The wave and spike formations occur usually on the background of a normal basic cortical rhythm, are remarkably constant in their occurrence in a frequency range of 2.5-3.5 cycles per second, but show considerable variations in the position and amplitude of the spike component in the same record, and indeed within the same discharge. The wave and spike formations are seen most frequently during hyperventilation. Other paroxysmal disturbances occur in 50% of the records and the most frequent of these are single or multiple spiking discharges and paroxysmal bursts of 4-6-per-second activity. A surprisingly high incidence of wave and spike formation occurs after the age of 30 years.Abstract Teaser