What is the typical frequency range for alpha rhythms observed in an EEG?

The typical frequency range for alpha rhythms observed in an EEG is 8-12 Hz. Alpha waves are predominant when a person is awake but relaxed and not processing much information, often occurring during quiet, resting states with closed eyes. These rhythms play a role in promoting calmness and relaxation while also being associated with states of low arousal and creative thinking.

Other frequencies observed in an EEG correspond to different brain states. For instance, delta waves (0.5-4 Hz) are associated with deep sleep, theta waves (4-7 Hz) occur during light sleep and deep relaxation, beta waves (12-30 Hz) are linked to active thinking, alertness, and focus, and gamma waves (30-50 Hz) are associated with higher-level cognitive processing and sensory perception. Understanding these ranges helps in interpreting EEG readings and identifying the state of an individual's brain activity.