Jones Nicholas G, Kemenes Ildikó, Kemenes György, Benjamin Paul R
Sussex Centre for Neuroscience, School of Biological Sciences, University of Sussex, Falmer, Brighton BN1 9QG, United Kingdom.
Curr Biol. 2003 Jun 17;13(12):1064-9. doi: 10.1016/s0960-9822(03)00380-4.
Most neuronal models of learning assume that changes in synaptic strength are the main mechanism underlying long-term memory (LTM) formation. However, we show here that a persistent depolarization of membrane potential, a type of cellular change that increases neuronal responsiveness, contributes significantly to a long-lasting associative memory trace. The use of a model invertebrate network with identified neurons and known synaptic connectivity had the advantage that the contribution of this cellular change to memory could be evaluated in a neuron with a known function in the learning circuit. Specifically, we used the well-understood motor circuit underlying molluscan feeding and showed that a key modulatory neuron involved in the initiation of feeding ingestive movements underwent a long-term depolarization following behavioral associative conditioning. This depolarization led to an enhanced single cell and network responsiveness to a previously neutral tactile conditioned stimulus, and the persistence of both matched the time course of behavioral associative memory. The change in the membrane potential of a key modulatory neuron is both sufficient and necessary to initiate a conditioned response in a reduced preparation and underscores its importance for associative LTM.
大多数学习的神经元模型都假定，突触强度的变化是长期记忆（LTM）形成的主要机制。然而，我们在此表明，膜电位的持续性去极化，这种增加神经元反应性的细胞变化类型，对持久的联想记忆痕迹有显著贡献。使用具有已识别神经元和已知突触连接性的无脊椎动物模型网络具有这样的优势，即这种细胞变化对记忆的贡献可以在学习回路中具有已知功能的神经元中进行评估。具体而言，我们利用了软体动物进食所依赖的已被充分理解的运动回路，并表明参与进食摄取运动起始的一个关键调节神经元在行为联想条件作用后经历了长期去极化。这种去极化导致单细胞和网络对先前中性的触觉条件刺激的反应性增强，并且两者的持续性与行为联想记忆的时间进程相匹配。关键调节神经元的膜电位变化对于在简化标本中引发条件反应既是充分的也是必要的，并突出了其对联想LTM的重要性。
