ANOTHER HOLDER FOR CHRONICALLY IMPLANTED ELECTRODES

Overnight Performance Decrement with Intracranial Reinforcement

An overnight performance decrement is allegedly characteristic of habits maintained by intracranial electrical stimulation. The decrement was here found to be (a) not common to all electrode sites, (b) reduced by one un-reinforced trial, and (c) reduced by intracranial stimulation administered below a rewarding intensity. The electrode sites not associated with performance decrement were in the median forebrain bundle (MFB). Those associated with decrement were somewhat removed from the MFB, at sites other experiments have shown to be both positively and negatively reinforcing. These findings are discussed in relation to Deutsch's theory of simultaneous drive-induction and reinforcement.

Delayed punishment of positively reinforced bar presses

Combining positive and negative reinforcement (both being electrical stimulation of the brain) for lever pressing by 4 rats produced a gradient of suppression as the 2 qualities of reinforcement were separated temporally. Maximal suppression occurred with an interstimulus interval of about 1 sec. This maximum was interpreted as marking the intersection of a waning interaction of the neurological aspects of reward and punishment and a delay-of-punishment gradient. After the 1 sec. of neural interaction, the greater the delay of punishment the less the suppression of responding.

Intracranial Reinforcement Compared with Sugar-Water Reinforcement

Three ways in which electrical, intracranial reinforcement is reputed to differ from conventional reinforcement were tested in an experiment which equated the form of the responses being reinforced and the response-reinforcement relation. Four groups of rats performed instrumental or consummatory responses reinforced by intracranial reinforcement or sugar. In no comparison did the kind of reinforcement produce a difference, but in every comparison the kind of response reinforced did produce a difference. It is inferred that reputed differences between intracranial reinforcement and conventional reinforcement are artifacts.