Alpha rhythm
From EEGpedia
- Frequency: 8-13 Hz
- Posterior dominant
- Amplitude: 10-80 microV
- Wax and wane in amplitude
- Most prominent with eyes closed and relaxed
- Suppressed with eyes open, mental stress or sleep
- Left-right difference <1 Hz in frequency and <50% in amplitude (amplitude is usually higher on the right side)
- Alpha variants are normal sub- and supraharmonic frequencies of the alpha rhythm, particularly in children and young adults (Slow alpha variant and Fast alpha variant)
- 2-5% of healthy people does not have a detectable alpha rhythm
- The posterior basic rhythm frequency is age dependent:
| Age | Frequency |
|---|---|
| 0-3 months | No posterior basic rhythm |
| 4 months | 3-4 Hz |
| 5 months | 5 Hz |
| 1 year | 6-7 Hz |
| 3 years | 8 Hz |
| 7 years | 9 Hz |
| > 60 years | Decrease by 0.08 Hz/year |
Alpha rhythm of 9 Hz, posterior dominant with waxing and waning (source)
