space. One question of great importance is to what extend the various required cognitive operations overlap in time (can a response begin to be prepared before the end of stimulus evaluation?). Symmetrically, it is essential to understand what is the degree of localization of the elementary cognitive operations (Are the motor areas purely motor, or do they intervene also in sensory processing?). After a brief statement of the current theoretical questions, we will present some recent data regarding these issues. The general logic followed is the track the information flow backward, starting from the response up to the stimulus. We will then present some technical limitation hampering more precise investigations and conclude on the challenges for the next few years for real advancement on those topics