[Interindividual variability of exogenous and endogenous auditory evoked potentials in a condition of voluntary attention].

The use of P300 in psychopathology raises the important problem of the constitution of reference normative data and of the high variability of auditive ERP's in controls. To handle better this problem, we recorded 86 control subjects, using an auditory oddball paradigm with motor response. We analyzed the successive components of the ERP's evoked by target and standard stimuli (N1, P2, N2, P3a, P3b and slow wave negativity). Our results underlined the role of age, sex and psychological factors on the ERP's interindividual variability: P3 amplitude decreased and its latency increased with age, while its topography was more frontal in the older than in the younger subjects. The P300 occurrence after standard stimuli and P3 amplitude after target stimuli were different according to sex. Moreover, P300 amplitude, latency and topography were related to the subject's anxiety level. Finally, our results also propose new description modes of ERP's relying on P3a and P3b relative peak amplitude (P300 with prominent P3a or P3b), topographical predominance (frontal or parietal P300) and duration of the late positive complex (brief or long-lasting P300). These data will improve the clinical use of P300.