Frontal Theta Rhythm Research Articles

Frontal Theta Rhythm: Evaluation of its Clinical Electrophysiological Significance with a View Point of Aging

Background: Frontal theta rhythms can be observed in routine electroencephalogram (EEG) examinations. Their significance has been interpreted from pathological or physiological viewpoints by many previous studies. We evaluated the clinical electrophysiological significance including aging of the frontal theta rhythms to differentiate pathological theta activities. Methods: Since 23 EEGs, out of 2,424 patients routinely taken in our hospital and 87 healthy volunteers, showed frontal theta rhythms during drowsiness, those subjects were re‐examined at rest and during a mental task. The morphological features of theta rhythms were compared between the two conditions and analyzed in terms of clinical conditions. Results: In 16 subjects theta rhythms either disappeared or were suppressed during the mental task (“suppressed” group). In the seven subjects theta rhythms recorded during drowsiness were equivalent or were activated by the mental task (“activated” group). The subjects of the suppressed group were found to have clinical findings suggesting cerebral organic changes, while those of the activated group did not have such findings. In the morphological comparison between these groups, the frequency, amplitude, and duration were significantly different. Conclusion: The differentiation of these two types of frontal theta rhythms may be possible by clinical information, morphological features of theta rhythms and their changes during a mental task. In the case of pathological theta rhythms appearing in middle and advanced age, they can sometimes be based on aging due to arteriosclerotic changes and others.

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.

The frontal theta rhythm (FmQ) as an EEG entity

The frontal theta rhythm (FmQ) as an EEG entity

A comparison of frontal theta rhythms induced by hyperventilation with those of mental work

A comparison of frontal theta rhythms induced by hyperventilation with those of mental work

4 c/sec vertex spindles

An EEG phenomenon consisting of thythmic 3.5–4.5 c/sec triangular waves an average amplitude of 40 μV, strictly localized at the vertex, occurring in spindles with an average duration of 2.5 sec has been observed in 20 patients. This phenomenon was called 4 c/sec spindles. It occurred particularly in awake adolescents with a peak at the age of 14–15 years. The most common diagnosis under which they had been referred was vasomotor instability. The EEGs of 30% of these patients moreover showed a frontal theta rhythm at 6–7 c/sec. In 90% of these patients the EEG was otherwise unremarkable.