Music, Math, and Mind by David Sulzer

Author:David Sulzer [Sulzer, David]
Language: eng
Format: epub

Olds rigged a lever that the rat could push to “self-stimulate” by triggering electrical current from the tip of an electrode implanted in its own brain (figure 7.1). If the stimulation electrode were inserted into the region he identified, rats would press the lever two thousand times an hour for more than twenty-four hours straight. Indeed, their rate of lever pressing could progress from a starting exploratory rate of about ten per hour up to five thousand presses per hour. Remarkably, he noted that this learned behavior was decreased by chlorpromazine, the antipsychotic drug that Carlsson was contemporaneously reporting blocked dopamine receptors.

FIGURE 7.1  James Olds’s reward pathway

After noting that the animal would return to the same area of the cage, apparently to receive the electrical stimulus again, Olds made a simple device so that the animal could administer its own stimulus by pressing a lever. He determined regions of the brain where an electrical stimulus was most “rewarding” or “reinforcing,” that is, areas that would establish self-stimulation, and other regions where animals would quickly learn to avoid stimulating, that is, where the stimulus was “aversive.” The region identified that caused the greatest increase in stimulation was a bundle of fibers that disinhibited the activity of dopamine neurons.

Source: Art by John Langley Howard, from James Olds, “Pleasure Centers in the Brain,” Scientific American 195 (1956): 105–17.

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