ELEMENTS OF NORMAL SLEEP ACTIVITY - POSTERIOR OCCIPITAL SHARP TRANSIENTS (POSTs)

Shape
Mono- or biphasic triangular waves.

Amplitude
30-50 µv

Frequency / duration
Variable, from 1 Hz to 4-6 Hz

Distribution
Occipital

Persistence
They may last up to few seconds, and are seen mainly in stages 1, 2 & 3 of NREM sleep

Synchrony
After 2 years of age, they are bisynchronous and symmetrical


Reference:

1. Erwin, CW, Somerville, ER and Radtke, RA. A review of electroencephalographic features of normal sleep. J. Clin. Neurophysiol. 1:253-274
2. Fisch BJ. Spehlmann’s EEG primer, Amsterdam: Elsevier, 3rd edition
3. Niedermeyer E, Lopes da Silva F. Electroencephalography: basic principles, clinical applications and related fields, Baltimore, Maryland: Williams and Wilkins, 4th edition