Soma Shogo, Suematsu Naofumi, Yoshida Junichi, Ríos Alain, Shimegi Satoshi
Graduate School of Medicine, Osaka University, Toyonaka, Osaka, 560-0043, Japan; Brain Science Institute, Tamagawa University, Machida, Tokyo, 194-8610, Japan.
Graduate School of Medicine, Osaka University, Toyonaka, Osaka, 560-0043, Japan.
Behav Processes. 2018 Dec;157:291-300. doi: 10.1016/j.beproc.2018.10.014. Epub 2018 Oct 23.
As training progresses, animals show a transition from goal-dependent behavior to goal-independent behavior (habitual responses). Habit formation is influenced by several factors, including the amount of training and action-outcome contingency. However, it remains unknown whether and how discretion for behavioral selection influences habit formation. To this end, we trained male rats in two types of two-alternative forced-choice task: visual association and nonvisual association tasks. In the first type of task, rats learned the association between reward and a visual cue, the position of which was randomly changed per trial so that rats had to make a judgmental decision about which choice delivered the reward in each trial (discreet judgment group); in the second type of task, the rats learned that a reward was delivered after either choice following task initiation (uncontrolled judgment group). To test the sensitivity to contingency manipulation, the extinction tests were conducted in short- and long-term trained groups, with the result that the overtrained rats in the uncontrolled judgment group, but not the other three groups, showed less sensitivity. To further investigate the reward sensitivity in the long-term trained groups from another perspective, we continuously and periodically altered the reward size for each trial. The rats of the discreet judgment group changed intertrial intervals depending on reward size, while this tendency was weaker in the uncontrolled judgment group. These results suggest that discreet judgment maintained goal-directed rat behavior, whereas uncontrolled judgment led to the development of habit-like behavior.
随着训练的进行，动物表现出从目标依赖行为向目标独立行为（习惯性反应）的转变。习惯形成受多种因素影响，包括训练量和行动-结果的偶然性。然而，行为选择的自主性是否以及如何影响习惯形成仍不清楚。为此，我们在两种双选强制选择任务中训练雄性大鼠：视觉关联任务和非视觉关联任务。在第一种任务类型中，大鼠学习奖励与视觉线索之间的关联，每次试验中视觉线索的位置随机变化，因此大鼠必须在每次试验中对哪个选择能获得奖励做出判断性决定（审慎判断组）；在第二种任务类型中，大鼠学习到任务开始后无论做出哪种选择都会给予奖励（无控制判断组）。为了测试对偶然性操纵的敏感性，在短期和长期训练组中进行了消退测试，结果发现无控制判断组中过度训练的大鼠表现出较低的敏感性，而其他三组则没有。为了从另一个角度进一步研究长期训练组中的奖励敏感性，我们在每次试验中持续且周期性地改变奖励大小。审慎判断组的大鼠根据奖励大小改变试验间隔时间，而在无控制判断组中这种趋势较弱。这些结果表明，审慎判断维持了大鼠的目标导向行为，而无控制判断导致了类似习惯行为的发展。
