Drowsiness versus midline theta of Ciganek versus frontal midline theta (FMT)

The following is from an  adult patient:

 In the page above, rhythmic theta waves appear at CZ-PZ. The patient is drowsy; the alpha rhythms attenuate, as does temporal EMG, and there are temporal theta waves during the last three seconds of the page. The waves at the vertex are typical of midline central theta of Ciganek, a benign rhythm which often appears during the early stages of drowsiness. It has no pathological significance. It is distinct from drowsiness because it is also seen during the alert state.

Electroencephalographic theta discharges in the midline - PubMed

Midline theta rhythm - PubMed

The following is a continuation of the above sequence of pages:

The rhythmic midline theta reappears on the page above, again during drowsiness.

All

The following pages represent a very alert state, with frequent lateral eye movements.  The rhythmic midline theta is once again apparent, albeit of low amplitude.

Benign Variants in the EEG - Electroencephalography (EEG): An Introductory Text and Atlas of Normal and Abnormal Findings in Adults, Children, and Infants - NCBI Bookshelf

Midline theta of Ciganek should be distinguished from frontal midline theta, where theta waves appear as the electrographic correlate of focused attention and working memory.

Frontal midline theta oscillations during mental arithmetic: effects of stress - PMC