Skip to main content
Intermediate Technical IVT

alpha rhythm

A normal EEG wave pattern of 8-13 Hz frequency, typically seen in the posterior regions during relaxed wakefulness with eyes closed.

Full Definition

Alpha rhythm is the dominant background rhythm in normal adult EEGs, characterized by sinusoidal waves of 8-13 Hz frequency and 20-200 microvolts amplitude. It is most prominent over the posterior head regions (occipital and parietal areas) and appears when the patient is awake, relaxed, and has their eyes closed. The rhythm typically attenuates or disappears when the eyes are opened or during mental concentration, a phenomenon known as alpha blocking. Alpha rhythm development begins in childhood and is considered a marker of normal brain maturation.

Usage

Usage note: Always specify frequency and location when describing alpha rhythm in reports.

In Context

  • "The EEG showed well-organized 10 Hz alpha rhythm over bilateral posterior regions." — EEG report
  • "Alpha rhythm reactivity was preserved with eye opening and closing." — Clinical assessment

Also known as

posterior dominant rhythm alpha waves

Contrasted with

beta rhythm theta rhythm delta rhythm

Don't confuse with

mu rhythm lambda waves
10-20 system ← Back to glossary amplitude asymmetry

Editors from these organisations have used our services since 1998

Reuters BBC Oxford University Press Penguin Random House Springer Microsoft Suncor Energy United Nations Fisher Investments IBM The Home Depot KODAK CHEVRON