Dependence between the P3-wave and the prestimulus EEG negative shift under conditions of probability prediction

The connection between the prestimulus slow potential shift (SPS) and the P3-wave of auditory averaged evoked potentials (AEP) from Fz and Cz is studied upon changing the probability and signal characteristics of the stimuli. It has been found that while the changes in the P3-wave, depending on the character of the experimental tasks, are unidirectional for all subjects studied in both recordings and repeat our earlier results, the changes in SPS have different directions. The same changes in P3 are accompanied in some cases by a slightly expressed negativization, in other cases by a certain positivization and in a third group of cases by lack of SPS. The results obtained show that the observed changed in the P3-wave under the conditions of our experiments are not connected with pre-stimulus SPS of the CNV type, being generated in the central nervous system irrespectively of them. They support our hypothesis that the P3-wave is connected with the processes of probability prediction in the brain functioning.