[Diurnal variations of the composition of cognitive evoked potentials]

Auditory evoked potentials are recorded in 12 subjects 4 times per day: 08 30, 11 30, 14 30 and 18 30. The daily variations of N1, P2, N2 and P3 are studied globally and according to the (morning- or evening) type of subjects. The latency of N2 decreases during the day; it possibly reflects variations in vigilance. The P3 amplitude varies according to the subject typology: for morning-type subjects, P3 is higher in the afternoon than in the morning, and for evening-type subjects, P3 decreases from morning to evening. These evolutions possibly reflect the effort in attention required by different tasks.