Intermediate
Technical
IVT
delta rhythm
Slow EEG activity below 4 Hz, normally seen in deep sleep but pathological when present during wakefulness.
Full Definition
Delta rhythm refers to the slowest EEG frequencies, typically below 4 Hz, which normally characterize stages 3 and 4 of non-REM sleep (slow-wave sleep). In awake adults, the presence of delta activity is generally pathological, indicating severe brain dysfunction such as encephalopathy, structural lesions, or metabolic disorders. Delta waves are the predominant rhythm in newborns and gradually decrease as the brain matures.
Usage
Usage note: Often indicates pathology when present in awake states; normal in deep sleep.
In Context
- "Continuous delta rhythm during wakefulness indicated severe encephalopathy." — Critical care EEG report
- "Normal delta rhythm dominated the recording during deep sleep stages." — Sleep study documentation
Also known as
delta activity
delta waves
slow waves
Contrasted with
beta rhythm
gamma rhythm
Don't confuse with
theta rhythm
slow background