Abstract
The effects of learning schedules on operant behavior in rats administered lead were studied. Two groups of animals received 2mg/ml or 5mg/ml of lead acetate until 21 days of age while suckling, and directly in drinking water, after weaning, from 21 to 60 days of age.
Four learning schedules, continious reinforcement (CRF), fixed interval (FI), Sidman avoidance (SA) and negative fixed-interval (N-FI) were used as behavioral test.
After the 61st day, lever press learning patterns were examined, and both the revised acquisition rate [(number of acquisitions/desired number of reinforcements)×(number of acquisitions/total responses)×100] and the revised avoidance rate [(number of avoidances/desired number of reinforcements)×(number of avoidances/total responses)×100] were calculated for each one hour session. Five sessions were recorded for the SA schedule and 10 sessions for the other three types.
The results are as follows: 1. A CRF schedule is easily learned and no significant difference is seen between the learning patterns of controls and those groups administered lead. 2. Although the Sidman avoidance schedule is also easily learned, differences in avoidance acquisition between controls and experimental groups were found during the initial stages of the test sessions. The number of shocks received seems to be a better parameter to evaluate learning patterns than responses. 3. Although both FI and N-FI schedules are useful in evaluating lead toxicity in the central nervous system, the N-FI schedule has the advantage that no prior water deprivation is necessary. It is suggested that the revised acquisition rate and revised avoidance rate are better parameters than the responses to evaluate learning patterns for either of these two schedules.
