Abstract: An electric or electromagnetic field generator for therapeutic use. A heartbeat signal produced by a user is monitored to derive a signal indicative of the frequency of the user's heartbeat. A generator creates an electric or electromagnetic field based on a combined signal derived from a first signal dependent on the determined heartbeat frequency, and a second signal stimulating the brain activity of the user. The device may be worn by the user, on an ongoing basis. The second signal may be modified to provide a train of pulses having a width substantially equal to a neuron depolarization pulse to improve the user's response to the signal.