4-5 C/SEC RHYTHM

A series of forty subjects, twenty-eight males and twelve females, with the 4-5 c/sec rhythm is described. This 4-5 c/sec rhythm is characterized by the following: rhythmic 4-5 c/sec waves with amplitudes from 20 to 120 μV, regularly in the occipital and temporal regions; blocked by eye opening; immediately after eye closing there is a short group or a long train of alpha waves, which are then replaced by the 4-5 c/sec rhythm; it can easily be disturbed by acoustic, tactile or visual stimuli; it disappears during drowsiness and sleep and reappears only when the individual is completely awake. The 4-5 c/sec rhythm is a constant personal characteristic; diagnosis becomes possible after the first decade of life. The estimated frequency of trait carriers among the population examined in EEG laboratories is 0.025-0.075%. The trait seems to become rarer with advancing age and there is some indirect evidence that it might disappear some time during adult life. Two pairs of monozygotic twins were observed who showed complete concordance. In four out of forty siblings of propositi, the 4-5 c/sec rhythm was also present, but not in their parents or children. These results may suggest a genetic basis at least in a few, but do not confirm the assumption of a simple Mendelian mode of inheritance. The medical history of some cases raises the question of a possible exogenous causation (phenocopies), but no consistent pattern emerges. Reports pointing to a higher incidence of psychological abnormalities are confirmed. © 1969.