Definition A brain oscillation pattern detected by EEG, which in humans is termed cortical theta rhythm and has a frequency in the 4 to 7 Hz range. Theta waves are normally present in minimal amounts in the temporal lobes.
The theta rhythm is common in young children. In older children and adults, it appears during light sleep, meditation and drowsiness, but not in deep sleep. There is an uptick of theta activity during short term memory tasks. It is actively sought in yoga and transcendental meditation.