先行経験の違いがラットの衝動性の指標に及ぼす影響 <論文>

In the adjusting delay task, the degree of impulsive choice in rodents is measured. Large later reinforcement (LLR) and small sooner reinforcement (SSR) are presented in this task, and the length of delay for the LLR is adjusted according to the subjects’ choice. The amount discrimination task (ADT) and delay discrimination task (DDT) are essential training exercises for the adjusting delay task. However, research suggests that performance on the adjusting delay task is affected by prior experience, such as these practice tasks. The objective of this study was to investigate the influence of the order of the two training tasks, ADT and DDT, on adjusting delay task performance in rats.

Group differences were analyzed between the ADT-DDT group (rats that experienced ADT followed by DDT) and DDT-ADT group (rats that experienced DDT followed by ADT) in adjusting delay task performance. The mean was calculated for the total number of delay steps, which ranged from 1 to 7, and the length of delay that occurred at each step (1, 2, 4, 8, 16, 32, 64 s).

Findings revealed that rats in the ADT-DDT condition demonstrated fewer delay steps than rats in the DDT-ADT condition at the beginning of the exercise. The ADT-DDT group also reported shorter delays than the DDT-ADT group at the beginning of the assessment. Preference for shorter delays within the ADT-DDT group was demonstrated at the very end of training and was reflected in adjusting delay task performance as SSR preference. This finding may have occurred due to the close proximity of DDT training to the adjusting delay task.

In summary, the present study suggests that the order of training exercises for the adjusting delay task has a significant effect on performance. Specifically, ADT should be completed before DDT. Overall, the results from our study support researches that found an effect of previous training tasks on adjusting delay task performance.