Rewarding and Punishing Effects from Stimulating the Same Place in the Rat’s Brain
J. M. R. Delgado, W. W. Roberts, and N. E. Miller found that electrical stimulation in hypothalamic structures of the cat brain would motivate the learning and performance of escape and avoidance habits. J. Olds and Milner reported a positive reinforcing effect from electrically stimulating septal and hypothalamic areas in the rat’s brain. A potentiometer varied the voltage across a 100,000-ohm resistor in series with the rat’s brain. W. W. Roberts discovered areas in the posterior hypothalamus of cats in which electrical stimulation would motivate the cats to learn the correct turn in a Tone maze to escape the stimulation. One hypothesis that Roberts suggested to explain this odd effect was that the onset of stimulation in the structures may actually be rewarding, although it becomes punishing thereafter. The histology reveals that animals showing reward and escape learning had electrodes in the middle to anterior portion of the medial forebrain bundle, and it is possible that the fornix was involved.