This is the first installment of the FTLOS (For The Love Of Science) series.
(More detail for those who are curious):
Stage One – Alert wakefulness.
Characterised by beta waves, typically greater than 13Hz. Stage Two – Relaxed wakefulness. Characterised by alpha waves, typically 8 – 13Hz. Stage Three – The first stage in NREM (N1) sleep. Characterised by theta waves, typically 3 – 7Hz. Stage Four – The second stage in NREM (N2). Characterised by theta waves, typically 12 – 14Hz. Stage Five – The third stage in NREM (N3). Characterised by delta waves, typically fewer than 4Hz. Stage Six – REM sleep. Characterised by “saw tooth” waves, which are random and low in voltage.
FTLOS: Stages Of Sleep – مراحل النوم