Frontal midline theta rhythm in young healthy adults.

In this study, we examined the relationship between the frontal midline (Fm) theta rhythm that appears when a healthy subject is engaged in mental tasks and the theta rhythm which appears in the frontal region of healthy subjects during light drowsiness. The samples for this study were obtained from 465 EEGs of healthy Japan Air Self Defense Force personnel. The 39 who had frontal theta rhythm during light drowsiness were selected to be included in the theta group. For the control group, 34 subjects were randomly selected from the remaining 426 without frontal theta rhythm. When these subjects were reexamined, the rate of appearance of the frontal midline theta rhythm which appears during light drowsiness was 87.2% in the theta group and 0% in the control group. The rate of appearance of the Fm theta was 94.9% in the theta group and 3.0% in the control group. The two types of frontal theta rhythms closely resembled each other in frequency (94.6%) and distribution (83.8%). Except for the results of the hypomania (Ma) scores, there was no remarkable difference between the two groups when the MMPI was administered. The results of our study suggest that there is a close correlation between the frontal theta rhythm that appears during light drowsiness and the Fm theta.