Mr. Awnish Singh
Sleep Lab Manager, Neurology and Sleep Centre New Delhi
Certified Sleep Technologist by IBSM
Fig:1 Stage Wake (W) 30 sec epoch: In EEG channels, Alpha activity (red box) is present for more than 50% of the epoch. In this case alpha activity (red box) is present for 20sec. Low amplitude mixed frequency (green box) is present for 10 sec. Slow eye movements (yellow box) are seen in EOG channels.
Fig: 2 Stage Wake (W) 10 sec Epoch: This epoch shows the appearance of alpha activity in EEG channels (red box) in 10 sec epoch. This is useful to measure the frequency of alpha waves. Alpha waves have a frequency of 8hz (Count no. of peaks in 1 sec) in O1 EEG lead in above epoch (green box).
Fig: 3 Stage N1 30 sec Epoch: This is a challenging epoch. Alpha activity (red box) is present for first 15sec in EEG channels and low amplitude mixed frequency (LAMF) activity (green box) is present for last 15 sec. AASM manual for sleep scoring rules does not clarify this situation where alpha and LAMF activity occupy 50% of epoch each. In our lab we score it as Stage N1. Slow eye movements (yellow box) are seen in EOG channels.
Fig:4 Stage N1 30sec Epoch: In this Epoch EEG channels show low amplitude mixed frequency (LAMF) activity (red box) for more than 50% of the epoch in absence of sleep spindles or K-complexes.
AASM Rules for scoring Stage Wake: In EEG, Alpha activity should be present for more than 50% of the epoch. Blinks, rapid eye movements and reading eye movements may be present.
AASM Rules for scoring Stage N1: In EEG, alpha activity is replaced by LAMF activity for more than 50% of the epoch. Slow rolling eye movements may be present in EOG. Vertex sharp waves may be present in EEG.