Section of Behavioral Neuroscience, Dept. of Cell Biology & Neurosciences, Istituto Superiore di Sanità, Rome, Italy.
Behav Brain Res. 2013 Nov 1;256:554-63. doi: 10.1016/j.bbr.2013.09.001. Epub 2013 Sep 7.
Individual differences in behavioural flexibility are a significant issue in human psychopathology as well as in its animal models. We aimed to investigate individual variations of operant-choice behaviour in the common marmoset (Callithrix jacchus), a small New World primate, using a new operant panel with two hand-poking holes.
Experimental subjects (N=16) were presented with a choice between a Small & Soon (SS) vs a Large & Late (LL) food reward. After extensive training (31 daily sessions with no delay, during which a basal, large-reward preference developed), the delay before release of LL was progressively increased (from 0 to 60 s, during 16 daily sessions; indifferent point at delay=9 s). Subjects were classified as either "flexible" or "non-flexible", respectively, based on a decrease (or not) in the preference for LL with increasing delays. Each subject was also classified as "maximizer" (or "non-maximizer") based on capacity (or not) to maximize the food payoff as delay increased.
Upon delays shorter than the indifferent point (<9s), none of the subjects showed a shift from LL to SS, denoting a lack of delay-induced, cognitive impulsivity. Individual differences only emerged upon delays longer than the indifferent point (>9 s), when a preference shift could be interpreted as economically-driven. In general, a profile of few unrewarded hand-pokes in reaction to initial delays (i.e., a low motor impulsivity) and of clear-cut basal LL preference seemed to predict elevated flexibility of choices and better food payoff, which was typical of subjects classified as both "flexible & maximizer".
These results provide normative data on the marmosets, which can be used as a model for the investigation of 1) individual differences in behavioural flexibility, as well as 2) biological mechanisms rooted in our evolutionary history.
个体行为灵活性差异是人类精神病理学及其动物模型中的一个重要问题。我们旨在通过使用带有两个手戳孔的新型操作面板，研究常见绒猴（Callithrix jacchus）的操作性选择行为的个体变化，这是一种小型新世界灵长类动物。
实验对象（N=16）在小而快（SS）与大而慢（LL）食物奖励之间进行选择。经过广泛的训练（31 个无延迟的日常课程，在此期间形成了基础的大奖励偏好），LL 的释放延迟逐渐增加（从 0 到 60 秒，共 16 个日常课程；无差异点延迟=9 秒）。根据随着延迟增加对 LL 的偏好是否减少（或不减少），分别将每个主体归类为“灵活”或“不灵活”。每个主体还根据其是否能够随着延迟增加而最大化食物收益（或不能）来归类为“最大化者”（或“非最大化者”）。
在短于无差异点的延迟（<9 秒）下，没有一个主体从 LL 转移到 SS，这表示没有因延迟引起的认知冲动。只有在长于无差异点的延迟（>9 秒）时，才能将偏好转移解释为经济驱动的。一般来说，在初始延迟时，很少出现无回报的手戳（即低运动冲动）和明确的基础 LL 偏好的特征，似乎可以预测选择的灵活性更高，并且食物收益更好，这是被归类为“灵活且最大化者”的主体的典型特征。
这些结果为绒猴提供了规范数据，可以将其用作研究 1）行为灵活性的个体差异以及 2）根植于我们进化史的生物学机制的模型。
