What type of waves predominantly indicate drowsiness in EEG recordings of individuals?

Theta waves predominantly indicate drowsiness in EEG recordings. These waves typically range from 4 to 7 Hz and are commonly associated with the transition from wakefulness to sleep, particularly during lighter stages of sleep and relaxation states. When a person is drowsy, their brain activity shifts from the more alert alpha waves, usually seen when an individual is awake but relaxed, to theta waves that signal a deeper state of relaxation and the onset of sleep. This shift is crucial in determining the levels of consciousness, as theta waves become prominent when individuals are in a state of obscured awareness or are meditating or daydreaming. Recognizing these brainwave patterns is vital for EEG interpretation, especially in differentiating between various states of consciousness during clinical assessments.