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In the 1950s, the psychologists James Olds and Peter Milner modified the chamber so that a lever press would deliver direct brain stimulation through deep implanted electrodes. What resulted was perhaps the most dramatic experiment in the history of behavioral neuroscience: Rats would press the lever as many as 7,000 times per hour to stimulate their brains. This was a pleasure center, a reward circuit, the activation of which was much more powerful than any natural stimulus.
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I know what you're thinking:
What does it feel like for a human to have his or her medial forebrain reward circuitry stimulated with an electrode? Does it produce a crazy pleasure that's better than food or sex or sleep or even "Seinfeld" reruns? We do in fact know the answer to that question. The bad news, however, is that it comes, in part, from some deeply unethical experiments.
Patient B-19, a 24-year-old male homosexual of average intelligence who suffered from depression and obsessive-compulsive tendencies, was wheeled into the operating room. Electrodes were implanted at nine different sites in deep regions of his brain, and three months were allowed to pass after the surgery to allow for healing. Initially stimulation was delivered to all nine electrodes in turn. However, only the electrode implanted in the septum produced pleasurable sensations.
When Patient B-19 was finally allowed free access to the stimulator, he quickly began mashing the button like an 8-year-old playing Donkey Kong. According to the paper,
"During these sessions, B-19 stimulated himself to a point that, both behaviorally and introspectively, he was experiencing an almost overwhelming euphoria and elation and had to be disconnected despite his vigorous protests."
Lest anyone think that it is only men -- creatures of inherently base urges -- who would respond in this manner, another recorded case, performed by a different group, involved a woman who received an electrode implant in her thalamus, an adjacent deep brain structure, to control chronic pain. This technique has proven effective for some patients whose severe pain is not well-controlled by drugs. However, in this patient the stimulation spread to nearby brain structures, producing an intense pleasurable and sexual feeling:
"At its most frequent, the patient self-stimulated throughout the day, neglecting her personal hygiene and family commitments. A chronic ulceration developed at the tip of the finger used to adjust the amplitude dial and she frequently tampered with the device in an effort to increase the stimulation amplitude. At times she implored her family to limit her access to the stimulator, each time demanding its return after a short hiatus."
So, not to put too fine a point on it,
these patients responded just like Olds and Milner's rats. Given the chance, they would stimulate their pleasure circuits to the exclusion of all else.Back to patient B-19: Before his brain stimulation began, he was shown a "15 min long 'stag' film featuring sexual intercourse and related activities between a male and female." Not surprisingly, he was sexually indifferent to this material and even a bit angry about being made to view it.
Following pleasure circuit self-stimulation, however, he readily agreed to re-view the film," ... "and during its showing became sexually aroused, had an erection and masturbated to orgasm." All this in the decidedly unsexy environment of the lab.
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While it's clear that patient B-19 found the brain stimulation to be intensely pleasurable, I'm not convinced that he truly became heterosexual, even temporarily. It should also be cautioned that this report concerns only a single individual, not a population (with a control group).
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Many years later, experiments in both humans and critters have revealed that most experiences in our lives that we find transcendent -- whether illicit vices or socially sanctioned ritual and social practices as diverse as exercise, meditative prayer, or even charitable giving -- activate this pleasure circuit in the brain.
Shopping, orgasm, learning, highly caloric foods, gambling, prayer, dancing 'till you drop, and playing on the Internet: They all evoke neural signal that converge on this same brain circuit activated in Olds and Milner's rats and in Patient B-19. This dopamine-using pleasure circuitry can also be co-opted by some psychoactive substances, like cocaine, nicotine, heroin, marijuana or alcohol. Evolution has, in effect, hardwired us to catch a pleasure buzz from a wide variety of substances and experiences from crack to cannabis, from meditation to masturbation, from Bordeaux to beef.