ORGANIZATION OF SENSORIMOTOR STAGES IN MA N - AN ERP STUDY

The main aim of this study was to test the relative organization of th ree of the stages of Sanders' 1990 information processing model: ''fea tures extraction'', ''response choice'', and ''motor adjustement''. Th e variables influencing these stages: stimulus degradation, stimulus-r esponse (SR) compatibility and preparatory period have been manipulate d. Event related potentials (N100, N200, P300) and reaction rime were recorded from ten healthy subjects, in a dichotic listening task. Reac tion times are lengthened for degraded stimuli, in the absence of a pr eparatory period and for SR non compatible conditions, However, the in teraction between preparatory period and stimulus degradation variable s, suggests an overlaping of the corresponding stages contrary to Sand ers' postulate. The non compatible condition increases the latency of N200 and P300 components. The results suggest that the response choice processing would be contemporary to the N200 component. They are disc ussed within the framework of models of early communication between se nsory and motor systems.