Nerve cells communicating at a synapse. The brain neurons carry electrical signals called action potentials, via synapses. This activity occurs during mental states where the mind is active such as thinking or meditation, and even during sleep, as dreaming. Also under hypnosis . Normal wakefulness and the mind operates in a Beta range of frequencies (14 -21 cycles per second). During meditation and hypnosis the brain wave frequencies slow to Alpha (7 - 14 cycles per second). When dreaming, the brain is in Theta (3-8 Hz) or Delta (0.1-3Hz).