Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL 33410, USA.
Curr Biol. 2012 Jul 10;22(13):1247-52. doi: 10.1016/j.cub.2012.05.009. Epub 2012 May 31.
The global logic used by the brain for differentially encoding positive and negative experiences remains unknown along with how such experiences are represented by collections of memory traces at the cellular level. Here we contrast the cellular memory traces that form in the dorsal paired medial (DPM) neurons of Drosophila after conditioning flies with odors associated with aversive or appetitive unconditioned stimuli (US). Our results show that the appetitive DPM neuron trace is distinguished from the aversive in three fundamental ways: (1) The DPM neurons do not respond to an appetitive US of sucrose by itself, in contrast to their robust response to an aversive US. (2) The appetitive trace persists for twice as long as the aversive trace. (3) The appetitive trace is expressed in both neurite branches of the neuron, rather than being confined to a single branch like the aversive trace. In addition, we demonstrate that training flies with nonnutritive sugars that elicit a behavioral memory that decays within 24 hr generates, like aversive conditioning, a short-lived and branch-restricted memory trace. These results indicate that the persistence and breadth of the DPM neuron memory trace influences the duration of behavioral memory.
大脑用于区分编码正性和负性体验的全局逻辑尚不清楚，同样不清楚的还有这些体验如何在细胞水平上由记忆痕迹的集合来表示。在这里，我们对比了果蝇在与厌恶或奖赏非条件刺激（US）相关的气味条件下， Dorsal Paired Medial（DPM）神经元中形成的细胞记忆痕迹。我们的结果表明，奖赏性 DPM 神经元的记忆痕迹与厌恶性的有三个基本区别：（1）与强烈响应厌恶性 US 相比，DPM 神经元本身不会对奖赏性 US（蔗糖）做出反应。（2）奖赏性痕迹持续的时间是厌恶性痕迹的两倍长。（3）奖赏性痕迹在神经元的两个神经突分支中表达，而不像厌恶性痕迹那样局限于单个分支。此外，我们证明，用非营养性糖训练果蝇会产生一种在 24 小时内衰减的行为记忆，这种记忆与厌恶性条件作用一样，产生短暂且分支受限的记忆痕迹。这些结果表明，DPM 神经元记忆痕迹的持续时间和广度影响行为记忆的持续时间。
