THE EFFECT OF PHENOBARBITAL ON RATE OF FORGETTING AND PROACTIVE-INTERFERENCE IN DELAYED MATCHING-TO-SAMPLE

The barbiturate phenobarbital impairs the performance of nonhumans in delayed matching-to-sample procedures. In the present study, the perfo rmance of pigeons in a delayed matching-to-sample task was examined as a function of dose level of intraperitoneal phenobarbital administrat ion. Percent-correct matching accuracy decreased with increasing delay -interval duration to a greater extent under 20- and 30-mg/kg doses of phenobarbital than for vehicle control and 10-mg/kg conditions. That is, phenobarbital accentuated rate of forgetting. Rate of forgetting w as also assessed in terms of the rate parameter of negative exponentia l functions fitted to discriminability measures for different delay in tervals, thus allowing a separation of memorial from attentional influ ences. Proactive interference was evident as a greater rate of forgett ing for trials in which the sample stimulus to be remembered differed from that on the preceding trial, compared with trials in which the co nsecutive sample stimuli were the same. Increasing dose levels of phen obarbital attenuated proactive interference. Phenobarbital therefore i mpairs memorial function and limits the influence of information gaine d from previous trials in guiding or steering performance on the curre nt trial.