States of Consciousness and Dreams.
Modern materialistic science is not sure about the origin and nature of most psychic phenomena including dreams. This information can be found in Vedic scriptures.
Srimad Bhagavatam 6.16.53-54, 7.7.25 or 7.15.61 describes three material states of consciousness:
1. jagrata, awakened state (beta, 14 - 20 Hz)
2. svapna, dreaming state (alfa, 7 - 14 Hz)
3. susupti, deep sleep (theta, 4 - 7 Hz)