There is now ample evidence that the strength and underlying mechanisms of memory formation can be drastically altered by prior experience. However, the prior work using rodent models on this topic has used only males as subjects, and as a result, we do know whether or not the effects of prior experience on subsequent learning are similar in both sexes. As a first step towards addressing this shortcoming, rats of both sexes were given auditory fear conditioning, or fear conditioning with unsignaled shocks, followed an hour or a day later by a single pairing of light and shock. Fear memory for each experience was assessed by measuring freezing behavior to the auditory cue and fear-potentiated startle to the light. Results showed that males trained with auditory fear conditioning showed facilitated learning to the subsequent visual fear conditioning session when the two training sessions were separated by one hour or one day. Females showed evidence of facilitation in rats given auditory conditioning when they were spaced by an hour but not when they were spaced by one day. Contextual fear conditioning did not support the facilitation of subsequent learning under any conditions. These results indicate that the mechanism by which prior fear conditioning facilitates subsequent learning differs between sexes, and they set the stage for mechanistic studies to understand the neurobiological basis of this sex difference.

现在有充分的证据表明，记忆形成的强度和潜在机制可以通过先前的经验而发生巨大改变。然而，之前在该主题上使用啮齿动物模型的工作仅使用男性作为受试者，因此，我们确实知道先前经验对后续学习的影响在两性中是否相似。作为解决这一缺点的第一步，对两种性别的大鼠进行听觉恐惧条件反射，或通过无信号电击进行恐惧条件反射，一小时或一天后进行单组光和电击。通过测量对听觉提示的冻结行为和对光的恐惧强化惊吓来评估每次经历的恐惧记忆。结果表明，当两次训练相隔一小时或一天时，接受听觉恐惧条件训练的男性表现出对随后的视觉恐惧条件训练的学习更容易。雌性老鼠在间隔一小时时显示出对听觉调节的促进作用，但在间隔一天时则没有。情境恐惧条件反射并不支持在任何条件下促进后续学习。这些结果表明，先前的恐惧调节促进随后学习的机制在性别之间存在差异，并且它们为机械研究了解这种性别差异的神经生物学基础奠定了基础。