Lateral inhibition in neural networks and the shape of EEG alpha rhythm waves.

Baseline EEG traces were recorded from the right occipital area with the eyes closed in 15 subjects. Rhythmic stimulation with bright, diffuse flashes of light was applied through the closed eyelids at specific points in the alpha-wave phase (trigger photic stimulation). Ten versions of stimulation were used, with application at different phases for 1 min at each phase. Responses occurring in conditions of stimulation in different phases were compared using the mean alpha wave amplitude in each version and the wave shape in terms of the level of asymmetry of the leading and trailing fronts. When flashes were delivered at the middle of the descending front of the potential (positivization), changes in wave shape were most marked and were very different from those seen in the other nine stimulation phases. This effect was most marked in subjects with low-amplitude alpha rhythms. These results suggest that the individual level of the alpha rhythm in a given subject and the dynamics of the wave shape can be explained by the characteristics of the structure of the system of recurrent-lateral inhibition.