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.
- The posterior basic rhythm frequency is age dependant:
- 0-3 months: No posterior basic rhythm
- 4 months: 3-4 Hz
- 5 months: 5 Hz
- 1 years: 6-7 Hz
- 3 years: 8 Hz
- 7 years: 9 Hz
- > 60 years: Decrease by 0.08 Hz/year
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