Résumé : Non-averaged scalp-recorded human brain potentials were analyzed during selective attention to somatic (finger) sensory stimuli. Distinct cognitive electrogeneses were identified by numerical assessment of their scalp topographical congruities with appropriate templates. The P300 electrogenesis and the 40 Hz neuronal oscillations disclosed, at different scalp sites, variations in timing from trial to trial. However, in any given single trial the transient 40 Hz phase-locking between the somatic prefrontal and parietal subareas was found to be disrupted at P300 onset. The results suggest that the P300 cognitive electrogenesis manifests an inhibition of the neurons assemblies involved in the perceptual processing of the attended sensory input, thereby achieving a 'closure' of the cognitive operations dealing with the currently attended sensory input. P300 can thus be viewed as one of the physiological mechanisms which can control the kinetics of the 40 Hz binding process.