Infant rats can learn time intervals before the maturation of the striatum: evidence from odor fear conditioning
Infant rats can learn time intervals before the maturation of the striatum: evidence from odor fear conditioning
复制标题
DOI：
10.3389/fnbeh.2014.00176
复制
发表时间：
2014-05-15
影响因子：
3
通讯作者：
Mouly, Anne-Marie
中科院分区：
文献类型：
--
作者：
Boulanger-Bertolus, Julie;Hegoburu, Chloe;Mouly, Anne-Marie
间隔计时是指感知、估计和辨别秒到分钟范围内的持续时间的能力。目前对整个发育过程中间期计时的个体发育知之甚少。另一方面，尽管维持间隔计时的神经回路存在争议，但纹状体被认为是该系统的重要组成部分，其成熟发生在大鼠出生后第三周(PN)左右。本研究的总体目标是调查纹状体尚未成熟的年龄的间隔计时能力。我们使用了气味恐惧条件反射，因为它可以应用于非常年轻的动物。在气味恐惧条件反射中，气味被呈现给动物，并在固定的时间间隔后发出轻微的脚电击。成年大鼠已经被证明在几次联系之后学会了气味和电击之间的时间关系。本研究的第一个目的是使用2-脱氧葡萄糖放射自显影技术评估大鼠发育过程中嗅觉恐惧条件反射过程中纹状体的活动。数据显示，尽管在所有测试年龄都表现出恐惧学习，但在成年动物中观察到纹状体的激活，但在幼年动物中没有观察到。接下来，我们评估了在纹状体被纳入恐惧条件反射回路之前和之后的年龄中是否存在间隔计时的证据。我们使用了一种实验装置，允许同时记录成年大鼠的冻结和呼吸，这已被证明对间隔时间很敏感。这使得能够检测气味恐惧条件下12天PN婴儿的冻结和/或呼吸曲线与持续时间相关的模式。这表明，当婴儿的纹状体还不起作用时，他们能够像成年人一样快速地编码持续时间。讨论了可能维持幼年大鼠间隔计时的替代网络。
Interval timing refers to the ability to perceive, estimate and discriminate durations in the range of seconds to minutes. Very little is currently known about the ontogeny of interval timing throughout development. On the other hand, even though the neural circuit sustaining interval timing is a matter of debate, the striatum has been suggested to be an important component of the system and its maturation occurs around the third post-natal (PN) week in rats. The global aim of the present study was to investigate interval timing abilities at an age for which striatum is not yet mature. We used odor fear conditioning, as it can be applied to very young animals. In odor fear conditioning, an odor is presented to the animal and a mild footshock is delivered after a fixed interval. Adult rats have been shown to learn the temporal relationships between the odor and the shock after a few associations. The first aim of the present study was to assess the activity of the striatum during odor fear conditioning using 2-Deoxyglucose autoradiography during development in rats. The data showed that although fear learning was displayed at all tested ages, activation of the striatum was observed in adults but not in juvenile animals. Next, we assessed the presence of evidence of interval timing in ages before and after the inclusion of the striatum into the fear conditioning circuit. We used an experimental setup allowing the simultaneous recording of freezing and respiration that have been demonstrated to be sensitive to interval timing in adult rats. This enabled the detection of duration-related temporal patterns for freezing and/or respiration curves in infants as young as 12 days PN during odor fear conditioning. This suggests that infants are able to encode time durations as well as and as quickly as adults while their striatum is not yet functional. Alternative networks possibly sustaining interval timing in infant rats are discussed.