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dopamine, so drugs and electrical self-stimulation have many of the same effects. Neurotransmitters, including dopamine, and their role in the brain are discussed in more detail in the next chapters.
Works in Humans, Too
    Experiments of this type are not done in humans for ethical reasons, unless there is a patient with some severe and debilitating disorder that has not responded to other treatments. Dr. Robert Heath and his colleagues at Tulane in New Orleans put electrodes into the brains of human patients in the 1950s, and they had several important goals. They wanted to cure or ameliorate severe mental illness by direct electrical stimulation of the so-called pleasure centers. At that time, there were few treatment options for such patients.
    In an interesting case, one of Heath’s patients self-stimulated the septal region of his brain about 1,500 times per hour, showing thatthis can be a powerful and even consuming effect—this brings to mind the heroin addict quoted in the first paragraph of this chapter. The patient was reminded of and discussed sex during the stimulations. When stimulations were in a different region, the midbrain, the patient had happy thoughts that were not sexual. Other studies resulted in patients describing many different sensations and feelings, such as general pleasure, a sense of well-being, a positive change in mood, pleasant sensations in various body parts, relief from anxiety, and euphoria. What an amazing result!
    Overall, the work of Heath and others indicated that there were pleasure or rewarding centers in humans’ brains and in animals’ brains as shown by Olds and Milner. The notion that the brain is the organ of pleasure as well as pain was here to stay.
Deep Brain Stimulation Today
    A useful procedure used today in humans is called deep brain stimulation (DBS), which is not necessarily associated with drugs and pleasure. In this procedure, neurosurgeons implant electrodes into the brains of patients with a battery-powered generator that produces electrical pulses (see Figure 3-2 ). It has been found that stimulation of the electrodes can relieve symptoms of chronic pain, major depression, Parkinson’s disease, and other disorders. Of course, it depends where the electrodes are implanted, and different sites are used for different disorders. This treatment is relatively new because the first use for DBS was approved by the FDA in only 1997. It is interesting that the mechanism of DBS is still not thoroughly understood. It won’t surprise you to learn that DBS is being discussed as a treatment for addictive disorders. Promising results have been obtained in animal studies where DBS seems to reduce an animal’s interest in self-administering drugs.
    Figure 3-2. Deep brain stimulation is an important therapeutic technique used today that can treat serious neurological disorders. An electrode is placed in the brain region (the thalamus is shown here) that has been found to alleviate certain symptoms. A lead is attached to the electrode and the extension wires are threaded under the skin to a pulse generator that provides the stimulation. The pulse generator is placed under the skin in a region where it can be calibrated and serviced safely. The stimulator is turned on to alleviate various symptoms. (From http://www.medicinenet.com/script/main/art.asp?articlekey=56945 , with permission, accessed December 28, 2010.)

Stunning Implications
    Following the discovery by Olds and Milner, many thousands of papers have been published on the topic. Electrical stimulation reinforcement, as it came to be called, has been reported in many species examined including not only mammals, but also some fishes and even snails. It is often a robust and powerful effect. In one report, rats pressed levers for stimulation for almost 20 straight days, producing about 29 presses per minute! Self-stimulation has also been connected to food and water intake. At some sites in the brain, the rate