Luu Paul, Sill Orriana C, Gao Lulu, Becker Suzanna, Wojtowicz Jan Martin, Smith David M
Department of Physiology, University of Toronto.
Behav Neurosci. 2012 Jun;126(3):381-91. doi: 10.1037/a0028252.
Adult neurogenesis in the hippocampal dentate gyrus plays an important role in learning and memory. However, the precise contribution of the new neurons to hippocampal function remains controversial. Emerging evidence suggests that neurogenesis is important for pattern separation and for mitigating interference when similar items must be learned at different times. In the present study, we directly test this prediction using a recently developed olfactory memory task that has those specific features. In this task, rats learn two highly interfering lists of odor pairs, one after the other, in either the same or in different contexts. Consistent with our hypothesis, focal cranial irradiation, resulting in selective reduction of neurogenesis within the dentate gyrus, significantly impaired the ability to overcome interference during learning of the second list. The ability to learn a single odor list was unimpaired. We also show that irradiation had no effect on learning in a hippocampal-dependent spatial alternation task. Although both tasks involved learning interfering responses, the time course for learning the interfering items differed. Learning the interfering odor lists took place sequentially, over the course of several sessions, whereas learning the interfering spatial locations took place concurrently, within each session. Thus, the gradual addition of new neurons may have provided a pattern separation mechanism for the olfactory task but not for the maze task. These findings demonstrate a role for neurogenesis in resolving interference and they are consistent with models suggesting a critical role for neurogenesis in pattern separation.
海马齿状回中的成体神经发生在学习和记忆中起着重要作用。然而，新生成的神经元对海马功能的确切贡献仍存在争议。新出现的证据表明，神经发生对于模式分离以及在必须在不同时间学习相似项目时减轻干扰很重要。在本研究中，我们使用最近开发的具有这些特定特征的嗅觉记忆任务直接检验了这一预测。在这个任务中，大鼠先后学习两组高度干扰的气味对列表，学习过程可以在相同或不同的环境中进行。与我们的假设一致，局部颅脑照射导致齿状回内神经发生选择性减少，显著损害了在学习第二组列表时克服干扰的能力。而学习单个气味列表的能力未受影响。我们还表明，照射对海马依赖性空间交替任务的学习没有影响。虽然这两个任务都涉及学习干扰性反应，但学习干扰项目的时间进程不同。学习干扰性气味列表是在几个实验阶段中依次进行的，而学习干扰性空间位置是在每个实验阶段中同时进行的。因此，新神经元的逐渐增加可能为嗅觉任务提供了一种模式分离机制，但对迷宫任务则不然。这些发现证明了神经发生在解决干扰方面的作用，并且与表明神经发生在模式分离中起关键作用的模型一致。
