Positive and Negative Reinforcement from Intracranial Stimulation in Pigeons

Abstract

SINCE the discovery of reinforcement by intracranial stimulation in rats¹, neural systems of reward and punishment have been investigated in a number of mammalian species (for example, in monkeys, cats, dogs, goats, dolphins, and man^2–7), but only one study⁸ using a non-mammalian species (goldfish) has been published. At least one theoretical account of self-stimulation⁹ relies on the notion that it depends on the simultaneous excitation of two functionally distinct, but anatomically contiguous, neuronal systems. Comparative studies might be expected to throw light on this hypothesis, because the functional systems involved need not necessarily be contiguous in all species. From this point of view, the restriction of previous investigations to the class of mammals is regrettable, because the areas that appear to be primarily involved in reward and punishment, the limbic system and the hypothalamus, have developed structurally very little through the evolution of mammals¹⁰.