EFFECTS OF HALOPERIDOL IN A VARIABLE REINFORCEMENT ENVIRONMENT

Abstract

Recent studies have shown that pigeons' choice behavior adapts rapidly to dynamic changes in the reinforcing environment. This situation is an ideal one to assess the effects of neuroleptics that are supposed to affect the organism's sensorimotor capabilities, and therefore, its adaptation to variable reinforcement. This idea was evaluated in a choice situation where two levers provided a reinforcement ratio that changed seven times within each session in random order and without any signal. After 119 days in which twenty-two rats responded for food in this situation, the effects of four doses of haloperidol (0.04, 0.08, 0.16, & 0.24 mg/kg) were evaluated over a twelve-day periodo The drug did not interfere with the rats' adaptation to dynamic changes in the reinforcement ratio, but the response output decreased with the highest doses (0.16 and 0.24 mg/kg) of haloperidol. The discrimination that the rats established between the rich and the poor lever was not affected by haloperidol.

The parameters s and b ofthe generalized matching law (Baum, 1974) indicated that sensitivity to reinforcement was not eliminated by haloperidol, but that bias for the left lever was modified by the drug. Overall, the data suggest that haloperidol interferes with the motor system.